Geochemical Behavior of Disposed Radioactive Waste 9780841208278, 9780841210745, 0-8412-0827-1

Citation preview

ACS SYMPOSIUM SERIES 246

Geochemical Behavior of Disposed Radioactive Waste Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.fw001

G. Scott Barney, EDITOR Rockwell Hanford Operations

James D. Navratil, EDITOR Rockwell International Rocky Flats Plant

Wallace W. Schulz, EDITOR Rockwell Hanford Operations

Based on a symposium jointly sponsored by the Divisions of Nuclear Chemistry and Technology, Industrial and Engineering Chemistry, and Geochemistry at the 185th Meeting of the American Chemical Society, Seattle, Washington, March 20-25, 1983

American Chemical Society, Washington, D.C. 1984

Library of Congress Cataloging in Publication Data

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.fw001

Geochemical behavior of disposed radioactive waste. (ACS symposium series, ISSN 0097-6156; 246) "Based on a symposium jointly sponsored by the Divisions of Nuclear Chemistry and Technology, Industrial and Engineering Chemistry, and Geochemistry at the 185th Meeting of the American Chemical Society, Seattle, Washington, March 20-25, 1983." Bibliography: p. Includes index. 1. Radioactive waste disposal in the ground— Congresses. 2. Radioisotopes—Congresses. 3. Geochemistry, Analytic—Congresses. I. Barney, G. Scott. II. Navratil, James D., 1941. III. Schulz, Wallace W. IV. American Chemical Society. Division of Nuclear Chemistry and Technology. V. American Chemical Society. Division of Industrial and Engineering Chemistry. VI. American Chemical Society. Division of Geochemistry. VII. Series. TD898.G35 1984 ISBN 0-8412-0827-1

621.4838

83-3106

Copyright © 1984 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc., 21 Congress Street, Salem, M A 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA

American Chemical

Society Library 1155 16th St., N.W. Washington, D.C. 20036

ACS Symposium Series M . Joan Comstock, Series Editor

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.fw001

Advisory Board Robert Baker

Geoffrey D. Parfitt

U.S. Geological Survey

Carnegie-Mellon University

Martin L. Gorbaty

Theodore Provder

Exxon Research and Engineering Co.

Glidden Coatings and Resins

Herbert D. Kaesz

James C. Randall

University of California—Los Angeles

Phillips Petroleum Company

Rudolph J. Marcus

Charles N. Satterfield

Office of Naval Research

Massachusetts Institute of Technology

Marvin Margoshes

Dennis Schuetzle

Technicon Instruments Corporation

Ford Motor Company Research Laboratory

Donald E. Moreland USDA, Agricultural Research Service

Davis L. Temple, Jr. Mead Johnson

W. H. Norton J. T. Baker Chemical Company

Charles S. Tuesday General Motors Research Laboratory

Robert Ory USDA, Southern Regional Research Center

C. Grant Willson IBM Research Department

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.fw001

FOREWORD The ACS SYMPOSIUM SERIES was founded in 1974 to provide

a medium for publishing symposia quickly in book form. The format of the Series parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously published papers are not accepted. Both reviews and reports of research are acceptable since symposia may embrace both types of presentation.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.pr001

PREFACE FOR A COMPLEX TECHNOLOGY to reach a productive maturity, the disparate scientific disciplines underlying that technology must be gathered into a coherent whole. It is difficult to imagine a technology for which this is better exemplified than the geological disposal of radioactive wastes. The underlying scientific areas include surface chemistry (sorption-desorption, dissolution, ion exchange, corrosion), solution chemistry (hydrolysis, complexation, oxidation-reduction, precipitation), colloid chemistry, ceramics, metallurgy, hydrology, rock mechanics, and geology. These and other fields of study must be synthesized into a useful, practical whole through modelling and rational thought. Finally, the rationalized body of information and conclusions drawn must be substantiated by tests performed in the actual waste disposal environment. This volume makes an important contribution to the information needed for disposal of wastes in geological media, demonstrating the advanced state of knowledge in many of the above fields of research. It represents a major part of what must be known before high-level radioactive waste disposal may become a reality. Governmental agencies in the United States and other countries have sponsored a large amount of research on the behavior of radioactive wastes in various environmental settings. The overall objective of this research has been to protect the health and safety of the public by assessing the potential hazard of radionuclides in disposed wastes over periods of time when these radionuclides are significantly active. Making such an assessment requires an understanding of radionuclide distribution and inventory in or near the disposal site, and of the transport processes (chemical, physical, and biotic) that control the movement of radionuclides. The geochemistry of radionuclides in disposal environments is clearly one of the most important aspects of safety assessment because radionuclide release from the disposal site is controlled by complex chemical processes. The goal of this volume is to provide the reader with a single source of the most recent and significant findings of research on the geochemical behavior of disposed radioactive wastes. Radioactive wastes of concern include wastes that result from operation of the nuclear fuel cycle (mining, fuel fabrication, reactor operation, spent fuel reprocessing, and waste storage), from nuclear weapons testing, and from medical and research activities. In recent years, the emphasis has been on predicting the behavior of disposed high-level wastes in deep geologic vii

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.pr001

repositories. The many chapters on high-level waste reflect this emphasis. However, the chemical behavior of the individual radionuclides described will apply to many types of waste in geologic environments. The chapters of this volume are organized into sections that cover the chemical aspects that are important to understanding the behavior of disposed radioactive wastes. These aspects include radionuclide sorption and desorption, solubility of radionuclide compounds, chemical species of radionuclides in natural waters, hydrothermal geochemical reactions, measurements of radionuclide migration, solid state chemistry of wastes, and waste-form leaching behavior. The information in each of these sections is necessary to predict the transport of radionuclides from wastes via natural waters and thus to predict the safety of the disposed waste. Radionuclide transport in natural waters is strongly dependent on sorption, desorption, dissolution, and precipitation processes. Thefirsttwo sections discuss laboratory investigations of these processes. Descriptions of sorption and desorption behavior of important radionuclides under a wide range of environmental conditions are presented in thefirstsection. Among the sorbents studied are basalt interbed solids, granites, clays, sediments, hydrous oxides, and pure minerals. Effects of redox conditions, groundwater composition and pH on sorption reactions are described. Solubility constraints define the maximum concentrations of radionuclides at the point of release from the waste. In the second section, radionuclide solubilities in natural waters are reported as measured values and estimated values from thermodynamic data. In addition, information is given concerning the chemical species of radionuclides that could be present in natural waters. If the heat generated from the waste by radioactive decay is great enough (as in the case of high-level waste disposed of in deep geologic repositories), hydrothermal reactions will occur between the groundwater, host rocks, and waste. The resulting alteration of these solids and groundwaters will affect the behavior of radionuclides in these systems. In the third section, the effects of these hydrothermal reactions are described. Field measurements of radionuclide migration can be used to help substantiate laboratory measurements of sorption, solubility, and identification of important chemical species. The fourth section describes three field investigations that provide information on the effects of organics, colloids and environmental conditions (Eh, pH, and temperature) on radionuclide transport. The chemical species of radionuclides that are mobile under specificfieldconditions are identified. Solid state chemistry of potentially important waste forms is covered in thefifthsection. Solid state reactions can determine the oxidation state and physical and chemical stability of radionuclides in various host waste forms. This information can be used to evaluate the utility of crystalline materials as potential hosts for radioactive wastes. viii

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.pr001

Groundwater leaching of radionuclides from waste forms is thefirststep in radionuclide transport from a disposal site. The release rate of radionuclides from the waste form is dependent on the waste form's leaching behavior. The sixth section describes the factors that affect the leaching behavior of several potential waste forms and radionuclides. Finally, Mike McCormack, former Washington state Congressman, discusses the Federal legislation affecting nuclear waste disposal in the United States and the impact of several new laws passed by the Congress— the Nuclear Waste Policy Act of 1982 and the Low-Level Radioactive Waste Policy Act of 1980. This volume covers ongoing research and, thus, leaves many questions unanswered and many problems unsolved. The geochemistry of disposed radioactive wastes involves many complex issues that will require years of additional research to resolve. High-priority problems include: integration of geochemical data with computer models of chemical interaction and transport, definition of environmental conditions that affect the behavior of radionuclides at specific disposal sites, evaluation of complex formation of dissolved radionuclides with inorganic and organic complexants, and determination of radionuclide solubilities in natural waters. The editors would like to express their deep appreciation and admiration to Teresa Bess of Rockwell Hanford Operations whose editorial assistance greatly speeded the publication of this volume. G. SCOTT BARNEY

Rockwell Hanford Operations Richland, Washington JAMES D. NAVRATIL

Rockwell International Rocky Flats Plant Golden, Colorado WALLACE W. SCHULZ

Rockwell Hanford Operations Richland, Washington RAYMOND G. WYMER

Oak Ridge National Laboratory Oak Ridge, Tennessee December 1983

ix

1 Radionuclide Sorption and Desorption Reactions with Interbed Materials from the Columbia River Basalt Formation G. S. BARNEY

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

Rockwell International, Energy Systems Group, Richland, WA 99352

The sorption and desorption behavior of radionuclides in groundwater-interbed systems of the Columbia River basalt formation was investigated. Radionuclides chosen for study were those of concern in assessing the safety of a high-level radioactive waste repository in basalt (isotopes of technetium, neptunium, plutonium, uranium, americium, cesium, strontium, and radium). Sandstone and tuff materials from selected interbed layers between basalt flows were used in these experiments. Effects of groundwater composition and redox potential (Eh) on radionuclide sorption and desorption on the geologic solids were studied. Sodium, potassium, and calcium in the groundwater decrease sorption of cesium, strontium, and radium by ion exchange reactions. Groundwater Eh strongly affects sorption of technetium, neptunium, plutonium, and uranium since chemical species of these elements containing the lower oxidation states are more extensively sorbed by chemisorption than those containing higher oxidation states. Effects of radionuclide complexation by groundwater anions on sorption were not observed except for neptunium carbonate (or bicarbonate) complexes and plutonium sufate complexes. Sorption and desorption isotherms were obtained for sorption of radionuclides under oxidizing and reducing conditions. The Freundlich equation accurately describes most of these isotherms. Most radionuclides are apparently irreversibly sorbed on each of the geologic solids since the slopes of sorption and desorption isotherms for a given radionuclide are different. This hysteresis effect is very large and will cause a significant delay in radionuclide transport. It, therefore, should be included in modeling radionuclide transport to accurately assess the isolation capabilities of a repository in basalt. 0097-6156/84/0246-0003S06.00/0 © 1984 American Chemical Society

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

4

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

The groundwater transport of radionuclides through waterbearing interbed layers in the Columbia River basalt formation will be controlled by reactions of the radionuclides with groundwater and interbed solids. These interactions must be understood to predict possible migration of radionuclides from a proposed radioactive waste repository in basalt. Precipitation and sorption on interbed solids are the principle reactions that retard radionuclide movement in the interbeds. The objective of the work described herein was to determine the sorption and desorption behavior of radionuclides important to safety assessment of a highlevel radioactive waste repository in Columbia River basalt. The effects of groundwater composition, redox potential, radionuclide concentration, and temperature on these reactions were determined. Geochemical models of sorption and desorption must be developed from this work and incorporated into transport models that predict radionuclide migration. A frequently used, simple sorption (or desorption) model is the empirical distribution coefficient, Kd. This quantity is simply the equilibrium concentration of sorbed radionuclide divided by the equilibrium concentration of radionuclide in solution. Values of Kd can be used to calculate a retardation factor, R, which is used in solute transport equations to predict radionuclide migration in groundwater. The calculations assume instantaneous sorption, a linear sorption isotherm, and single-valued adsorption-desorption isotherms. These assumptions have been shown to be erroneous for solute sorption in several groundwater-soil systems (1-2). A more accurate description of radionuclide sorption is an isothermal equation such as the Freundlich equation: S = KC

N

(1)

where S = the equilibrium concentration of sorbed radionuclide in moles/g C = the equilibrium concentration of radionuclide in solution in moles/L K and N = empirical constants. This equation has been successfully applied to many sorption and desorption reactions of dissolved metals and organic compounds. In the case of irreversible sorption (hysteresis), sorption and desorption isotherms are not identical. However, both sorption and desorption Freundlich isotherm equations can be substituted into the transport equation(2): pS

dC _ Da c

t

ac

2

dt

dx

(2) dx

1.

BARNEY

Sorption and Desorption

where

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

D = dispersion coefficient v = average pore water velocity p = bulk density 0 = saturated water content x = distance in the direction of flow t = time. This equation can be used to describe one-dimensional transport of radionuclides through porous media (e.g. radionuclide elution curves from laboratory columns packed with interbed solids) assuming instantaneous sorption and desorption. Van Genuchten and coworkers have demonstrated the importance of using both sorption and desorption isotherms in this equation when hysteresis is significant. Isotherm data for sorption and desorption reactions of radionuclides with interbed materials are presented in this paper which can be used to predict radionuclide transport. Experimental Materials, The groundwater compositions of waters in the major water bearing zones of the Columbia River basalts at the Hanford Site have been determined (3). There are two distinct groundwaters present in the basalts: a sodium-bicarbonate buffered groundwater (pH 8 at 25°C) characteristic of the Saddle Mountains and Upper Wanapum basalts and a sodium-silicic acid buffered groundwater (pH 10 at 25°C) characteristic of the Lower Wanapum and Grande Ronde Basalts. Synthetic groundwater compositions have been established that simulate these two groundwater types. The compositions of the synthetic groundwaters used in the sorption experiments are given in Table I. The GR-1A groundwater simulates the groundwater composition of the Mabton Interbed in the Saddle Mountain Basalts. The GR-2 and GR-2A groundwaters simulate the dominant groundwaters in the Lower Wanapum and Grande Basalts. Synthetic groundwaters are used rather than actual groundwaters in order to ensure the availability of a stable, compositionally consistent groundwater for the sorption experiments. Three interbed materials from the Columbia River Basalt Group have been investigated in the radionuclide sorption experiments. Interbeds are porous sedimentary layers located between many of the basalt flows in the Columbia River Basalt Group and comprise a potential preferential pathway for groundwater and, therefore, radionuclide transport. Two interbed samples, a sandstone and a tuff, were taken from as outcrop of the Rattlesnake Ridge Interbed above the

5

6

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

Table I. Synthetic Groundwater Compositions Concentration (mg/L) Constituents GR-1A Na K

+

107

+

Ca

2 +

2 +

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

Mg ci-

2

C0 " 3

HCO3-

F2

so 4

Si0

GR-2A

225

246

11.2

2.5

2.5

2.0

1.06

1.01

0.4

0.07

0 152

50*

131

0

59

28.8

215

75

36.6

1.3

29

37

2.4

72

108

108

82

30

2

GR-2

pH

8.5

Ionic strength

-

10.0 0.014

10.0

-

*In experiments having reducing conditions, CI" content increased to 479 mg/L due to addition of HC1 to neutralize N H to obtain pH = 8.5. 2

4

Pomona basalt flow. A third interbed sample was taken from drilling cores of the Mabton Interbed, located between the Saddle Mountains and Wanapum Basalts. The Mabton Interbed is the first continuous, major interbed above the candidate repository horizons in the Grande Ronde Basalts. Mineralogical characteristics of the interbed materials are summarized in Table II. A more complete discussion of the characteristics of the interbed materials may be found in Reference (4). Procedures. Batch equilibrations of interbed solids (Mabton Interbed, Rattlesnake Ridge sandstone, or tuff), tracers, and groundwaters were used to measure radionuclide distributions between solid and liquid phases. Triplicate measurements were made for each combination of temperature, redox condition, tracer concentration, tracer type, groundwater composition, and interbed sample. Constant temperatures were maintained by placing the

not available

9.9 ± 0.2meq/100g Quartz Albite Anorthite Nontronite Biotite Orthoclase

Quartz Plagioclase Orthoclase Hornblende Muscovite Biotite

c

b

a

Clinopyroxene Illite (Also basalt fragments) Ethylene glycol method (5). Strontium cation exchange (6). By X-ray diffraction and electron microprobe.

Minerals present

6

Cation exchange capacity

0

not available

2

50.9 ± 0.8m /g

a

Surface area

16% = < 250 mesh 60% = 40 to 250 24% = t> O O O

CM CO 00 Ο Ο rH T-Î ϊ-ί rH

COOCO 0 0 5 0 H O r i

OOO) l O CO Ο Η Η Η

^ l O CO 05 05 rH Ο Ο rH

τ * rH 05 05 0 5 C ^ O O O

CO . C O Ο I CO '—ΐ

Ο Η O O

CO lO OCOCM H l O O

CO CO CO rH «tf ο O O O O O O

. Tt l O I t> CO rH

co o> co

(N(NH O O O O O O O O O

00 Ο t^fHCN Ο rH CM rH

CO ICO O O O O

CM 00 CO rH Ο Ο CO 00

05 05 Ο

co

050 , 05 05 I OO

05 CO 00 Ο Ο* rH

ο C005 Ο 00 OCM

2 S3 cd

CO Ο LO CM CO OO

CO Ο LO CM CO 00

CO Ο LO CM CO 00

bo

bo

CO Ο LO CM CO 00

CO Ο LO CM CO 00

CO Ο LO CO Ο LO CO Ο LO CM CO 00 CM CO 00 CM CO 00

bo

bo

bo

ε

bo

•ι—I

ο

Ν

ο

X

ο

bo G

bO ο

"ο 0)

Pi

ο

eu

'S Ph

a>

e 'S

3 C! ο (η

cd

CO

0)

CO

s ce

ε

ε *s

'S

PU

_2 ci

u

ε "Π

ε




ο

ο

12

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

Tin and americium were so extensively sorbed under all conditions that isotherm data could not be obtained. These elements are not significantly mobile in the Mabton Interbed aquifer. Values of Freundlich constants for technetium, radium, uranium, neptunium, and plutonium are given in Table IV. The Freundlich equation did not fit the selenium sorption data very well probably because of slow sorption kinetics or precipitation. Precipitation was also observed for technetium at 23°C for concentrations above 10" M. This is about the same solubility observed for technetium in the sandstone isotherm measurements. Linear isotherms were observed only in the case of radium sorption. In general, sorption on the Mabton Interbed was greater than on the Rattlesnake Ridge sandstone. This is probably due to the greater clay content of the Mabton standard. The Freundlich equation requires the assumption that sorption reactions are reversible. However, several studies (7) have recently shown that Κ and Ν depend on sorption direction, i.e., whether sorption or desorption occurred. In each case, Ν was less and Κ was greater for desorption than sorption. This chemical hysteresis will, of course, affect radionuclide transport. For example, if hysteresis occurs during a column experiment in which a pulse of tracer is added to the influent, the effluent curve will show heavy tailing and a reduction in peak concentration. Ignoring hysteresis effects could cause serious errors in predicting radionuclide movement. Desorption isotherms for selenium, technetium, neptunium, uranium, and radium have been measured for the Mabton Interbed materials under both oxidizing and reducing conditions at 60°C using the Grande Ronde groundwater composition, GR-1A. The reason for measuring desorption isotherms is to determine whether or not the sorption reactions are reversible (i.e., exhibit hysteresis). An example of the results of desorption isotherm measurements is shown in Figure 2. These curves are Freundlich plots of the sorption and desorption data for neptunium at 60°C under oxidizing and reducing conditions. The two desorption curves were obtained using different tracer loadings (initial S values). Both plots show hysteresis since the slopes of the desorption curves are less than the sorption curves. Hysteresis is a much greater effect for neptunium sorption under reducing conditions, however. The ratio of Freundlich exponents Ns/Nd, where N and Nd are the measured exponents for sorption and desorption, respectively, is a measure of the magnitude of hysteresis. Larger values for Ng/Nd indicate greater hysteresis effects. For neptunium sorption under oxidizing conditions Ng/Nd = 2 and for reducing conditions Ng/Nd = 435. The sorption and desorption behavior of uranium is similar to neptunium. Figure 3 shows that hysteresis is more important for uranium sorption under reducing conditions than under oxidizing conditions. Values of Ns/Nd are 10 and approximately 200 for oxidizing and reducing conditions, respectively.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

7

s

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch001

1.

BARNEY

Sorption and Desorption

13

000500^* 0 0 0 0 05050505 0 0 0 0

H Q ^ t O I> rH C75 C75 05050505 0 0 0 0

CO CM C> O 05 05 05 05 05050505 O O O O

Ttt^ÇOiO 05 05 05 05 05 0 5 0 5 0 5 Ο Ο Ο Ο

Ο CO t> 05 ° 0 Ο Ο

τΗΟ5Ο500 05 05 Ο ΙΟ OOrHO*

00 05 rH 00 rH 05 05 05 rH ο Ο Ο

τ * CO 00 θ 5 t> 05 00 l > 0 0 * 0 0*

05 00 0 0 CO CO 00 00 Ο O O O

LO 00 05 t> ο* ο*

Tf

— 5, i n d i c a t i n g reducing c o n d i t i o n s . 1

38

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

\

•

ο υ Η 0.6 1

Magnetite Goethite Ilmenite Limonite Spec. Hematite Nat. Hematite Synth. Hematite Iron Metal

\ ι—I

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

0.4

10

15

20

30

25

t (days)

0

5

10

15

20

25

30

t (days)

FIGURE

7.

Decrease

in

time

for

solutions

technetium

iron

minerals

under

concentration

i n contact (a)

oxic

as a f u n c t i o n

with iron and (b)

metal

anoxic

of

and

conditions.

2.

Reactions Between Tc and Fe-Containing Minerals 39

VANDERGRAAF ET AL.

i 2

Initial [ T c ] : 3 x l d m o l / L Distilled Oeionized Water Granite Groundwater WN-I Saline Solution Std. Can. Shield Sal. S o i n 2

HPO4-

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

mic Acid -

10

20

30

I40mg/L

lOOmg/L

50

40

t (days)

Initial C T c D : l O "

20

4

mol/L

30 (tjdays

F I G U R E 8.

Decrease i n technetium c o n c e n t r a t i o n as a f u n c t i o n time for s i x s o l u t i o n s i n contact w i t h magnetite (FeO.Fe2Û3). I n i t i a l technetium concentration 3 χ 1 0 " m o l / L ( a ) a n d l x 10" mol/L (b). 1 2

of

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

40

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

Discussion The r e s u l t s obtained f o r crushed g r a n i t e and gabbro under o x i c c o n d i t i o n s , compared to those obtained f o r the acid-washed quartz (see Table I I I ) , c l e a r l y show that no s i g n i f i c a n t s o r p t i o n takes place on g r a n i t e , but that some technetium can be removed from s o l u t i o n by gabbro. Since small amounts (< 20 mg) of m e t a l l i c i r o n are able to remove as much as 99+% of the technetium from s o l u t i o n , any s o r p t i o n observed f o r g r a n i t e over the time s c a l e of the experiment may be a t t r i b u t e d to the presence of m e t a l l i c i r o n , i n a d v e r t e n t l y introduced i n the crushing and g r i n d i n g processes. In the absence of oxygen, again no s i g n i f i c a n t s o r p t i o n was noted f o r g r a n i t e . However, i n one case, some s o r p t i o n was observed f o r gabbro. Pétrographie a n a l y s i s of the area of the gabbro coupon that showed s o r p t i o n , as revealed by an autoradiograph (Figure 3 ) , i n d i c a t e d the presence of a t h i n i r o n - o x j ^ e band. Thus, even though gabbro contains ^ 4 2 % pyroxene ((Ca,Fe )SiOg), the ferrous i r o n i n t h i s mineral i s not able to remove the technetium from s o l u t i o n as e f f e c t i v e l y as the smaller amount of "opaques" ( i r o n oxides and i l m e n i t e ) . The i r o n oxide i s not d i s t r i b u t e d homogeneously throughout the gabbro rock matrix, and t h i s accounts f o r the wide v a r i a t i o n i n technetium removal from one coupon to the next. Crushing the rock f r e e s these opaques and d i s t r i b u t e s them more uniformly, and i t i s most l i k e l y that t h i s m a t e r i a l i s r e s p o n s i b l e f o r the s i g n i f i c a n t k^ values obtained with crushed gabbro under oxic c o n d i t i o n s . The autoradiographs of the rock and mineral t h i n s e c t i o n s (Figures 4 to 6) a l s o con££rm the importance of i r o n oxides: although b i o t i t e (K(Mg,Fe ) ^ S i ^ A 1 0 . ( 0 H ) ) and hornblende ((Na,Ca )(Mg,Fe ) ( A l , F e ) I S i ^ A 1 0 ^ ) ( O H ) ) contain ferrous i r o n , s o r p t i o n appears to take place s o l e l y on the small opaque ( i r o n - o x i d e ) i n c l u s i o n s . In the case of b i o t i t e , these oxides are l o c a t e d between the basal planes, and are randomly d i s t r i b u t e d i n the hornblende. S i m i l a r d i s t r i b u t i o n s are observed f o r o l i v i n e , pyroxene, and epidote. The r e s u l t s f o r pyroxene f u r t h e r confirm the low s o r p t i o n r e s u l t s obtained with gabbro, where i t i s one of the major m i n e r a l s . The autoradiographs a l s o show some s o r p t i o n on the g r a n i t e obtained from the Eye-Dashwa Lakes pluton ( F i g u r e 6 ) . Even though the i r o n c o n c e n t r a t i o n i s low, hydrothermal a l t e r a t i o n of the g r a n i t e has r e s u l t e d i n the i n f i l l i n g of the minute f r a c t u r e s i n the m i c r o c l i n e f e l d s p a r with i r o n oxides, which show technetium s o r p t i o n , while there i s no s o r p t i o n on the b i o t i t e c r y s t a l s . Thus, while f r e s h , unaltered g r a n i t e matrix rock has l i t t l e or no i r o n i n the form of i r o n oxides, a l t e r a t i o n zones around f r a c t u r e s do, and technetium s o r p t i o n may occur there. I t should a l s o be noted that s o r p t i o n of technetium i s l i m i t e d to s p e c i f i c mineral s u r f a c e s . Thus, i t appears that the r e d u c t i o n of TcO, to a lower o x i d a t i o n s t a t e occurs at or near the surface of the Iron oxide and not i n the bulk of the s o l u t i o n , by d i s s o l v e d f e r r o u s i o n s . n

2

?

2

2

2.

VANDERGRAAF ET AL.

Reactions Between Tc and Fe-Containing Minerais 41

The experiment i n v o l v i n g a s u i t e of iron-oxide minerals showed t h a t , with the exception of the s y n t h e t i c hematite, some s o r p t i o n took place on a l l minerals under anoxic c o n d i t i o n s and a l s o , i n some cases, i n the presence of a i r ( F i g u r e s 7(a) and (b)). Subsequent chemical analyses i n d i c a t e d small amounts of F e ( I I ) i n a l l n a t u r a l minerals, although g o e t h i t e , l i m o n i t e , and hematite should not contain any. These minerals may have been formed by the o x i d a t i o n and hydration of magnetite (FeO Fe 0^) and therefore contain r e s i d u a l amounts of unoxidized F e ( I I ) . At any r a t e , t h i s points out the importance of using p u r i f i e d and/or chemically analyzed m a t e r i a l . I t i s again noteworthy that the r a t e of s o r p t i o n on i l m e n i t e i s lower than that on n a t u r a l hematite, even though the former contains more F e ( I I ) . This can again be explained i n terms of a v a i l a b i l i t y of the ferrous i r o n , as was shown to be the case with the t h i n s e c t i o n s . Sorption on magnetite as a f u n c t i o n of groundwater composition shows that, under anoxic c o n d i t i o n s , technetium removal from s o l u t i o n i s e s s e n t i a l l y complete a f t e r 50 days, with the exception of s o l u t i o n s containing phosphate i o n s . As pointed out e a r l i e r , phosphate was used instead of carbonate, as both are known to form a n i o n i c complexes with Tc(IV) ( 9 ) . In these s t u d i e s , the presence of humic a c i d d i d not a f f e c t i t s s o r p t i o n . Strong s a l i n e s o l u t i o n s (up t o 34 000 mg/L CI) do not have a marked e f f e c t on the rate of technetium removal from s o l u t i o n e i t h e r , as evident from Figure 8.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

e

Conclusions The r e s u l t s reported i n t h i s paper show that technetium i s removed from s o l u t i o n by i r o n oxides, and not by minerals c o n t a i n i n g ferrous i r o n as an i n t e g r a l part of t h e i r c r y s t a l l a t t i c e , such as b i o t i t e , pyroxene, or hornblende. I t was shown that there are cases where the small amount of i r o n i n g r a n i t e has a greater e f f e c t i n removing technetium from s o l u t i o n than the l a r g e r amounts of i r o n i n gabbro. Reduction of technetium occurs c l o s e to the mineral surface, and not i n the bulk of the s o l u t i o n , by d i s s o l v e d f e r r o u s i o n s . Technetium i s removed from groundwaters having widely d i f f e r e n t l e v e l s of t o t a l d i s s o l v e d s o l i d s , and i t s removal i s only a f f e c t e d by ligand-forming anions with a strong a f f i n i t y f o r technetium, such as phosphate (and presumably a l s o carbonate)· The s i g n i f i c a n c e of t h i s study f o r nuclear f u e l waste d i s p o s a l i s that i r o n - o x i d e - c o n t a i n i n g f r a c t u r e s i n hydrothermally a l t e r e d g r a n i t e are capable of sorbing technetium. Technetium transport i n the f a r - f i e l d region of a waste d i s p o s a l v a u l t can thus be impeded by iron-oxide coatings on h y d r o l o g i c a l l y conducting f r a c t u r e s u r f a c e s . I f necessary, r e t e n t i o n of technetium i n the n e a r - f i e l d region can be improved by i n c o r p o r a t i n g rock containing l a r g e amounts of i r o n oxides i n the b a c k f i l l material.

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

42

The presence of s a l i n e s o l u t i o n s at depth i n plutons i n the Canadian S h i e l d (11) should not be d e t r i m e n t a l t o r e t a i n i n g technetium i n the v a l u t s i n c e the experiments showed that technetium removal occurs from h i g h l y s a l i n e s o l u t i o n s . Throughout t h i s paper, r e f e r e n c e has beem made to reduced technetium s p e c i e s . Although i t has been assumed that Tc(IV) i s formed, there i s no d i r e c t evidence f o r t h i s . Experiments are now underway to determine the nature of the sorbed species u s i n g F o u r i e r Transform I n f r a r e d Spectroscopy, ?

Acknowl e dgment s The authors would l i k e to acknowledge the a s s i s t a n c e of J . Paquette and N. G a r i s t o i n p r o v i d i n g the E -pH diagrams f o r technetium and i r o n and of D,C. Kamineni, who performed the pétrographie analyses. The minerals from the GSC were obtained through i t s c u r a t o r , H.R. Steacy. R.F. Hamon, B.L. S a n i p e l l i and K. Ross performed the v a r i o u s chemical analyses reported i n t h i s paper.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

n

Literature Cited 1. 2.

3. 4. 5. 6. 7.

8.

9.

Clegg, L. J; Coady, J. R., "Radioactive Decay Properties of CANDU fuel Volume 1. The Natural Uranium Fuel Cycle," AECL-4436/1, Chalk River, Ontario, Canada, 1977. Palmer, D. Α.; Meyer, R. Ε., "Adsorption of Technetium on Selected Inorganic Ion-Exchange Materials and on a Range of Naturally Occurring Minerals under Oxic Conditions," J. Inorg. Nucl. Chem. 1981, 43, 2979. Allard, B; Kipatsi, H.; Torstenfelt, Β., Radiochim. Radioanalyt. Letters, 1979, 37, 233. Sheppard, M. I.; Vandergraaf, T. T.; Thibault, I. M.; Reid, J. Α. Κ., Accepted for publication in Health Physios. Landa, E. R.; Thorvig, L. M.; Gast, R. H., J. Environ. Qual. 1977, 6, 181. Bondietti, Ε. Α.; Francis, C. W., Science 1979, 203, 1337. White, D. E.; Hem, J. D.; Waring, G. Α., "Chemical Composition of Subsurface Waters," In: M. Fleischer (Editor), Data of Geochemistry, U.S. Geolog. Survey Prof. Paper, 440-F, 6th ed. 66 pp. 1963. Analytical Science Branch, "Chemical Analysis of the Initial Groundwater Samples from the Lac du Bonnet Batholith," Whiteshell Nuclear Research Establishment, Pinawa, Manitoba, Canada, 1979. Paquette, J . ; Reid, J. A. K.; Rosinger, E. L. J., "Review of Technetium Behavior in Relation to Nuclear Waste Disposal," TR-25, Whiteshell Nuclear Research Establishment, Pinawa, Monitoba, Canada, 1980.

2. VANDERGRAAF ET AL. Reactions Between Tc and Fe-Containing Minerals 43

10. 11.

Vandergraaf, T, T.; Abry, D.R.M.; Davis, C. E, Chem. Geol. 1982., 36, 139. Fritz, P.; Frape, S. K. Chem. Geol., 1982, 36, 179.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch002

RECEIVED October

20, 1983

3 Radionuclide Sorption Mechanisms and Rates on Granitic Rock Determination by Selective Chemical Extraction Techniques F. B. WALTON, T. W. MELNYK, J. P. M. ROSS, and A. M. M. SKEET Atomic Energy of Canada Limited, Whiteshell Nuclear Research Establishment, Pinawa, Manitoba R0E 1L0 Canada

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

137

144

75

The gamma-emitting radionuclides Cs, Ce, Se and Co were simultaneously contacted with granite from the Lac du Bonnet batholith using both static and dynamic methods. Selective chemical extraction was then used to differentiate between the amounts of sorbed radionuclides that are (a) readily ionexchangeable, (b) associated with amorphous oxyhydroxide deposits, and (c) "fixed" by other mineralogical or physical processes. Comparison of the experimental results from the dynamic tests with calculations from single sorption site kinetic models, using a variety of isotherms, showed that the models did not adequately describe the sorption reactions. Use of double sorption site models greatly improved the ability to describe solution concentrations and radionuclide surface inventories measured by extraction methods. Laboratory alteration of fresh granite surfaces was found to affect the sorption capacities and ratios of Co, Se and Ce. Granite alteration on a laboratory time scale had no effect on Cs sorption. Rate constants determined for the various processes indicate that under oxidizing conditions ionexchange processes are rapid, with equilibrium achieved within days. Reactions with oxyhydroxides or other mineralogical or physical processes take longer to achieve equilibrium, but, on time scales relevant to groundwater flow rates, will provide more significant retardation of the radionuclide migration than ion exchange. 60

60

144

137

0097-6156/ 84/ 0246-0045S06.25/ 0 © 1984 American Chemical Society

75

46

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

The l o c a t i o n and p h y s i c a l complexity of hard-rock f r a c t u r e systems make i t d i f f i c u l t to determine the mechanisms a f f e c t i n g r a d i o n u c l i d e m i g r a t i o n under f i e l d c o n d i t i o n s . Techniques are needed that, under c l o s e l y c o n t r o l l e d c o n d i t i o n s , provide data r e l e v a n t to mass transport i n the f i e l d . Development of two such techniques i s described here. Knowledge of s o r p t i o n k i n e t i c s i s e s s e n t i a l f o r the design of l a b o r a t o r y or f i e l d r a d i o n u c l i d e m i g r a t i o n experiments. There are two requirements f o r the r e t a r d a t i o n of r a d i o n u c l i d e migration: f i r s t , an i n t e r a c t i o n between the r a d i o n u c l i d e and the g e o l o g i c m a t e r i a l , and second, s u f f i c i e n t time f o r the i n t e r a c t i o n to occur. C r i t e r i a f o r assessing the l a t t e r requirement have been developed (1) i n terms of a dimensionless s o r p t i o n rate parameter 3 kAt /V, where k i s the s o r p t i o n ( f i r s t order) r a t e constant, t i s tîîe water t r a n s i t time (the time taken f o r w groundwater to flow between two observation p o i n t s ) , and A/V i s the r a t i o of the g r a n i t e surface area to the groundwater volume. The degree of r e t a r d a t i o n provided by a given chemical mechanism i s r e l a t e d not only to the e q u i l i b r i u m d i s t r i b u t i o n parameter, k , but a l s o to the s o r p t i o n rate parameter, 3. For instance, a pulse i n j e c t i o n of a r a d i o n u c l i d e w i l l t r a v e l with the groundwater and d i s p l a y only t a i l i n g f o r 0.1 < β < 1. On the other hand, complete r e t a r d a t i o n , according to the value of k can be assumed f o r 3 > 100. For intermediate values of 3, k i n e t i c peak broadening w i l l occur. In these s t u d i e s a dynamic t e s t i n g method (the m i x i n g - c e l l ) has been used to measure the s o r p t i o n k i n e t i c s of 4 d i f f e r e n t r a d i o n u c l i d e s on Lac du Bonnet g r a n i t e from the Archean Superior Province of the Canadian S h i e l d . This method has been used p r e v i o u s l y (2) f o r measurement of s o r p t i o n k i n e t i c s without the i n t e r f e r e n c e of h y d r a u l i c d i s p e r s i o n common i n many other dynamic techniques· A v a r i e t y of chemical e x t r a c t i o n techniques has been developed by s o i l s c i e n t i s t s to determine q u a n t i t a t i v e l y the amount of trace metals bound to s o i l p a r t i c l e s by various mechan­ isms. Multimechanism s o r p t i o n has been suggested i n order to e x p l a i n p a r t i a l i r r e v e r s i b i l i t y of r a d i o n u c l i d e s o r p t i o n and i n ­ creased s o r p t i o n with exposure time. The f i v e main s o r p t i o n mechanisms that have been reported a r e :

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

s

fl

1. 2. 3. 4. 5.

exchange with CaCl^ or M g C l , binding by carbonates, binding by organic compounds, s o r p t i o n by i r o n or manganese oxyhydroxides, and r e s i d u a l or " f i x e d " m a t e r i a l . 2

Since the m i x i n g - c e l l experiments were conducted with f r e s h or s l i g h t l y weathered g r a n i t e s u r f a c e s , techniques f o r determin­ ing s o r p t i o n by carbonates and organic compounds were omitted. Using e x t r a c t i o n techniques to determine r a d i o n u c l i d e sorbed by

3.

WALTON ET AL.

Radionuclide Sorption Mechanisms and Rates

47

mechanisms 1, 4 and 5 above on both m i x i n g - c e l l s and g r a n i t e coupons, i t was found that r a d i o n u c l i d e s o r p t i o n can be c o n s i d e r ­ ed q u a n t i t a t i v e l y to i n v o l v e at l e a s t two mechanisms with varying rates of r e a c t i o n . In a d d i t i o n , rock a l t e r a t i o n k i n e t i c s p a r t i c u l a r l y when f r e s h rock i s used - were found to s t r o n g l y a f f e c t the s o r p t i o n of some r a d i o n u c l i d e s .

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

Theory and S o r p t i o n Models In order to assess the f e a s i b i l i t y of any nuclear waste d i s p o s a l concept, mathematical models of r a d i o n u c l i d e s o r p t i o n processes are r e q u i r e d . In a l a t e r s e c t i o n k i n e t i c d e s c r i p t i o n s of the three common s o r p t i o n isotherms (3) are compared with experiment­ a l data from the m i x i n g - c e l l t e s t s . For a r a d i o n u c l i d e of con­ c e n t r a t i o n C i n the groundwater and concentration S on the sur­ face of the g r a n i t e , the net r a t e of s o r p t i o n , by a f i r s t - o r d e r r e v e r s i b l e r e a c t i o n , i s given by dS/dt » k C - k S x

(1)

2

where k, and k~ are the s o r p t i o n and desorption r a t e constants r e s p e c t i v e l y , V i s the f l u i d volume and A i s the g r a n i t e surface area. For a F r e u n d l i c h isotherm the net r a t e of s o r p t i o n can be expressed as dS/dt = k.C (C/C ) l o o

n

- k S

(2)

0

I

where η i s a constant and C i s the i n i t i a l t r a c e r concentration i n the groundwater. ° For a Langmuir s o r p t i o n isotherm the net s o r p t i o n r a t e can be written dS/dt = k.C(S - S)/S - k S ι ο ο ζ 0

(3)

where S i s the maximum surface concentration of r a d i o n u c l i d e . As w i l l be shown l a t e r , s o r p t i o n of most r a d i o n u c l i d e s may be a f u n c t i o n of two or more mechanisms. The combination two f i r s t - o r d e r r e a c t i o n s has been s u c c e s s f u l l y a p p l i e d to Sr m i g r a t i o n over a twenty-year time period i n a sandy-aquifer ( 1 ) . The equations d e s c r i b i n g two p a r a l l e l f i r s t - o r d e r r e a c t i o n s are S = S, + S dS /ά\ = k*C - k ^ dS^/dt = k^C - k^S χ

2

[ ,

(4)

The theory and v e r i f i c a t i o n of the m i x i n g - c e l l mass balance equation has been reported p r e v i o u s l y ( 2 ) . For a c e l l with i n i t i a l concentration of t r a c e r , C . flushed with t r a c e r - f r e e ο water at a volumetric r a t e , W, the mass balance i s given by

American Chemical Society Library 1155 16th St., N.W. Washington, D.C. 20036

48

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

VdC/dt - -WC

- A(dS/dt)

For the s p e c i a l case of a non-reactive Equation 5 gives C(t)/C

Q

» exp(-tW/V)

(5) t r a c e r , i n t e g r a t i o n of

(6)

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

Experimental A c t i v e Coupon Experiments* Coupons (19.8 χ 19.8 χ 4.00 mm) of Lac du Bonnet g r a n i t e , obtained from the Cold Spring Quarry near the W h i t e s h e l l Nuclear Research Establishment (WNRE), Pinawa, Manitoba, were exposed to g r a n i t e groundwater anji brings ço^taining^ghe gamma-emitting n u c l i d e s Cs, Ce, Se, Sb, Sn and Co. Pétrographie and chemical analyses of the g r a n i t e are given i n Table I ( 4 ) . Radionuclides were obtained c a r r i e r - f r e e from New England Nuclear. Groundwater compositions and r a d i o n u c l i d e s t a r t i n g concentrations are given i n Tables I I am} I I I . A rock surface area to s o l u t i o n volume r a t i o of ^ 1 cm /mL, approximately the same as the r a t i o i n the m i x i n g - c e l l experiments, was used i n these t e s t s . The f o l l o w i n g procedures, i n order of a p p l i c a t i o n , were used to determine the l o c a t i o n s and q u a n t i t i e s of r a d i o n u c l i d e s a s s o c i a t e d with v a r i o u s s o r p t i o n mechanisms: 1.

2.

3. 4.

5.

6.

7.

The coupons were contacted with g r a n i t e groundwater or b r i n e c o n t a i n i n g s i x r a d i o n u c l i d e s f o r 28 d. The coupons were removed and the s o l u t i o n s assayed to determine the amount of sorbed r a d i o n u c l i d e s . The coupons were contacted with t r a c e r - f r e e groundwater s o l u t i o n s , which were assayed a f t e r 28 d to determine the amount of a c t i v i t y that i s r e v e r s i b l y bound to the g r a n i t e under normal groundwater c o n d i t i o n s . The coupons were contacted with 0.5 mol/L CaCl« s o l u t i o n f o r 72 h to d i s p l a c e a l l remaining exchangeable r a d i o n u c l i d e s . The coupons were contacted f o r 24 h with a s o l u t i o n (termed KTOX) c o n t a i n i n g 0.1 mol/L potassium t e t r a o x a l a t e and 0.1 mol/L hydroxylamine hydrochloride to remove r a d i o n u c l i d e s a s s o c i a t e d with i r o n and manganese oxyhydroxides. The coupons were contacted with b o i l i n g Na^CO^ s o l u t i o n (5 wt%) f o r 15 min to remove r a d i o n u c l i d e s a s s o c i a t e d with hydrated s i l i c a t e s . The coupons were contacted f o r a second 48 h period with KTOX s o l u t i o n to remove some of the r a d i o n u c l i d e s a s s o c i a t e d with l a t t i c e s u b s t i t u t i o n into iron-bearing minerals. The coupons were gamma counted to determine r e s i d u a l or f i x e d activity.

I n a c t i v e Coupon Experiments. A f r e s h cut surface of Lac du Bonnet g r a n i t e contains both a l t e r e d and unaltered ferromagnesian

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

3.

WALTON ET AL.

Radionuclide Sorption Mechanisms and Rates

49

minerals ( 4 ) . Exposing the unaltered or p a r t i a l l y a l t e r e d phases to groundwater s o l u t i o n s during an experiment w i l l produce f u r t h e r phase a l t e r a t i o n . Since KTOX s o l u t i o n s e l e c t i v e l y d i s s o l v e s oxyhydroxide phases, i t can be used to monitor t h e i r production d u r i n g a l t e r a t i o n . A second s e r i e s of i n a c t i v e e x p e r i ­ ments was performed to study a l t e r a t i o n r a t e s of f r e s h g r a n i t e coupon s u r f a c e s . The coupons were u l t r a s o n i c a l l y cleaned and placed i n a s o l u t i o n of GGW f o r 101 d. They were then leached with KTOX s o l u t i o n f o r incremental times of 1,2,3,6,12,24,24 and 48 h, with the s o l u t i o n being renewed at each time i n t e r v a l . The same e x t r a c t i o n procedure was a p p l i e d to f r e s h l y cut coupons. The KTOX s o l u t i o n s were analyzed by i n d u c t i v e l y coupled plasma (ICP) spectrophotometry f o r i r o n i n order to c a l c u l a t e oxyhydroxide e x t r a c t i o n r a t e s as a f u n c t i o n of cumulative exposure to KTOX s o l u t i o n . 2 A g r a n i t e surface area to e x t r a c t i o n s o l u t i o n volume of * 1 cm /mL was used i n a l l e x t r a c t i o n procedures.

Table I .

M i n e r a l and Chemical Composition of Lac du Bonnet G r a n i t e (4)

Mineral

Modal Percent

Oxide

Weight Percent

Quartz

25.8

sio

K-feldspar

28.1

A1 0

Plagioclase

33.9

FeO

0.81

F e

0.76

73.1

2

2

3

14.2

Biotite

5.2

Muscovite

2.5

2°3 CaO

Opaques

0.7

MgO

Epidote

1.5

Na 0

4.23

Chlorite

2.3

κο

4.88

0.46 2

2

Tio

2

0.03

H0

n.d.

co 100.0

0.22

MnO 2

Total

1.43

2

Total

n.d. - below l e v e l of d e t e c t i o n

n.d. 100.09

50

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

Table I I . Groundwater Compositions (mg/L) *1

Brine

GGW +

Na K

+

Mg

2 +

Ca

2 +

Sr

2 +

F

5,050

3.5

50

3.9

200 15,000

13

-*2

e

t Si

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

8.3

HCO; Cl~ 2

20

15 10

5.0

34,260

so " 4 NO^

8.6

790

0.62

50

F~

0.19

-

pH

6.5±0.5

7±0.5

*1 ^2 GGW g r a n i t e groundwater In e q u i l i b r i u m with C0^ i n atmosphere s

Table I I I .

C a r r i e r - F r e e Radionuclide S t a r t i n g Concentrations Isotope

Starting,concentration (10 Bq/mL)

*Jco

26.9

t~ Ce ti'cs

53.3 27.7

7

n

*

Specific U 4

Ce

5.2Ί0

2.05 1.37 0.347

a c t i v i t i e s of isotopes i n Bq/g are:

- 1.2Ί0 1 4

*ÎSb ^Se Sn

;

1 1 3

1 4

;

1 3 7

Cs

- 3.2Ί0

Sn - 3.7Ί0

1 2

;

1 2 5

60 13 Co - 4.2·10 ;

Sb - 3.9Ί0

1 3

;

7 5

Se -

1 4

M i x i n g - C e l l Experiments. A schematic diagram o f a t y p i c a l c e l l used i n these experiments i s shown i n Figure 1. The c e l l s are

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

3.

WALTON ET AL.

Radionuclide Sorption Mechanisms and Rates

51

c i r c u l a r i n c r o s s - s e c t i o n and are f a b r i c a t e d by a double diamondd r i l l c o r i n g operation on a s l a b of Lac du Bonnet g r a n i t e . Two sets of experiments were conducted using s i x r a d i o a c t i v e t r a c e r s simultaneously. S t a r t i n g concentrations are given i n Table I I I . Radionuclides were e l u t e d from the c e l l s with groundwater s o l u t i o n s using a p e r i s t a l t i c pump. E f f l u e n t was c o l l e c t e d at 90-min i n t e r v a l s by means of a f r a c t i o n c o l l e c t o r connected to the c e l l with small-bore T e f l o n tubing. Concentrations of the various isotopes i n the e f f l u e n t were measured by gamma spectrometry. In the f i r s t set of experiments, s i x c e l l s were u l t r a s o n i c a l l y cleaned to remove rock powder produced during c o r i n g , and then f l u s h e d before t r a c e r i n j e c t i o n . Three were f l u s h e d with GGW and three with b r i n e . A second set of experiments was designed to determine whether mineral a l t e r a t i o n ratés and/or s o l u t i o n temperature a f f e c t the r a t e of r a d i o n u c l i d e i n t e r a c t i o n w i t h g r a n i t e . (Test c o n d i t i o n s a r e given i n Table VI o f the Results S e c t i o n ) . The 60°C temperature was maintained by submerging the c e l l s i n a water bath. Two c e l l s were f l u s h e d with GGW f o r s e v e r a l weeks and then allowed t o s i t , f i l l e d with GGW, f o r approximately f i v e months before the experiment was s t a r t e d . A f t e r both sets of experiments were completed, the groundwater was drained from the c e l l s and s e l e c t i v e chemical e x t r a c t ions of the g r a n i t e c e l l walls were performed. The c e l l s were f i l l e d with 0.5 mol/L CaCl- s o l u t i o n and s t i r r e d continuously f o r 72 h t o d i s p l a c e exchangeable r a d i o n u c l i d e s . A f t e r a r i n s e with demineralized water to remove r e s i d u a l C a C l s o l u t i o n , the c e l l s were f i l l e d with KTOX s o l u t i o n and s t i r r e d f o r 24 h t o remove r a d i o n u c l i d e s a s s o c i a t e d with oxyhydroxides. A l l s o l u t i o n s were analyzed by gamma spectrometry t o determine the amounts of r a d i o n u c l i d e s e x t r a c t e d . Residual a c t i v i t y was measured by d i r e c t gamma counting of the c e l l s . 9

Results E x t r a c t i o n of I n a c t i v e Coupons with KTOX S o l u t i o n . Average i r o n e x t r a c t i o n rates are p l o t t e d as a f u n c t i o n o f cumulative e x t r a c t ion time i n Figure 2. Where r a t e s f o r the a l t e r e d and unaltered g r a n i t e d i f f e r , the confidence l e v e l a t which the d i f f e r e n c e i s s i g n i f i c a n t i s i n d i c a t e d i n brackets. During the f i r s t s i x hours of e x t r a c t i o n , more i r o n i s r e moved from the a l t e r e d g r a n i t e than from the f r e s h g r a n i t e . The extra i r o n from the a l t e r e d g r a n i t e i s b e l i e v e d t o be that associ a t e d with the production o f i r o n oxyhydroxides during the 101-d exposure of the g r a n i t e to GGW. The i r o n e x t r a c t i o n r a t e s f o r both f r e s h and a l t e r e d g r a n i t e decrease f o r the f i r s t 24 h and become the same constant r a t e f o r the remaining 24 t o 120 h . Thus the i r o n a s s o c i a t e d with oxyhydroxides (formed during recent exposure to GGW or during hydrothermal a l t e r a t i o n ) i s removed during the f i r s t 24-h exposure to

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

Figure 1.

C r o s s - s e c t i o n a l view of c y l i n d r i c a l m i x i n g - c e l l .

2 7 (90%) Ε 6

I

I FRESH GRANITE

HI GRANITE ALTERED 101 d IN GRANITE GROUNDWATER

^ 5 (95%)

< cr

4

( ) CONFIDENCE LEVEL OXYHYDROXIDES FORMED DURING 101 d "EXPOSURE TO GRANITE GROUNDWATER

3

cr hx

IRON OXYHYDROXIDES

LU

-z. Ο cr

2 3 4 5 6 12 24 48 72 120 CUMULATIVE EXPOSURE TIME (h) TO KTOX

F i g u r e 2. Average i r o n e x t r a c t i o n rates f o r f r e s h and a l t e r e d Lac Du Bonnet g r a n i t e as a f u n c t i o n of cumulative e x t r a c t i o n time.

3.

WALTON ET AL.

Radionuclide Sorption Mechanisms and Rates

53

KTOX. Iron extracted during the subsequent 24 to 120 h i s probably a s s o c i a t e d with the i r o n - b e a r i n g minerals (e.g. magnetite). This hypothesis i s c o n s i s t e n t with autoradiographic s t u d i e s des c r i b e d i n the f o l l o w i n g s e c t i o n . S e l e c t i v e Chemical E x t r a c t i o n of A c t i v e Coupons. Using gamma spectrometric a n a l y s i s of the groundwaters i n the s o r p t i o n and desorption steps, d i s t r i b u t i g n coe||^cienÇj^(k )ytjave f f f c a l c u l a t e d f o r the isotopes Co, Cs, Cef Se, Sb and Sn. Values of k f o r these isotopes i n GGW and b r i n e have been reported elsewhere ( 2 ) . Figure 3(A) shows a photograph of a t y p i c a l g r a n i t e coupon that was exposed to the GGW s o l u t i o n . Autoradiographs of t h i s coupon a f t e r a 28-d GGW d e s o r p t i o n , a 72-h C a C U e x t r a c t i o n and a 24-h KTOX e x t r a c t i o n ( F i g u r e s 3(B), (C) and (D)) i n d i c a t e that the areas of most h i g h l y concentrated a c t i v i t y ( l i g h t areas i n the autoradiographs) correspond to ferromagnesian and/or other dark, i r o n - b e a r i n g minerals i n the photograph. However, Figure 3(B) shows that there i s some s o r p t i o n on a l l mineral phases. F i g u r e 3(C) shows a darkening of a l l areas a f t e r CaCl^ e x t r a c t i o n , i n d i c a t i n g the removal of exchangeable a c t i v i t y from a l l areas. Figure 3(D), taken a f t e r the 24-h KTOX e x t r a c t i o n , shows a decrease i n a c t i v i t y i n the l o c a t ion of the i r o n - b e a r i n g minerals and v i r t u a l e l i m i n a t i o n of a c t i v i t y i n a l l other areas. I t i s not p o s s i b l e to d i s c e r n the behaviour of any i n d i v i d u a l n u g l i d e ^ y o m t^g^e auj^radio^çaphs; £j>yever, sgççific studies of Sr, Cs, Ce, Pu, Se, Pm and Am, using a combination of autoradiographic and pétrographie techniques, i n d i c a t e a c l e a r preference f o r s o r p t i o n on ferromagnesians, opaques and t h e i r a l t e r a t i o n products (4,5). The amount of r a d i o n u c l i d e removed from the g r a n i t e i n the groundwater desorption and s e l e c t i v e e x t r a c t i o n procedures wgg measured,by gammayspectrometry. The data i s summarized f o r Co, Cs, Ce and Se i n Figure 4. In t h i s f i g u r e the percentage of the i n i t i a l r a d i o n u c l i d e inventory sorbed during contact with the two groundwaters i s i n d i c a t e d n u m e r i c a l l y . In the bar chart the t o t a l amount of sorbed a c t i v i t y has been normalized i n order to compare the r e l a t i v e amounts of s o r b e ^ 2 § y^Ç ^ by the d i f f e r e n t reagents. A c t i v i t i e s f o r Sb and Sn were below background d e t e c t i o n l i m i t s . The a c t i v i t y on the surface of the g r a n i t e a f t e r the 28-d s o r p t i o n has been d i v i d e d i n t o four c a t e g o r i e s : exchangeable, a s s o c i a t e d with oxyhydroxides, associ a t e d with hydrated s i l i c a t e s , and " f i x e d " to ferromagnesians, t h e i r a l t e r a t i o n products and/or other opaque mineral phases. There are three s i g n i f i c a n t features i n Figure 4. F i r s t , the various s o r p t i o n mechanisms a f f e c t each n u c l i d e d i f f e r e n t l y . Second, the amount of each r a d i o n u c l i d e that i s exchangeable or r e v e r s i b l y sorbed i s l e s s than 50% f o r a l l n u c l i d e s t e s t e d . In 28 days, more than 50% of the sorbed r a d i o n u c l i d e s have undergone phase transformation or reacted with oxyhydroxides to form nonexchangeable phases. T h i r d , f o r a given r a d i o n u c l i d e , the n

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

a

c t i v i t

x t r a c t e
Μ ιΗ

Φ

Ο

αΙ δ Φ c ο

•ρ to 3

U

•H Ρ Cd Pu f-l CM Pu Pu h J Q

3.

Radionuclide Sorption Mechanisms and Rates

WALTON ET AL. G S -

57

Granite Groundwater Saline Groundwater

Groundwater

G

% Sorbed

59 9

S

2 8 - day Desorption 43

81 4 8

CaCL

55 18 I

100

1

80

I

First 2 4 - h Hot N a C 0 2

Exchangeable

KTOX-Oxyhydroxides

3

-

Hydrated Silicates

Second 4 8 - h K T O X 60

h

"Fixed"

Residual

i Is*

40

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

20

0 60,

137,

Co

Cs

144,

75

Ce

Se

F i g u r e 4. Percentage of sorbed r a d i o n u c l i d e s as a f u n c t i o n of v a r i o u s s o r p t i o n mechanisms f o r 28-cli contact with 60ç _ 1 3 7 _ , 144 e- and ^Se-doped g r a n i t e and s a l i n e groundwaters. o

Cs

C

χ

6 0

CO

ο

EXPERIMENTAL DATA NO SORPTION LINE

rr

SINGLE FIRST ORDER MODEL

LJJ

ο ζ ο ο

DOUBLE FIRST ORDER MODEL

Lu > Lu

5

10

15

20

25

RELATIVE TIME (CELL VOLUMES) F i g u r e 5. Comparison of s i n g l e f i r s t - o r d e r and f i r s t - o r d e r models to 6 0 ç m i x i n g - c e l l data. o

double

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

58

Table V.

Double F i r s t - O r d e r Model Parameters and F i t Variance

Isotope Reference Variance

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch003

60

Co

137

Cs

144 Ce

75

Se

Rate Constants χ 10

3 37 34 33 4 35

0.010 0.010 0.025 0.056 0.020 0.007

η «cm 21.0 1.87 3.59 265. 3.27 0.500

6.96 11.6 5.52 33.2 9.87 7.17

η «cm 17.0 1.61 17.2 67.6 2.19 0.763

0.374 1.67 3.11 0.189 0.496 0.629

3 37 34 33 4 35

0.016 0.020 0.004 0.007 0.006 0.013

3.35 17.2 6.86 2.90 0.622 0.482

9.97 33.2 17.0 16.6 9.69 10.0

2.34 2.08 1.27 0.952 0.213 0.102

0.687 2.48 2.07 2.09 0.300 1.75

3 37 34 33 4 35

0.037 0.050 0.069 0.218 0.034 0.017

3 37 34 33 4 35

0.036 0.034 0.046 0.069 0.019 0.030

113. 1130. 6.19 227. 25.1 2.31 1.72 1.90 1.20 0.602 0.518 0.856

9.28 58.8 3.09 142. 9.20 9.89 13.8 15.6 10.1 9.73 8.59 13.2

83.1 46.9 12-8 30.1 17.0 1.18 0.447 0.703 0.887 1.66 0.789 0.994

0.475 0.211 0.054 0.671 0.225 1.36 0.383 1.19 0.487 0.225 0.158 0.309

3.

Radionuclide

WALTON ET AL.

Sorption

Mechanisms

and

Rates

59

e q u i l i b r i u m d i s t r i b u t i o n c o e f f i c i e n t s ( k ) which can be c a l c u l a t ed by assuming dS^/dt and dS2/dt are zero i n Equation 4 as time becomes l a r g e * k

k

al " a2

=

( S

( S

1

2

/ C )

/ C )

=

α) > >

cfl

Ή ί-,

>>> N i ( C Q ) 3

I

I

I

-0.5

-0.4

-0.3 Eh

2

2

I

I

0.2

-0.1

I 0

(V)

Figure 2. Solubility of Nickel as a Function of E h at 25°C. The horizontal lines i n the lower part of the figure show the range of dominance of solids controlling solubility and aqueous species as functions of E h . Figures 3 through 7 are interpreted similarly. See text for further explanation.)

Figure 3. Solubility of Selenium as a Function of E h at 25°C.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch009

9.

EARLY ET A L .

Geochemical Controls on Radionuclide Releases

Figure 4. Solubility of Tin as a Function of Eh at 25°C. [Sulfur speciation has only a minor effect on tin solubility (not shown in the figure) for Eh 10

^10-6

b

6a

7a

>10'

Solubility estimates from experiments and natural waters (mol/L)

Geochemical Controls on Radionuclide Releases

9. EARLY ET A L .

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch009

ο ι-*

S ®

v|

Λ| ^

S S 3 22X

X ο*

X χ x σο co *»

2 X

ô

x

X

X 00

2 < = > 2 < = > X

1.0*> 1.56 1.13 6.49 1.97 8.48

1

w xlO * ( e q / g )

2.16 0.34 1.36 0.51 2.20

+ ± ± + +

a

j

0.82 0.71 1.06 1.00 0.99

0.40 0.02 0.23 0.01 0.18

± + + + ±

log 3

0.15 0.04 0.18 0.01 0.08

there i s a d i f f e r e n c e of ~8% i n the u n i t c e l l volumes of the two s t r u c t u r e s . This observation may have s i g n i f i c a n c e to the problem of accommodation of a range of ions of d i f f e r e n t s i z e s i n t o a nuclear waste i s o l a t i o n host. It i s l i k e l y that t r a n s u r a n i c ions w i l l be incorporated i n t o such materials i n the t e t r a v a l e n t form. Given the tabulated r a d i i of the t e t r a v a l e n t t r a n s u r a n i c ions (2), which are smaller than l r , s u b s t i t u t i o n of these ions by appropriate valence compensation with a d i v a l e n t i o n would y i e l d a composite A i o n small enough to p o s s i b l y s t a b i l i z e the Z i r c o n s t r u c t u r e as opposed to the Monazite s t r u c t u r e i n the A P O 4 s e r i e s (Figure 1). A r e c o n s t r u c t i v e transformation i n v o l v i n g a s i g n i f i c a n t volume change such as t h i s could have a severe i n f l u e n c e on s t r u c t u r a l i n t e g r i t y . In summary, we have demonstrated that the concept of a s t r u c t u r e - f i e l d map i s a u s e f u l one i n systematizing the occur­ rence of c r y s t a l s t r u c t u r e s i n a s e r i e s of i s o - s t o i c h i o m e t r i c compounds. In a d d i t i o n , the concept of a weighted mean radius of an i o n at a p a r t i c u l a r s i t e i n a s u b s t i t u t e d compound has been found to be a v a l i d one. The use of a SFM to p r e d i c t s t r u c t u r a l s t a b i l i t y and provide warnings about p o s s i b l e p o l y ­ morphism (and so s t r u c t u r a l i n t e g r i t y ) i n a complex multicomponent s u b s t i t u t e d system could be a u s e f u l t o o l i n a s s e s s i n g p o t e n t i a l hosts f o r nuclear waste i s o l a t i o n . 1

3

1

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch018

fi

3

+

v

3

p

314

G E O C H E M I C A L BEHAVIOR

Table 1.

WASTE

Results of L i n e a r Least-square f i t s t o V l / 3 = Β + Cx f o r AP- V 0 4 Compounds X

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch018

O F RADIOACTIVE

X

A_

Structure

X

La Ce Pr

Monazite tl

0-1.0 0-0.78 0-0.44

Pr Nd Sm Eu Gd Ho Yb

Zircon

M

it II

π It II tl

0.95-1.0 0,88-1.0 0.765-1.0 0.61-1.0 0.30-1.0 0-1.0 0-1.0

4

C

C/A -r

B

0.191(1) 0.193(2) 0.181(4)

1.03(1) 1.04(1) 0.98(2)

M).2 ^0.24 0.249(5) 0.234(6) 0.247(2) 0.244(1) 0.244(1)

vL.l

D

H

In p r a c t i c e Djg >> D H , (10) and c o u n t e r d i f f u s i o n i s c o n t r o l l e d by the slower hydronium i o n . This suggests assuming t h a t :

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch022

a

which l i n e a r i z e s the system of Equations (12)-(14). Assuming f u r t h e r chemical e q u i l i b r i u m between sodium species on the g l a s s s u r f a c e and sodium species immediately adjacent i n the bulk phase, the law of mass a c t i o n r e q u i r e s t h a t : =K

n(t)

t>0 —

(16)

where Κ i s a true e q u i l i b r i u m constant. W i t h i n the context of the above approximations, the o r i g i n a l system of Equations (12)-(14) can be solved w i t h the u s u a l boun­ dary and i n i t i a l c o n d i t i o n s : C(«,t) - C C(x,0) = C n(0) C

s o l

=

(0)

C

(17)

Q

(18)

Q

/ K

(19)

= 0

(20)

Q

The p r e d i c t e d asymptotic behaviors f o r the leach r a t e are follows: (4,11)

L.(t)

- Οο,β H-nt

.

Î 2 Κ

2

k +

D

3

2

_

(k 3)

t 2

t

l a r

*

e

e n o U

*

h

as

( 2 1 )

Φ = 0

and Loo(t) - co * / ^ H

t l a r g e enough Φ + 0

(22)

354

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

Equations (21) and (22) both suggest that l e a c h i n g w i l l e v e n t u a l l y slow down t o zero under s e l e c t i v e leaching c o n t r o l . Under the c o n d i t i o n s of Equation (21), l e a c h i n g tends t o zero as a build-up of g l a s s m o d i f i e r s i n s o l u t i o n allows the s o l i d s u r f a c e t o come to e q u i l i b r i u m with the leachant. Under the c o n d i t i o n s of Equation (22), species build-up e f f e c t s do not p l a y a r o l e , r e g a r d l e s s of how s m a l l the flow r a t e , and l e a c h i n g tends t o zero as the g l a s s matrix gets depleted of network m o d i f i e r s . This accords w i t h p h y s i c a l i n t u i t i o n . Equation (22) i s the c l a s s i c a l expression f o r the leach r a t e per u n i t area under d i f f u s i o n c o n t r o l l e d c o n d i t i o n s .

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch022

The General Case While i t proved convenient to consider flow r a t e e f f e c t s on l e a c h i n g under network d i s s o l u t i o n c o n t r o l and s e l e c t i v e l e a c h i n g c o n t r o l s e p a r a t e l y f o r i l l u s t r a t i o n purposes, these mechanisms are not independent of each other. Indeed, as i o n exchange r e a c t i o n s of the kind (10) deplete the s o l u t i o n of hydronium i o n s , the s o l u t i o n becomes more a l k a l i n e causing o r t h o s i l i c i c a c i d to i o n i z e and, consequently, a d d i t i o n a l d i s s o l u t i o n of the g l a s s matrix according to r e a c t i o n s of the kind (1). I t i s , however, the flow c o n d i t i o n of the s o l u t i o n that determines the long-term r a t e - c o n t r o l l i n g l e a c h i n g mechanisms. I f the s o l u t i o n i s stagnant, s a t u r a t i o n of the s o l u t i o n i s reached much sooner with respect to the network formers than the a l k a l i s ; thus l e a c h i n g w i l l e v e n t u a l l y take place a t a r a t e c o n t r o l l e d by s e l e c t i v e l e a c h i n g o f the a l k a l i s . I f the s o l u t i o n i s flowing, s a t u r a t i o n i s never achieved, and s e l e c t i v e l e a c h i n g , a process which otherwise would slow down to zero, i s c o n t r o l l e d e v e n t u a l l y by the constant network d i s s o l u t i o n r a t e of the g l a s s matrix. In t h i s case, a l l elements e v e n t u a l l y leach out a t the same r a t e d i c t a t e d by the d i s s o l u t i o n k i n e t i c s of the network forming element with highest s o l u b i l i t y i n s o l u t i o n and by the flow c o n d i t i o n s of the s o l u t i o n . This can be i l l u s t r a t e d f o r the case of sodium and s i l i c o n l e a c h i n g from nuclear waste glasses by combining together to the modeling approach o u t l i n e d e a r l i e r f o r network d i s s o l u t i o n and s e l e c t i v e l e a c h i n g c o n t r o l s , and by t a k i n g i n t o account the d i s s o c i a t i o n of the o r t h o s i l i c i c a c i d , Reaction (2), and the a u t o p r o t o l y s i s of water: H 0^±OH" + H 2

+

(23)

The mathematical formulation of the model complicates somewhat (4), and i t i s not reported here f o r the sake of s i m p l i c i t y . In p a r t i c u l a r , the model r e s u l t s i n a system of coupled, nonl i n e a r ordinary and p a r t i a l d i f f e r e n t i a l equations which have been f u l l y implemented i n a computer code, named LIX, t o p r e d i c t elemental r e l e a s e s of s i l i c o n and sodium from b o r o s i l i c a t e glass.

22.

Effects

PESCATORE A N D MACHIELS

of

Water

Flow

Rates

on Leaching

355

Figure 2 shows the p r e d i c t e d , normalized cumulative mass l o s s e s based on the behaviors o f s i l i c o n and sodium f o r three d i f f e r e n t values of the leachant renewal frequency. The p h y s i c a l parameters used r e f e r t o the l e a c h i n g of PNL 76-68 b o r o s i l i c a t e g l a s s i n d e i o n i z e d water a t 90°C, (4) and r e f e r e n c e i s made t o the geometric s u r f a c e area, SA, of the sample. In p a r t i c u l a r , the curves corresponding t o s i l i c o n and sodium tend t o have the same, constant slope with i n c r e a s i n g flow r a t e . In p a r t i c u l a r , the curves corresponding t o Φ = 1 day" p r a c t i c a l l y coincide, i n d i c a ­ t i v e o f network d i s s o l u t i o n c o n t r o l .

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch022

1

Figure 3 shows the p r e d i c t e d behavior of the pH of the s o l u ­ t i o n as a f u n c t i o n of leachant renewal frequency f o r the same system parameters. As can be seen, the higher the flow r a t e , the sooner steady s t a t e i s achieved, and the c l o s e r the leachant composition t o that of the o r i g i n a l s o l u t i o n . In p a r t i c u l a r , the pH curve f o r the s t a t i c case (Φ= 0) shows that the s o l u t i o n pH has not reached steady s t a t e yet a f t e r 28-days l e a c h i n g . Approach to steady s t a t e under the s t a t i c l e a c h i n g c o n d i t i o n s can be a very lengthy process. However, an e q u i l i b r i u m pH value can be estimated by use of the s o l u t i o n e l e c t r o n e u t r a l i t y c o n d i t i o n as a p p l i e d t o the r e a c t i o n s modeled. Indeed, a t a l l times: +

+

[H ]

+

+ [Na ] +

I [H ]

- [0H ] +

+ [Na ]

- [H Si0 -] =

- [0H~]

3

4

_

- [H Si0 ] } 3

4

t

=

Q

(24)

which y i e l d s an e q u i l i b r i u m pH of -12 a t 90°C based on the e q u i l i b r i u m r e l a t i o n between sodium s o l u t i o n and s u r f a c e s p e c i e s : k+C

iFi and

( 2 5 )

on values o f the p h y s i c a l parameters from Reference 4. Figure 4 shows a p l o t of the long term, normalized l e a c h r a t e , L * ( t ) = L o o ( t ) / L s i ( t = 0 ) , based on the behaviors of sodium and s i l i c o n as a f u n c t i o n of Φ, where l e a c h i n g f o l l o w s a law of the type (21). T h i s lower range of Φ values may encompass flow r a t e s i n a nuclear waste r e p o s i t o r y under normal o p e r a t i o n a l conditions. Network d i s s o l u t i o n c o n t r o l operates i n the higher ranges o f Φ according to a law of the type (8). Higher ranges of Φ values may encompass flow r a t e s i n a nuclear waste r e p o s i t o r y under accident c o n d i t i o n s . I f species are r e l e a s e d , whose s a t u r a t i o n c o n c e n t r a t i o n i s lower than the o r t h o s i l i c i c a c i d s a t u r a t i o n c o n c e n t r a t i o n , new s o l i d phases may form both i n s o l u t i o n and a t the s o l u t i o n - g l a s s i n t e r f a c e (12). Formation of new phases i n s o l u t i o n may a c c e l e r a t e l e a c h i n g ; new phases a t the s o l u t i o n - g l a s s i n t e r f a c e may s t a b i l i z e the d e a l k a l i z e d l a y e r and slow down both l e a c h i n g mechanisms.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch022

356

Figure 1.

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

G r a p h i c a l Representation of the Waste Form-Leachant System.

DAYS

Figure 2.

P r e d i c t e d , Normalized Mass Loss v s . Time f o r Various Values of Φ. [φ] = [ d a y " ] ; Q* - grams of Glass Leached A f t e r 28 Days Assuming Congruent D i s s o l u t i o n at the I n i t i a l S i l i c o n Leach Rate. 1

22.

Effects

PESCATORE A N D MACHIELS

1

of

Water

Flow

1

_ SA/V= 10, m T = 90 °C

Rates

on Leaching

357

1

_l

1

φ = 0 day" —

—

^

s s s s s

—•

0.1

pH 8

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch022

-

10

-

-

1

0

Figure 3.

1

7

14 DAYS

21

28

P r e d i c t e d Behavior of S o l u t i o n pH v s . Time f o r Various Values of Φ.

I0
» . ι 30

40

50

60

70

80

90

100

TIME, days

FIGURE 4.

S t a t i c Leach Test of Hg(10 ) -Cement 3

2

24.

SCHEELE ET AL.

Leach Resistance of Iodine Compounds

383

in seawater which exhibits a much higher leach rate than in other waters. No explanation has been determined for the l a t t e r result which i s in contrast to that found by Morgan et a l . (22) for Ba(I0 )2. Figure 2 also shows the dynamic leach results for Ba(103)2 Comparison of the dynamic leach test results shown in Figures 2 and 4 shows Ca(I03) to behave similarly to Ba(I0 )2. Note also that the fraction leached i s a factor of 10 greater than in the s t a t i c t e s t s . From the dynamic test results in Figure 2, using a linear extrapolation of the 40 to 70 day data, 5 years would be required to leach 1% of the iodine from a 208 L monolith. This estimated leach rate i s comparable (factor of 3 less) to that found for 9 wt% iodine as Ba(I0o)o by Clark 3

i

n

c e m e n t

2

3

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch024

(20).

In s o l u b i l i t y tests of the pure compounds in d i s t i l l e d and cement-equilibrated water, iodate concentrations in both liquids were near the expected theoretical values for Ba(I0o) and Ca(I0 )2. For Hg(I0 )2 the concentration in d i s t i l l e d water corresponded to the expected value; however, the concentration in the cement-water was a factor of -1000 higher. This higher concentration was attributed to hydrolysis due to the high pH (-12) of the cement-water. Hydrolysis would account for the release of iodine from the HgHOoK-cement. The iodate concentrations found in the leachates of the cements containing Ba(I0o) and Ca(I03) were a factor of 10 lower than expected. No metallic ion concentration was s u f f i c i e n t l y high to cause precipitation of the iodate. In the s t a t i c leach test of AgZI in cement, presented in Figure 5, iodine leached from the AgZI cement at nearly the same rate as from the iodate cements. In the dynamic leach t e s t , also presented in Figure 5, the leach rate was a factor of 10 faster than from Agi cement, and a factor of 10 slower than from Ba(I03)2 cement. Based on dynamic leach test sample 1 in Figure 5, 100 years would be required to leach 1% of the iodine from a 208 L cement monolith. The iodine release rate from AgZI may depend on the iodine loading of the AgZ since a fraction of the iodine i s apparently held as a less stable molecular complex with t h i s fraction increasing with increasing iodine loading (2). In contrast, iodine i s readily lost from PbXI-cement (see Figure 6). When the concrete was prepared, the cement mixture turned purple suggesting release of elemental iodine, which in the alkaline environment of the cement, disproportionates to iodide and iodate. 2

3

3

2

2

Conclusion Our studies have shown that there i s a considerable difference in s t a b i l i t y and leach resistance among the various iodine compounds in Portland III cement. Of the compounds examined, Agi had the best leach resistance followed by AgZI, Ba( 103)2, ^ ( ^ 3 ) 2 »

384

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

10

2

DISTILLED WATER (STATIC)

ζ υ < 10

3

ο ο ο 10^

-

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch024

< oc Ο

ζ 10

5

20

FIGURE 5·

40 TIME, days

60

80

S t a t i c and Dynamic Leach Tests of AgZI-Cement

10° DISTILLED WATER LEACHATE

SAMPLE #1 Ο

< ζ û ο

1

ίο

1

Ι­ Ο

έ α. Ο LU Ν —1

< 2 oc Ο Ζ 10

2

ΙΟ

_L

.χ-

20

30

40

50

TIME, days

FIGURE 6.

S t a t i c Leach Test of ~370 mgl/g PbX i n Cement

24.

Leach Resistance of Iodine Compounds

SCHEELE ET AL.

385

Η 9 ( Ι 0 3 ) , and S r ( I 0 ) 2 . Long time extrapolations of leach rates are uncertain to one or two orders of magnitude, but the data indicate that i f the disposal form comes in continuous contact with the water the I w i l l be released before i t has decayed. Thus, good disposal strategy includes a mechanism for dispersal such that d i l u t i o n to harmless levels i s achieved. For interim storage, where a dry environment can be assured, and for transportation, the forms appear to be adequate. 2

3

1Z9

Literature Cited

1.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch024

2.

3.

4.

5.

6.

Russell, J. L.;Hahn, P. B. "Public Health Aspects of Iodine129 from the Nuclear Power Industry." Radiol. Health Data Rep. 12:189, 1971. Burger, L. L.; Scheele, R. D. "Iodine Fixation Studies at the Pacific Northwest Laboratory." In Management Modes for Iodine-129, W. Hebel and G. Cottone, eds. Harwood Academic Publishers, New York, 1982. Burger, L. L.; Scheele, R. D.; Wiemers, K. D. Selection of a Form for Fixation of Iodine-129. PNL-4045, Pacific Northwest Laboratory, Richland, Washington, 1982. Holladay, D. W. A Literature Survey: Methods for the Removal of Iodine Species from Off-Gases and Liquid Waste Streams of Nuclear Power and Fuel Reprocessing Plants with Emphasis on Solid Sorbents. ORNL/TM-6350, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1979. Jubin, R. T. A Literature Survey of Methods to Remove iodine from Off-Gas Streams Using Solid Sorbents. ORNL/TM-6607, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1979. Burger, L. L.; Burns, R. E. Technical Requirements for the Control of I in a Nuclear Fuels Reprocessing Plant, PNL3186, Pacific Northwest Laboratory, Richland, Washington, 1979. IAEA. Radioiodine Removal in Nuclear Facilities. IAEA Technical Reports Series 201, International Atomic Energy Agency, Vienna, 1980. McKay, H. A. C.; Miquel, P.; White, I. F. "Management Modes for Iodine-129." In Management Modes for Iodine-129, W. Hebel and G. Cottone, eds. Harwood Academic Publishers, New York, 1982. Burns, R. E.; Defield, J. G. Disposal of Radioactive Iodine in Space. NASA Technical Paper 1313, Marshall Space Flight Center, Alabama, 1978. Burger, L. L. Determining Criteria for the Disposal of Iodine-129, PNL-3496, Pacific Northwest Laboratory, Richland, Washington, 1980. Allard, B.; Torstenfeld, B.; Andersson, K.; Rydberg, J. "Possible Retention of Iodine in the Ground." In Scientific Basis for Nuclear Waste Management, Vol. 2, p. 673, C. J. M. Northrup, ed., Plenum Press, New York, 1980. 129

7.

8.

9. 10.

11.

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

386

12.

13.

14.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch024

15.

Fried, S.; Friedman, A. M.; Cohen, D.; Hines, J. J.; Strickert, R. G. The Migration of Long-Lived Radioactive Processing Wastes in Selected Rocks. Ann. Rpt. Project AN0115A, FY 1977, ANL-78-46, Argonne National Laboratory, Argonne, Illinois, 1978. Winters, W. I. The Effects of Hot-Pressing Conditions on the Properties of Iodine Sodalite. RHO-LD-153, Rockwell Hanford Operations, Richland, Washington, 1980. Strachan, D. M.; Babab, H. Iodide and Iodate Sodalites for the Long-Term Storage of Iodine-129. RHO-SA-83, Rockwell Hanford Operations, Richland, Washington, 1979. Malagani, J. P.; Wasniewski, Α.; Doreau, M.; Robert, G.; Mercier, R. "Conductivite Electrique et Spectre de Diffusion Raman des Verres Mixtes AgPO -MI avec M = Cd, Hg, Pb. Correlation entre Conductivite et Structure." Mat. Res. Bull. 13:1009, 1978. Dean, J. A. Lange's Handbook of Chemistry. Eleventh Ed., McGraw-Hill Book Company, New York, New York, 1973. Horner, D. E.; Mailen, J. C.; Bigelow, H. R. "Solubility of PdI in Nitrate and Perchlorate Solutions.", CONF-761002-4, pp. 1-24, 1973. Sidell, A. Solubilities of Inorganic and Metal Organic Compounds, Vol. 1. Third edition. D. Van Nostrand Company, Inc., New York, New York, 1953. Duval, C. Inorganic Thermogravimetric Analysis. Trans. R. E. Oesper. Elsevier Publishing company, New York, 1963. Clark, W. E. "The Isolation of Radioiodine with Portland Cement. Part 1: Scoping Leach Studies," Nuc. Tech. 36:215221, 1977. Morgan, M. T.; Moore, J. G.; Devaney, H. E.; Rogers, Williams, C.; Newman, E. "The Disposal of I-129." Paper presented at the Symposium on Science Underlying Radioactive Waste Management, November 28 - December 1, 1978, Boston, Massachusetts, 1978. Partridge, J. A; Bosuego, G. P. Waste Management of Mercuric Nitrate Off-Gas Scrubber Solution. A Laboratory Study. HEDL-TME 79-11, Hanford Engineering Development Laboratory, Richland, Washington, 1979. Wiemers, K. D. "Carbon-14 and Iodine-129 Fixation." Nuclear Waste Management Quarterly Progress Report October through December 1977. Eds. A. M. Platt, J. A. Powell. PNL-2377-4, Pacific Northwest Laboratory, Richland, Washington, 1978. Wiemers, K. D. "Carbon-14 and Iodine-129 Fixation." Nuclear Waste Management Quarterly Progress Report January through March 1978. Eds. A. M. Platt , J. A. Powell. PNL-2378-1, Pacific Northwest Laboratory, Richland, Washington, 1978. Wiemers, K. D. "Carbon-14 and Iodine-129 Fixation." Nuclear Waste Management Quarterly Progress Report January through March 1979. Eds. A. M. Platt, J. A. Powell. PNL-3000-1, Pacific Northwest Laboratory, Richland, Washington., 1979. 3

16. 17.

2

18. 19. 20.

21.

22.

23.

24.

25.

3

24. 26.

27.

28.

SCHEELE ET AL.

387

Wiemers, K. D. "Carbon-14 and Iodine-129 Fixation." Nuclear Waste Management Quarterly Progress Report April through June 1979. Eds. A. M. Platt, J. A. Powell. PNL-3000-2, Pacific Northwest Laboratory, Richland, Washington, 1979. Wiemers, K. D. "Carbon-14 and Iodine-129 Fixation." Nuclear Waste Management Quarterly Progress Report July through September 1979. Eds. A. M. Platt, J. A. Powell. PNL-3000-3, Pacific Northwest Laboratory, Richland, Washington, 1979. Altomare, P. M.; Barbier, M.; Lord, Ν.; Nainan, D. Assessment of Waste Management of Volatile Radionuclides. PB80-147754. The Mitre Corporation, McLean, VA, 1979.

RECEIVED

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch024

Leach Resistance of Iodine Compounds

November 3, 1983

25 Nuclear Waste—A View from Washington, D.C. MIKE MCCORMACK

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

McCormack Associates, Inc., 508 A Street, SE, Washington, DC 20003

If the American people were aware of the tremendous amount of scientific research--to say nothing of the outstanding quality of engineering development--that has gone into management policies and regulations for handling, transporting, and storing high-level and low-level radioactive waste, much of the emotionalism and fear associated with this subject would be eliminated. It should be observed at this point that one of the responsibilities that falls on the shoulders of all scientists in this country is the scientists' obligation to help their fellow citizens, who have not had the advantage of technical or scientific training, to understand the realities of such subjects as nuclear waste, thus making it possible to legislate more intelligently and realistically in subject areas wherein technical and scientific facts are so important. Last December the Congress enacted landmark legislation entitled, "The Nuclear Waste Policy Act of 1982." It establishes a number of federal programs for the management and storage of high-level nuclear waste and spent nuclear fuel. The U.S. Department of Energy (DOE) is presently developing programs for implementing that law. At the same time, the various state legislatures are preparing interstate compacts and submitting them to the Congress for approval, as called for in the Low-Level Radioactive Waste Policy Act of 1980. In addition, the new budget requests for FY 84 for nuclear waste research and development are now under consideration by the Congress. Before reviewing these subjects in greater detail, it may be in order to call to mind several facts about nuclear waste that must be understood before any rational consideration of laws, programs, regulations, or research can proceed. 1. The first fact is that there are no scientific, technical, or economic obstacles that delay—let alone prevent—the safe handling of all nuclear wastes. A number of completely acceptable methods exist today for the removal of all highlevel wastes from the biosphere, essentially forever, and certainly far beyond the time when they will have decayed away to activity levels below the natural uranium from which they came. 0097-6156/ 84/ 0246-0391 $06.00/ 0 © 1984 American Chemical Society

392

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

For chemists who are accustomed to severe peer review, the words "all" and "forever" have a slightly different meaning than they do for the average non-technical person. It is important that scientists recognize the discontinuity that exists between their professional language and the language of the average citizen. In the real world, it is an accurate statement of fact that the technology exists to totally remove all high-level nuclear waste from the biosphere, essentially forever; that inexpensive and simple technologies do exist to accomplish this. It is necessary to help others outside the scientific community to understand this fact. 2. The second fact is that there are a number of satisfactory methods for solidifying high- or low-level nuclear wastes for permanent disposal. One system or another may be preferred for a specific situation, and there will undoubtedly be several schools of thought as to which one is best in each case. 3. The third fact is that spent nuclear fuel is not waste. Spent nuclear fuel contains 2% to 3% waste, but is about 97% recoverable uranium and plutonium. Each bundle has the potential electric energy equivalent of more than 10 million barrels of oil. High-level nuclear wastes consist of fission products and actinides that are extracted from spent fuel, but not saved for commercial use or research. Spent fuel may be temporarily stored until it is reprocessed to separate the waste from the valuable plutonium and uranium. The remaining glassified waste will then be permanently entombed. 4. The fourth fact is that there will be no high-level waste extracted from spent commercial nuclear fuel until there is a reprocessing program with a chemical separation facility to isolate the waste from the reuseable fuel. Since this will not be accomplished during this decade, there will not be any high-level waste available from commercial nuclear fuel for geologic storage before 1990. 5. The fifth fact is that the most dangerous ingredients of high-level waste do not (contrary to some popular misconceptions) last for geologic periods of time. Highly active radio-isotopes cannot be long-lived. This is a contradiction in terms. The activity level of the most radioactive isotopes in waste, such as cesium-137 and strontium-90, decay in 1,000 yr by a factor of 10 billion, and glassified waste of that age would be scarcely more hazardous than the natural uranium ore mined today in the Western United States.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

25. M C C O R M A C K

A View from Washington, D.C.

393

6. The sixth fact is that extremely demanding and rigid regulations, supported by exhaustive research and the highest standards of engineering, have been established for the management, transportation, and storage of all radioactive wastes-from the least dangerous low-level wastes originating in hospitals and research laboratories to the most dangerous high-level wastes from spent nuclear fuel. Strict compliance with every detail of every regulation reduces the threat to the environment or to public health and safety to a level substantially below that from any one of a multitude of non-nuclear sources. Accordingly, all such regulations must be observed religiously, thus insuring that any threat to the environment or to human health and safety shall continue to decline to levels below its present low level, even as the people of this country and the world depend more and more on nuclear medicine, research, industrial applications, and power production. Another piece of legislation, The Low-Level Radioactive Waste Policy Act of 1980, establishes the policy that each state is responsible for disposal of the commercial low-level waste generated within its borders and that such waste can be most safely and efficiently managed on a regional basis. The law encourages states to enter into interstate compacts to establish and operate regional disposal facilities for low-level waste. This law requires subsequent approval of the compacts by the Congress. Perhaps the most significant provision of the act was the authority given to Congressionally approved, compact states to exclude waste generated outside their compact region after January 1,1986. Today, individual states with waste Sites cannot refuse waste without being in violation of the commerce clause. Thus, the right of a region with an operating compact to refuse to accept waste from an outside state provides an incentive for the states of each region to form a compact and select a site within their region to store low-level waste. Furthermore, a state that refuses to join a compact will be obligated, starting in 1986, to take care of its own waste. This "stick" was inserted to encourage state legislators, many of whom did not realize that most low-level waste is generated in hospital and other health facilities, to face up to their responsibility for the benefit of the people they represent. Passage of the policy act was a major step toward addressing a problem that had previously received far less attention than the issues of high-level waste disposal and interim storage of commercial spent fuel. This lack of interest was easy to understand. As long as there were three commercial sites open and providing adequate storage space, there was little incentive for other states to consider opening additional sites-to become embroiled in the troublesome issues involved in siting, licensing, constructing, and operating new sites. This situation was clearly

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

394

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

an untenable one. It placed three states-South Carolina, Washington, and Nevada--in the position of shouldering the entire responsibility for disposing of waste generated in all fifty states. The fundamental unfairness and inefficiency of this system was brought to light in the summer of 1979 when the Governors of Nevada and Washington temporarily closed those sites, and the Governor of South Carolina announced that the amount of waste accepted at the Barnwell Site would be significantly reduced in the future. By these actions, South Carolina, Washington, and Nevada sent a clear warning signal to other states and to the federal government that action needed to be taken. An immediate crisis was averted, however, when the Washington and Nevada sites were reopened in late 1979. In response to the 1980 enactment of the low-level waste law, compacts have been drafted and adopted or are under consideration in most of the states. In the northwest, a proposed compact has been ratified by Hawaii, Idaho, Oregon, Utah, and Washington; it is now before the legislatures of Alaska and Montana. The Northwest Interstate Compact on Low-Level Radioactive Waste Management recognizes that low-level wastes are generated in constructive and essential activities, that they must be managed properly within the region with a minimum of handling and transportation, and that the economies of the area will be enhanced by sharing the responsibilities of such management. Each party state has agreed to adopt practices that will require low-level waste shipments originating within its borders and destined for a facility within another state to conform to applicable package and transportation requirements and regulations of the host state. The compact provides for appropriate record keeping, inspections, penalties, and the imposition of fees by the host state upon those generating wastes and creates a Compact Committee to administer the business of the compact. The agreement of twothirds of the member states and an affirmative vote by the host state must be obtained before waste from outside the compact area may be accepted. The consent legislation for the Northwest Compact is S. 247 in the Senate. It has been referred to the Judiciary Committee and will be held at full Committee level. In the House, H.R. 1012 has been referred to the Energy and Commerce Committee, chaired by Congressman JohnDingell of Michigan, and to the Interior Committee, chaired by Congressman Morris Udall of Arizona. The Senate Judiciary Committee, under Senator Thurmond, held hearings on S. 247 during the week of March 2, 1983, along with an oversight hearing on the status of all the compacts and on issues that have surfaced in connection with them and the lowlevel waste law. Senator Thurmond is expected to wait for several more compacts to be introduced so that some comparison may be made as to how different regions are approaching the compacting process and handling the issues involved in disposal of low-level

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

25.

MCCORMACK

A View from Washington, D.C.

395

waste before bringing them to the full Senate for approval. On the other hand, he will not wait for all compacts to be introduced in Congress if that takes a long period of time. The 1986 date, after which Congressionally approved compacts may begin to exclude out-of-region waste, would appear to require approval within a year of all compacts submitted during this session of the Congress. As it is, there is likely to be a gap between the 1986 exclusionary date and the date by which some new disposal sites will be ready for operation. Senator Thurmond does not, however, support an extension of the exclusionary date as a means of resolving this problem. The Northwest Compact calls for the exclusion of waste from outside the region starting July 1, 1983. However, this will not be accepted by the Congress, and, in a compromise with those regions wishing further delay, the effective exclusionary date for all compacts will probably be held to January 1,1986, as originally provided in the law. Congress has the option of approving a compact in its entirety, rejecting the compact, or approving it subject to certain conditions. Should Congress choose to condition its approval of a particular compact, such conditions would not necessarily require subsequent action by state legislatures unless the alteration were substantial and went to the essence of the compact. This is not expected, even though Congress will move the Northwest exclusion date from July, 1983 to January 1,1986. There are options available to the states to provide for interim storage or disposal until new sites begin operation. One option is to establish interim storage facilities within the region. A second solution is to negotiate with sited regions for continued access to existing sites as long as those regions without sites have a compact in place and are making a good faith effort to designate a host state and bring a new disposal site on-line. The Northwestern and Southeastern regions of the country are moving rapidly, but there has been less progress in other parts of the country. Some states, such as Texas and California, may "go it alone" as is allowed under the law. However, a quirk in the enabling legislation does not give them the right to refuse waste from outside their respective state boundaries, as it does for compact states. The question arises as to whether or not two states such as California and Texas, even though they are not contiguous, and even though each may plan to handle its own waste within its boundaries, may enter into a compact with each other for the sole purpose of preventing the importation of waste from outside their respective states. This quirk in the law was unintentional and came about through an oversight. On January 7, 1983, President Reagan signed into law The Nuclear Waste Policy Act of 1982 for the management and storage of high-level, commercial nuclear waste and spent fuel. As a result, the Department of Energy has established a Nuclear Waste Policy Act Project Office. Its new director, Robert L. Morgan, has initiated a coordinated effort to meet the elaborate set of near-term actions that are required by this complex law.

396

GEOCHEMICAL BEHAVIOR O F RADIOACTIVE WASTE

The act requires major efforts in two primary areas, disposal and storage of spent fuel and high-level waste. This program is to be financed by a fee of 1 mil/KWhr of nuclear power produced, collected from utilities. The act provides for cooperative research, development, and demonstration activities at utility sites and federal sites. The act finds that:

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

"1. The federal government has the responsibility to provide for the permanent disposal of high-level waste and spent nuclear fuel. 2. The generators and owners of high-level waste and spent fuel have the primary responsibility to provide for, and the responsibility to pay the costs of, the interim storage of such waste and spent fuel until such waste and spent fuel is accepted by DOE. 3. State and public participation in the planning and development of repositories is essential in order to promote public confidence in the safety of disposal of such waste and spent fuel. 4. High-level radioactive waste and spent nuclear fuel have become major subjects of public concern, and appropriate precautions must be taken to ensure that such waste and spent fuel do not adversely affect the public health and safety and the environment for this or future generations." Under the act, DOE, with the concurrence of the U.S. Nuclear Regulatory Commission (NRC), has 180 days to issue guidelines for repository site recommendations. These guidelines must include consideration of geologic criteria; location of valuable natural resources; hydrology; geophysics; seismic activities; atomic energy defense activities; proximities to water supplies and population; the effect upon the rights of users of water; proximity to national parks, forests, etc.; proximity to sites where high-level radioactive waste and spent nuclear fuel is generated or stored; transportation and safety factors involved in moving such waste to a repository; the cost and impact of such transportation; and the advantages of regional distribution in the siting of repositories. To the extent practicable, DOE must recommend sites in different geologic media. A site is automatically disqualified if any surface facility of the repository is located in a highly populated area or adjacent to an area 1 mile by 1 mile having a population of not less than 1,000 individuals. The act establishes a step-by-step process by which the President, the Congress, the states, affected Indian tribes, DOE, and other federal agencies can work together in the siting, construction, and operation of a high-level nuclear waste repository. One of the priorities is to strengthen consultation and

25.

MCCORMACK

397

A View from Washington, D.C.

cooperation between DOE and affected states and affected Indian tribes. Based on the information acquired thus far, DOE believes that the states of Louisiana, Texas, Utah, Mississippi, Nevada, and Washington each contains a potentially acceptable site for a repository. Accordingly, on February 2, 1983, DOE Secretary Hodel sent letters to the governors and legislative leaders of those states formally notifying them to these findings. As an early step, DOE guidelines for the recommendation of sites for a repository were published in the Federal Register for public review and comment on February 7,1983. These guidelines will be used to identify and nominate sites for characterization and, eventually, to determine the suitability of a site for development as a repository. Through consultation with the interested governors, the Council on Environmental Q ^ty> the Environmental Protection Agency, the U.S. Geological Survey, and with the concurrence of the NRC, DOE had plans to finalize these guidelines no later than July 7,1983, as required by the act. To facilitate public involvement, DOE was holding public hearings in March in Seattle, Chicago, New Orleans, Washington, D . C , and Salt Lake City. The next step under the act is DOE's initial nomination of five locations for site characterization, based on a consideration of the guidelines and the environmental assessments to be prepared for each of the five nominated sites, followed by a recommendation of three candidate sites to the President for his approval. The DOE had intended to complete these actions in the summer of 1983 in order to permit the conduct of a sufficiently thorough site characterization program at each site to support the presidential recommendation of a site for the first repository by March 31,1987, as required by the act. The act requires that for each site under consideration, DOE conduct public hearings to solicit recommendations on issues to be addressed in the environmental assessment and in any site characterization plan to be used if the site is approved by the President. The specific date and location for these hearings will be established after consultation with state representatives. In FY 1984, the program begins a transition from the research phase to the engineering development phase. In basalt, drilling of an exploratory shaft will be completed and repository design studies will continue. In addition, at-depth testing in the preferred repository region will be initiated. In tuff, the exploratory shaft mining will be inaugurated. Confirmatory site characterization will continue. Additionally, R&D will continue on waste package design, materials characterization, and transportation studies. The aim of this overall work is to develop the data to assist a presidential site selection and subsequent repository license application for a first repository in the mid to late 1980's.

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

ua

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

398

GEOCHEMICAL BEHAVIOR OF RADIOACTIVE WASTE

By June 1, 1985, a detailed study of the need for and feasibility of construction of one or more Monitored Retrievable Storage (MRS) facilities is required. The study is to include a proposal for the construction of one or more MRS facilities and to contain at least five alternative site-specific designs at a minimum of three different sites. Implementation of the spent fuel storage provisions of the act is predicated upon the primary responsibility for storage remaining with the utilities. Federal actions are limited to: (1) encouraging and expediting effective use of existing at-reactor storage capacity through research, development, and demonstration, along with consultative assistance and (2) providing up to 1,900 metric tons of federal storage for use by utilities who have been certified by the NRC as having exhausted other reasonable alternatives. As directed by the act, DOE intends, within one year, to enter into a cooperative agreement with one to three utilities desiring DOE assistance in at-reactor demonstrations of spent fuel storage technologies. The DOE is authorized to do unlicensed demonstrations for dry storage at DOE sites using up to 300 metric tons of spent fuel. The act assigns the responsibility to DOE for interim storage of spent nuclear fuel from those civilian nuclear power reactors that cannot reasonably provide storage needed to assure their continued, orderly operation. The capacity provided by this program shall not exceed a total of 1,900 metric tons. Following an NRC determination of a utility's eligibility for interim storage, DOE will enter into contracts with the utility, take title to its fuel, provide the storage capacity for this fuel at a DOE site, ship the fuel to the storage site (using private industry under contract to provide these services), and store the fuel pending availability of disposal or other storage facilities. The act stipulates that it shall be the policy of the United States to cooperate with and provide technical assistance to nonnuclear weapon states in the field of spent fuel storage and disposal. These are only a small fraction of the requirements of that act, and they are greatly simplified in this review. Aside from making the federal government responsible for the ultimate storage of high-level commercial waste, and aside from the precedent-setting provision that the DOE will take title to spent fuel, the outstanding feature of the act is its meticulous attention to procedural details, especially in involving the public, the states where repositories may be located, and the agencies of government responsible for protection of the environment and human health and safety. It is obvious that the DOE, Secretary Don Hodel, and Project Director Robert Morgan are committed to carrying out the most demanding requirements of the law even more rigorously than required. For instance, the DOE was to hold a public hearing in

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

25.

MCCORMACK

A

View from Washington, D.C.

Richland, Washington on March 25 on the environmental assessment it has prepared with respect to the vertical exploratory shaft it is planning to excavate in basalt at Hanford. This hearing was not required. However, the DOE is reaching out to obtain public involvement in all steps it takes in implementing the waste program. Thus, the view from Washington is an optimistic one. With support of the vast amount of research, development and engineering that scientists and engineers have completed and will do in the future, this country certainly is now headed towards a successful and orderly program for handling all radioactive wastes safely and inexpensively. The high-level waste program, for instance, will require only about 2% of the cost of electricity produced from nuclear power. There is one additional subject that deserves attention at this time. It is the need for the federal government to create, by law, a public corporation for handling the fuel cycle for commercial nuclear fuel. Such a Federal Nuclear Fuel Cycle Corporation (FNFCC) would handle almost all of the nuclear power fuel cycle in a manner similar to the DOE management of the fuel cycle for the weapons program. Except for the mining and milling of uranium and the fabrication of uranium (only) fuel elements, the federal government would pre-empt ownership of all facilities used in the fuel cycle and operate them by contract with private industry (as with the weapons fuel cycle). Ownership of all fissile and fertile material (and all existing and future fuel elements) would be preempted by law and vested in the FNFCC. The FNFCC would lease fuel elements to any utility, foreign or domestic, (with IAEA supervision for foreign utilities) on condition that the fuel elements are returned for reprocessing. The United States will probably need three fuel cycle centers. Each would include a reprocessing plant, an advanced fuel fabrication facility, and a waste glassification and storage facility. The separations plants would produce a stream of blended uranium and plutonium, and a stream of waste for immediate glassification. The uranium-plutonium blend would be in such ratios as required for fuel but not for weapons production. The FNFCC would probably be controlled by a Board of Directors, nominated by the President and confirmed by the Senate. Initial financing could come from assessments against utilities for reprocessing of existing spent fuel, as for the new highlevel waste program. An assessment of 3 mils per kilowatt hour of nuclear electricity produced would probably fund all operations of the FNFCC, and all of the nuclear power research, development, and demonstraton presently funded in the DOE budget. The FNFCC would absorb the high-level waste program, Barnwell, and all enrichment facilities. Thus, all these items would be "off-budget" in the future but still approved annually by the Congress.

399

G E O C H E M I C A L BEHAVIOR O F RADIOACTIVE WASTE

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ch025

400

Private industry would perform all operations on cost-plus contracts, thus eliminating potential conflicts between safety and profits. Small nations with a few nuclear power plants would find it cheaper to lease fuel from the FNFCC than to try to reprocess it themselves. This would constitute a major, realistic, nonproliferation initiative. Candidate nations include the Republic of China, South Korea, the Philippines, Argentina, and Brazil. Reprocesing fuel to extract and glassify waste for permanent geologic disposal is the most attractive method for handling spent fuel from a safety and environmental perspective. Also recycling fuel is probably more environmentally attractive than mining more uranium, especially from lower grade ores. This concept of an FNFCC has been suggested to the Adminstration and to some Congressional leaders. There has been no known opposition expressed, but there is some indication of a reluctance to undertake such a major problem-solving initiative in one step. RECEIVED

December 12, 1983

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix001

Author Index Aldred, A. T., 305,315 Ames, L. L., 67 Arnold, W. D., 79 Barney, G. S., 3,95 Bernkopf, Μ., 115 B i b l e r , Ned E., 359 Bo, Peter, 167 Bowers, D. L., 229 Brown, D. L., 217 Burger, L. L., 373 Brozdowski, Robert, 197 Carlsen, Lars, 167 Case, F. I., 79 Choi, In-Kyu, 323 Danielson, Michael J . , 197 Delegard, C. H., 95 Deutsch, W. J . , 287 Drewes, D. R., 147 E a r l y , T. 0., 147 Edwards, K. W., 271 Ensor, D. D., 335 F r i e d , S. Μ., 229 Fulton, Robert W., 135 Gallagher, S. Α., 95 George, I. Μ., 25 Gerding, T. J . , 229 Grandstaff, David Ε., 197 Haines, R. I., 217 Haire, R. G., 335 Jacobs, G. Κ., 147 Jones, T. Ε., 181 Kim, J . I., 115 Kirby, L. J . , 251 Koppold, F., 115 Koski, Oscar Η., 197 Une, D. L., 181 Larsen, G i t t e , 167

L i e r s e , Ch., 115 Machiels, A. J . , 349 McCormack, M. 389 McGarrah, J . E., 67 Melnyk, T. W., 45 Meyer, R. E., 79 Morss, Lester R., 323 Myers, Jonathan, 197 N e v i t t , M. V., 315 Owen, D. G., 217 Pahl, T. R., 251 Palmer, D. Α., 79 Pescatore, C , 349 Peterson, J . R., 335 Rai, Dhanpat, 135 Ross, J . P. M., 45 Scheele, R. D., 373 S e i t z , M. G., 229 Seme, R. J . , 287 Shade, J . W., 67 Skeet, Α. Μ. Μ., 45 S t a n c h e l l , F. W., 217 S t r i c k e r t , Richard G., 135 Ticknor, Κ. V., 25 Toste, A. P., 251 Ulmer, Gene C., 197 Vandegrift, G. F., 229 Vandergraaf, T. T., 25 Walton, F. B., 45 Watson, D. G., 217 West, M. H., 181 Wiemers, K. D., 373 Wilbur, C. Κ., 229 Williams, Clayton W., 323 Yang, I. C , 271 Young, J . P., 335

403

Subject Index

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

A

Americium(III) absorption spectra, 131f hydrolysis products vs. hydroxide, 131f hydrolysis reactions, 115-32 Americium hydroxide, s o l u b i l i t y , 117,123f Americium oxide, s o l u b i l i t y , 120-22,123f Analog experiments, 230 apparatus, 231f,233-34 Anoxic systems, 122 Antimony, presence of s u l f u r , 153 Aqueous s u l f i d e , 152 Arsenic(III)-arsenic(V) r e a c t i o n , 188 redox p o t e n t i a l c a l c u l a t i o n s , 190 Arsenic(V), reduction to As ( I I I ) , 18Î Arsenic oxidation s t a t e , 184 data, I86t determinations, method, 184 determining Eh, 182 Arsenic redox reactions, r a t e s , 188 Arsenic-water system, Eh-pH diagram, l89f Atomic absorption spectroscopy, 184 Auger spectra, of mineral surfaces, 218

AAS—See Atomic absorption spectroscopy Actinide(IV) perovskites, 324 Actinides alpha emission, 336 beta emission, 336 bulk-phase oxidation s t a t e , 337 concentration, determination, 117 migration, 229-46 i n the rock core, 242-45 rate of unaltered basalt, 246 retardation data, discussion, 245 sorption basalt f i s s u r e s , 244t on c l a y c o l l o i d s , 67-77 on i r o n - s i l i c a t e , 67-77 s t a b i l i t y , 323 tetravalent, s t a b i l i t y i n perovskites, 323-34 Active coupons chemical e x t r a c t i o n , 53-55 experiments, 48 Albite cesium concentration, 225 elemental binding energies, 223t i n granite groundwater, 220 scanning electron microscopy, 219 Alkaline-earth elements basalt core, e f f e c t s , 238 e f f e c t s of bentonite, 238 Alpha decay consequences i n s o l i d s t a t e , 335-46 s o l i d state d i l u t i o n s , 342-45 Alumina cesium sorption, 85f europium sorption, 85f strontium sorption, 82f,85f Aluminate i o n neptunium sorption e f f e c t s , 106 Plutonium sorption e f f e c t s , 106 Americium determination, 255 d i r e c t s p e c i a t i o n , 129 excess, polymer formation, 120 hydrolyzed species, 118 oxidation-reduction behavior, 101 pH changes, 123f r e t a r d a t i o n f a c t o r s , 108 s o l u b i l i t y , 102 s o l u b i l i t y constant determination, 118,121 sorption, 12,20t,21

Β B a c k f i l l , bentonite, 233 B a r b i t a l , 267 Barium compounds enthalpies of s o l u t i o n , 327,328t preparation, 326 thermochemical c y c l e s , 329t Barium iodate-cement, leach t e s t s , 38lf Basalt arsenic oxidation s t a t e s , 184 crushed a d d i t i o n to bentonite, 191 as b a c k f i l l , 182 crushing, 191 dissolved oxygen vs. time, I89f engineered i s o l a t i o n parameters, 14 i n granite groundwaters, 296 nuclear waste repository oxygen consumption, 181-96 redox conditions, 181-96 s o l u b i l i t y r e l a t i o n s h i p s , 150 temperature e f f e c t s , 160 radionuclide releases i n , 147-63

404

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

INDEX Basalt radionuclide releases in—Continued redox p o t e n t i a l , a r s e n i c o x i d a t i o n d a t a , I86t sample p r e p a r a t i o n , 183 unaltered, role i n actinide m i g r a t i o n , 246 Basalt cores effects o f a l k a l i n e - e a r t h e l e m e n t s , 238 o f c a l c i u m i o n , 238 on g r o u n d w a t e r , 235 o f sodium i o n , 235 fissured h y d r o a l t e r a t i o n , 235 t h e r m o a l t e r a t i o n , 235 f i s s u r e s , neptunium s o r p t i o n , 243f B a s a l t f i s s u r e s u r f a c e s , groundwater i n t e r a c t i o n w i t h , 229-46 B a s a l t f i s s u r e s , s o r p t i o n of a c t i n i d e s , 244t B a s a l t g r o u n d w a t e r , c o m p o s i t i o n , 297t Basalt-water systems, reducing a g e n t s , 188 Bentonite a d d i t i o n t o b a s a l t b a c k f i l l , 191 b a s a l t b i n d i n g , 246 effects on a l k a l i n e - e a r t h e l e m e n t s , 238 on c a l c i u m - i o n , 238 on g r o u n d w a t e r , 235 on s o d i u m - i o n , 235 h y d r o a l t e r a t i o n , 235 i n t e r a c t i o n w i t h g r o u n d w a t e r , 238 neptunium s o r p t i o n o n , 74 t e c h n e t i u m s o r p t i o n o n , 74 t h e r m o a l t e r a t i o n , 235 t r a n s p o r t , 246 B e n t o n i t e b a c k f i l l , 233 B e n t o n i t e c l a y , p r o p e r t i e s , 234 Berkelium a l p h a e m i s s i o n , 336 b e t a d e c a y , c r y s t a l s t r u c t u r e , 338 B e t a decay consequences i n s o l i d s t a t e , 335-46 s o l i d s t a t e d i l u t i o n s , 342-45 B i t u m e n , i o d i n e i m m o b i l i z a t i o n , 376 B l i n d - t e s t s , 168 Borosilicate glass brine l e a c h i n g , 363,365,366t c h a r a c t e r i z a t i o n , Savannah R i v e r p l a n t , 359-72 c o m p o s i t i o n , 361t l e a c h a n t a c t i v i t y , 367t leaching i n deionized water, 363,364f l e a c h i n g , 355,362-69 l o n g - t e r m l e a c h i n g , 366t n i t r i c a c i d e f f e c t s , 369

405 Borosilicate glass—Continued p r e p a r a t i o n and c o m p o s i t i o n , 360 s i l i c a t e water l e a c h i n g , 363,364,366t s u r f a c e a r e a e f f e c t s , 369 B r i n e , 360 e f f e c t on b o r o s i l i c a t e g l a s s , 367t Brine leaching b o r o s i l i c a t e g l a s s , 363,365 use o f p l a t i n u m , 362 B u l k p h a s e , i o n exchange, 352 C C a l c i u m , e f f e c t on s t r o n t i u m s o r p t i o n , 19 Calcium iodate-cement, leach t e s t s , 382f Calcium ions b a s a l t c o r e , e f f e c t s , 238 e f f e c t s o f b e n t o n i t e , 238 steady-state attainment, 236f,237f Californium s p e c t r u m i n samarium t r i b o m i d e , 345 s t a b i l i t y , 336 C a l i f o r n i u m bromide, orthorhombic form, 338,339f CANDU, 26 C a n i s t e r c o r r o s i o n , r a t e e f f e c t s , 198 C a r b o n a t e i n g r o u n d w a t e r , uranium s o l u b i l i t y , 287 Cement, l e a c h r e s i s t a n c e , i o d i n e , 383 Cerium i r o n e f f e c t s , 62-63 model f i t s , 64 Cerium-144, double f i r s t - o r d e r m o d e l , 58t Cesium humic a c i d i n t e r a c t i o n , 175t humic a c i d s o r p t i o n , 174 i n t e r a c t i o n w i t h f e l d s p a r s , 217-28 i r o n e f f e c t s , 62 Cesium-137, double f i r s t - o r d e r m o d e l , 58t Cesium i s o t h e r m s , 10f Cesium s o r p t i o n , 19 on c l a y , 82f on gamma-alumina, 8 5 f v a r i a b l e s , 20t Charge-compensated i o n i m p l a n t a t i o n , 342 C h e l a t i n g a g e n t s , 265 Chemical e x t r a c t i o n g r a n i t i c r o c k , 45-66 s e l e c t i v e , model p r e d i c t i o n s , 59t C h l o r i d e , i n g r a n i t e g r o u n d w a t e r s , 296 Clay b e n t o n i t e , p r o p e r t i e s , 234

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

406

G E O C H E M I C A L BEHAVIOR O F RADIOACTIVE WASTE

Clay—Continued cesium sorption, 82f europium sorption, 82f ideal d e f i n i t i o n , 80 isotherms, 80-81 n a t u r a l , 88 strontium sorption, 82f t r i v a l e n t i o n sorption, 91f Clay c o l l o i d s , a c t i n i d e sorption on, 67-77 Cobalt double f i r s t - o r d e r model, 58t humic a c i d i n t e r a c t i o n , 174,175t s o l u b i l i t y , 98 Cobalt-60, EDTA c o e l u t i o n , 268 Cobalt sorption onto oxyhydroxides, 62 Plackett-Burman t e s t , 104 C o f f i n i t e , 290 C o l l o i d species, v e r i f i c a t i o n of existence, 125 C o l l o i d zeta p o t e n t i a l , 73f C o l l o i d a l i r o n sorption cesium, 76f strontium, 76f Columbia River basalt formation interbed materials, 3-24 groundwaters, 5 synthetic groundwater compositions, 6t Combined isotherms, 87-93 Complexing agents, organic, i n groundwat ers, 161 Contaminated groundwater, migration, 198 Counterdiffusion, glass matrix, 353 Crushed basalt a d d i t i o n to bentonite, 191 b a c k f i l l , 182 C r y s t a l l i n e matrices f o r nuclear waste d i s p o s a l , 324 D Desorption isotherms, 9 Desorption measurements, 8 Desorption r e a c t i o n , radionuclides, 3-24 Dialysis information obtained, 167 radionuclide-humic a c i d i n t e r a c t i o n s , 167-78 D i s s o l u t i o n process, 162 Dissolved oxygen absence of basalt, 190 basalt, 186 f i r s t - o r d e r rate constant, 190 vs. time, basalt, I89f

Dissolved species, s p e c i a t i o n , 125-32 Distribution coefficients, trivalent ion sorption, 89f,91f Double f i r s t - o r d e r model, 55 comparison to m i x i n g - c e l l data, 56f,57t parameters, 58t

Ε EDTA chemical s t r u c t u r e , 266f cobalt-60 c o e l u t i o n , 268 e f f e c t on r a d i o a c t i v e sorption, 96-110 EDTA-like species, 265 Eh See a l s o Redox p o t e n t i a l basalt-groundwater system, 152 Grande Ronde groundwater, 152 neptunium s o l u b i l i t y , 156f n i c k e l s o l u b i l i t y , 154f Plutonium s o l u b i l i t y , 156f selenium s o l u b i l i t y , 154f t i n s o l u b i l i t y , 155f uranium s o l u b i l i t y , 155f Einsteinium alpha emission, 336 bulk phase, 337 growth and decay, 339f Einsteinium bromides progeny vs. parent absorption peaks, 340t spectra i n lanthanide bromides, 344f spectra, 34lf Einsteinium c h l o r i d e s , progeny vs. parent absorption peaks, 342t Einsteinium halides long-range order, 338 progeny species, 342 Empirical d i s t r i b u t i o n c o e f f i c i e n t , 4 Enhanced sorption, 83 Equilibrium constant, i o n exchange r e a c t i o n , 81 Equilibrium d i s t r i b u t i o n c o e f f i c i e n t , ion exchange r e a c t i o n , 81 Europium adsorption corundum, 92f montmorillonite, 88,89f sorption c l a y , 82f gamma-alumina, 85f loading e f f e c t , 86f to c e l l u l o s e , 174 Europium-fulvic a c i d complex, s t a b i l i t y , 174 E x t r a c t i o n , h i g h - l e v e l waste, 392

INDEX

407

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

F Feldspars a l t e r a t i o n product i n a c i d , 226 elemental binding energies, 223t Fourier transform IR spectra, 219 Fergusonite, s t r u c t u r e , 306 Ferrous i r o n from mesostasis, 188 Ferrous iron-containing minerals, technetium sorption, 31-37 F i r s t - o r d e r model comparison to m i x i n g - c e l l data, 57t double, 55 Fourier transform i n f r a r e d spectra of f e l d s p a r s , 219 Freundlich equation, 4 assumption, 12 comparison to m i x i n g - c e l l data, 57t Freundlich isotherm, net rate of sorption, 47 Fuel cycle centers, 399 F u l v i c a c i d , 167 G Gabbro, technetium sorption c o e f f i c i e n t s , 31t Gabbro rock f e l d s p a r s , 217 Gamma counting, 168 Gamma r a d i a t i o n e f f e c t on leaching, 246 groundwater composition e f f e c t s , 246 Gamma-ray spectrometry, 255 Glass matrix, s e l e c t i v e leaching, 352 Glass waste form radionuclide r e l e a s e s , 162 leaching, 349 G l a s s - s o l u t i o n i n t e r f a c e , ion exchange, 352 Grande Ronde groundwater composition, 157t,232t dissolved oxygen, I87t Eh values, 152 pH value, 151 s u l f a t e , 152 s y n t h e t i c , a n a l y s i s , I83t Granite cesium concentrations, 225 i r o n e x t r a c t i o n , 51 Lac du Bonnet, 49t i r o n e x t r a c t i o n r a t e s , 52f s e l e c t i v e chemical e x t r a c t i o n , 61 technetium sorption c o e f f i c i e n t s , 31t Granite coupons, photographs, 54f Granite f e l d s p a r s , 217 Granite groundwater albite,220 composition, 297t microcline, 220

G r a n i t i c f e l d s p a r s , cesium concentrations, 225 Groundwater contaminated, migration, 198 e f f e c t on radionuclide sorption, 16-22 e f f e c t s of basalt cores, 235 e f f e c t s of bentonite, 235 Grande Ronde composition, 232t Eh values, 152 pH values, 151 i n t e r a c t i o n with basalt f i s s u r e surfaces, 229-46 i n t e r a c t i o n with bentonite, 238 organic complexing agents, 161 redox p o t e n t i a l , e f f e c t s , 22

H Hanford h i g h - l e v e l waste components, e f f e c t on s o l u b i l i t y and s o r p t i o n , 95-112 Hanford Reservation, l o c a t i o n , 181 High-level waste, e x t r a c t i o n , 392 Hot i s o s t a t i c pressing o f lanthanum compounds, 317-20 Humate anions cobalt i n t e r a c t i o n , 174 europium i n t e r a c t i o n , 174 metal ions r e a c t i o n , 169 Humic a c i d , 30 complexing capacity, 176-177 complexing s i t e s , 171 d i s s o c i a t i o n , 169 importance of o r i g i n , 176 sorption of cesium, 174 s o r p t i o n of strontium, 174 Humic a c i d - a c i d i n t e r a c t i o n s , d i a l y s i s s t u d i e s , 167-78 Humic acid-metal i o n i n t e r a c t i o n equation, 170 f r e e ligand concentration, 170 Hybride generation-flame atomic absorption spectroscopy, 184 Hydrazine neptunium sorption, 21 plutonium sorption, 21 technetium sorption, 19 Hydroalteration bentonite, 235 f i s s u r e d basalt cores, 235 Hydrolysis, americium(III), 115-32 Hydrophilic organic compounds, Maxey F l a t s , 259t,26lt Hydrophobic organic compounds, Maxey F l a t s , 263t,264t Hydrothermal experiments, monitoring Eh-pH conditions, 197-216

408

G E O C H E M I C A L BEHAVIOR O F RADIOACTIVE WASTE

Hydrous oxides adsorption c h a r a c t e r i s t i c s , 81 isotherms, 81-87 nuclide adsorption, 79-94 s o l u b i l i t y e f f e c t s , 160 Hydroxides, s o l u b i l i t y e f f e c t s , 160 Hydroxyethylethylenediaminetriacetic a c i d , 96-110 Hysteresis, d e f i n i t i o n , 4

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

I Ideal c l a y , d e f i n i t i o n , 80 Ideal hydrous oxides, isotherms, 81-87 In s i t u leach mining, 288,291 In s i t u uranium mine, well pattern, 292f Inactive coupon experiments, Lac du Bonnet g r a n i t e , 48-50 I n i t i a l containment, 198 Interbeds definition, 5 mineralogical c h a r a c t e r i s t i c s , 7t Interbed s o l i d s , p r e c i p i t a t i o n , 4 Iodates leach t e s t s , 382f s o l u b i l i t y ranking, 378t Iodides, s o l u b i l i t y , 376,377 Iodine b i o l o g i c a l s i g n i f i c a n c e , 373 capture technologies, 375t immobilization form, 375-77 leach r e s i s t a n c e , 377,383 leaching, f a c t o r s , 379 reduction, 380 release mechanism, 375 Iodine-129 disposal strategy, 374-75 h a l f - l i f e , 373 production r a t e , 373t p r o p e r t i e s , 373t transportation requirements, 374 Iodine-cement monoliths, c h a r a c t e r i s t i c s , 380t Iodine compounds, leach r e s i s t a n c e , 373-88 Ion exchange bulk phase, 352 g l a s s - s o l u t i o n i n t e r f a c e , 352 Ion exchange r e a c t i o n , equilibrium d i s t r i b u t i o n c o e f f i c i e n t , 81 Ion implantation, chargecompensated, 342 Iron hydroxides, sorption, 61 Iron oxides, technetium s o r p t i o n , 37 Iron oxyhydroxides, technetium s o r p t i o n , 37 Iron s i l i c a t e c o l l o i d s , preparation, 68

Iron s i l i c a t e sorption, 70t neptunium, 75f Plutonium, 72f r a d i o n u c l i d e s , 69 technetium, 75f uranium, 72f Iron sorption cesium, 76f strontium, 76f Iron-containing minerals, technetium reactions with, 25-44 Iron-silicate a c t i n i d e s o r p t i o n , 67-77 technetium s o r p t i o n , 67-77 Isotherms, 9 cesium, 10f combined, 87-93 f o r i d e a l c l a y , 80-81 f o r i d e a l hydrous oxides, 81-87 neptunium, 14f selenium, 17f technetium, 17f uranium, 10f,15f Κ K a o l i n i t e , 226 L Labradorite, 217 elemental binding energies, 223t f i n e s , 224f r e a c t i o n with cesium c h l o r i d e , 221f Lac du Bonnet granite a c t i v e coupon experiments, 48 chemical composition, 28t,49t i n a c t i v e coupon experiments, 48-50 i r o n e x t r a c t i o n r a t e s , 52f mineral composition, 29t Langmuir sorption isotherm comparison to m i x i n g - c e l l data, 57t net r a t e of s o r p t i o n , 47 Lanthanide compounds c r y s t a l chemistry, 305-14 polymorphism, 306 Lanthanide h a l i d e s , einsteinium t r i h a l i d e incorporation, 343 Lanthanum compounds hot i s o s t a t i c pressing, 317-20 l a t t i c e parameters, 3l8f s p e c i f i c heat, 3l8f transformation c h a r a c t e r i s t i c s , 315-22 transformation temperature, 319f Lanthanum sesquioxide, 307 Leach mining, i n s i t u , 288 process, 291 of uranium, 290-91

409

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

INDEX Leach rates asymptotic, 353 g l a s s , 67 sodium-bentonite b a c k f i l l materials, 67 Leach r e s i s t a n c e , of iodine compounds, 373-88 Leach r e s u l t s , c a l c u l a t i o n , 362 Leachability radium-226, 284 uranium, 284 Leaching e f f e c t s of water flow r a t e s , 349-58 flow r a t e , network d i s s o l u t i o n e f f e c t s , 350-52 mechanisms, flow conditions, 354 network d i s s o l u t i o n c o n t r o l , 351 s e l e c t i v e , without s a t u r a t i o n , 354 vs. time, 357f Lead, presence of s u l f u r , 153 L e g i s l a t i v e views, 391-400 L i x i v i a n t , i n t e r a c t i o n with sediment, 231 Loading e f f e c t cesium s o r p t i o n , 86f europium sorption, 86f strontium s o r p t i o n , 86f Long-range order, 338 Low-Level Radioactive Waste P o l i c y Act of 1980, 393 Low-level waste, generation, 393 M Mabton Interbed, 6,7t Mabton Interbed s o l i d s h y s t e r e s i s , 18 neptunium sorption, I4f selenium s o r p t i o n , 17f technetium sorption, 17f uranium s o r p t i o n , 15f Material balance, transmutation, 338-42 Maxey F l a t s , 252 groundwaters, organic content, 258-67 h y d r o p h i l i c organic compounds, 259t,26lt hydrophobic organic compounds, 263t,264t organic analyses, 255-56 radionuclide migration, groundwater movement, 257 s t e r i c exclusion chromatography, 269f study area, 254f Mesostasis, 188 Metal ion3, r e a c t i o n with humate anions, 169 Metal ion-humic a c i d i n t e r a c t i o n , 170

Metal i o n - s o i l organic matter i n t e r a c t i o n s , 167 M i c r o c l i n e , 217 cleaved, 222f elemental binding energies, 223t f i n e s , 224f i n g r a n i t e groundwater, 220 r e a c t i o n with cesium c h l o r i d e , 221f scanning e l e c t r o n microscopy, 219 Migration and organics, 267-69 r a d i o n u c l i d e , dependence, 230 M i x i n g - c e l l , 52f M i x i n g - c e l l data, model f i t t i n g , 63 M i x i n g - c e l l experiments, models, 50 Monazite polymorphism, 313 s t r u c t u r e , 306 Monitored r e t r i e v a b l e storage f a c i l i t i e s , 398 Montmorillonite, 93 Ν Natural c l a y , 88 Natural p o l l u c i t e , grown on m i c r o c l i n e , 224f Neptunium chemical separation, 234 Freundlich constants, 13t oxidation-reduction behavior, 101 sodium hydroxide e f f e c t s , 101 s o l u b i l i t y , 101 vs. Eh, 156f s o l u t i o n , behavior, 140 sorption and desorption isotherms, I4f Neptunium-237 stock s o l u t i o n , preparation, 136 Neptunium hydrous oxide aging e f f e c t s , 135-44 c r y s t a l l i n i t y development, 136 e q u i l i b r a t i o n time e f f e c t , 139f e q u i l i b r a t i o n time vs. pH, I42f equilibrium, pH e f f e c t , 138f pH e f f e c t s , 137-42 Neptunium oxidation s t a t e analyses, 14Of Neptunium sorption a d d i t i v e s e f f e c t , 108 on bentonite, 74 hydrazine e f f e c t s , 21 Mabton interbed s o l i d s , I4f v a r i a b l e s , 20t Neptunium suspensions oxidation s t a t e analyses, I43t s o l i d phase analyses, 143 X-ray d i f f r a c t i o n analyses, I44t Network d i s s o l u t i o n e f f e c t s , leaching flow r a t e , 350-52 .

410

GEOCHEM1CAL BEHAVIOR O F RADIOACTIVE WASTE

N i c k e l , presence of s u l f u r , 153 N i c k e l , s o l u b i l i t y v s . Eh, 154f Niobate compounds, 307 Nuclear Waste P o l i c y Act of 1982, 391,395-96 Nuclear waste r e p o s i t o r y basalt oxygen consumption, 181-96 parameters, 148 redox conditions, 181-96 s o l u b i l i t y r e l a t i o n s h i p s , 150 temperature e f f e c t s , 160 l i c e n s i n g r e g u l a t i o n s , 135 Nuclide, adsorption, on hydrous oxides, 79-94

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

0 O l i v i n e Gabbro chemical composition, 28t mineral composition, 29t One-dimensional transport, equation, 4 Organic complexing agents i n groundwat ers, 161 Organics and radionuclide migration, 267-69 Organics, subsurface migration r o l e , 251-70 Oxides adsorption c h a r a c t e r i s t i c s , 81 adsorption v s . pH, 84f i d e a l hydrous, isotherms, 81-87 s o l u b i l i t y e f f e c t s , 160 sorption, 83 Oxygen consumption i n b a s a l t , 180-96 i n b a s a l t — S e e also Dissolved oxygen e f f e c t of crushing basalt, 191 Ρ

pH v a r i a t i o n , causes, 203 Plackett-Burman design, 96 Pluton, igneous rock, 217 Plutonium chemical separation, 234 determination, 255 d i r e c t s p e c i a t i o n , 129 Freundlich constants, 13t hexavalent vs. t e t r a v a l e n t , 252 oxidation-reduction behavior, 101 recoverable, 392 Plutonium-239, f i s s i o n i n g , 26 Plutonium(VI) absorption spectra, 124f hydrolysis products, 125,132 hydrolysis reactions, 115-32 sorption of dissolved species, 129 Plutonium hydroxide, s o l u b i l i t y , 122-25 Plutonium s o l u b i l i t y , 124f a d d i t i v e s e f f e c t , 104 sodium hydroxide e f f e c t s , 101 vs. Eh, 156f Plutonium sorption a d d i t i v e s e f f e c t , 106 hydrazine e f f e c t s , 21 v a r i a b l e s , 20t Pollucite elemental binding energies, 223t formula, 217 grown on m i c r o c l i n e , 224f Polypropylene, r a d i a t i o n s t a b i l i t y , 362 Polyvalent ions, sorption, pH e f f e c t , 93 Portland cement, leach r e s i s t a n c e , 373-88 P r e c i p i t a t i o n , on interbed s o l i d s , 4 Promethium, 26 Q

Palladium, presence of s u l f u r , 153 Pasco Basin, stratigraphy, I49f Pentafluorobenzoic a c i d , 253 Pentobarbital, 267 Perovskites enthalpies of formation, 330f enthalpies of s o l u t i o n , 327,328t preparation, 326 s t r u c t u r e s , 325f,332t thermochemical c y c l e s , 329t thermodynamic parameters, 332t pH, e f f e c t on sorption of polyvalent ions, 93 pH electrodes, c a l i b r a t i o n and evaluation, 206 pH response, z i r c o n i a pH sensors, 204,206 pH sensing mechanisms, 214 pH t e s t i n g system, pumpable, 207f

Quartz, technetium sorption c o e f f i c i e n t s , 31t R Radioélément d i s t r i b u t i o n c o e f f i c i e n t s , p r e d i c t i o n , 106 Radionuclides desorption reactions, 3-24 one-dimensional transport, equation, 4 sorption r e a c t i o n s , 3-24 Radionuclide s o l u b i l i t y , temperature e f f e c t s , 160 Radionuclide sorption groundwater composition e f f e c t s , 15-22 mathematical models, 47

411

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

INDEX Radionuclide sorption—Continued mechanisms, determination, 45-66 redox p o t e n t i a l e f f e c t s , 16-22 r e t a r d a t i o n , 46 Radium Freundlich constants, 13t release from Ralston Creek, 271-86 Radium-226 concentration p a r t i c l e s i z e e f f e c t s , 282f Ralston Creek, 272,275 distribution p a r t i c l e s i z e e f f e c t , 279f Ralston Creek, 280,28lt l e a c h a b i l i t y from Ralston Creek, 283t leaching e f f i c i e n c y , 281t Radon t r a n s f e r system, 274f Ralston Creek bottom sediments, 278-80 dissolved radium-226, 277f dissolved uranium, 277f leaching s t u d i e s , 280-84 radium-226 concentrations, 272,275 and Reservoir, map, 274f suspended s o l i d s , 276 uranium concentrations, 275 Ralston Reservoir radium-226 concentration, 276 uranium concentration, 276 Rattlesnake Ridge interbed, mineralogical c h a r a c t e r i s t i c s , 7t Rattlesnake Ridge sandstone, radionuclide sorption, 11t Redox conditions basalt nuclear waste r e p o s i t o r y , 181-96 e f f e c t of crushing basalt, 191 Redox p o t e n t i a l arsenic(III)-arsenic(V) c a l c u l a t i o n s , 190 e f f e c t on radionuclide sorption, 16-22 groundwater, 22 monitoring, 182 Redox-pH conditions, i n hydrothermal experiments, 197-216 Reduced minerals, i n t e r a c t i o n with uranium, 291-95 Release mechanism, i o d i n e , 375 Resistance measurements, z i r c o n i a pH sensors, 206 Retardation f a c t o r , 4 R o l l - f r o n t deposits composition, 287-302 uranium concentration, 288-290 uranium m o b i l i t y , 287-302

S Savannah River Plant b o r o s i l i c a t e glass leachant a c t i v i t y , 367t long-term leaching, 366t waste, immobilization, 359 S c h e e l i t e , s t r u c t u r e , 306 Schwartzwalder uranium mine, 272 S e l e c t i v e chemical e x t r a c t i o n g r a n i t e , 61 model p r e d i c t i o n s , 59t S e l e c t i v e leaching, 352-54 Selenium i r o n e f f e c t s , 62 precipitation, 9 s o l u b i l i t y vs. Eh, 154f sorption and desorption isotherms, 17f s o r p t i o n , v a r i a b l e s , 20t Selenium-75, double f i r s t - o r d e r model, 58t Sensors, monitoring Eh and pH, 198 S i l i c a d i s s o l u t i o n r e a c t i o n s , 350-51 Silicates s o l u b i l i t y e f f e c t s , 160 water leaching, b o r o s i l i c a t e g l a s s , 363,365 water, e f f e c t on b o r o s i l i c a t e g l a s s , 367t Silicon electron-beam-induced reduction, 223 d i s s o l u t i o n , leach r a t e , equation, 350 leaching equilibrium pH, 355 from b o r o s i l i c a t e g l a s s , 354-55 r a t e , congruent d i s s o l u t i o n , 356f S i l v e r iodide-cement leach t e s t s , 38lf matrix, 380 Single f i r s t - o r d e r model, comparison to m i x i n g - c e l l data, 56f Sodium, e f f e c t on strontium s o r p t i o n , 19 Sodium bentonite b a c k f i l l materials, leach r a t e s , 67 c o l l o i d s , preparation, 68 s o r p t i o n , 71t Sodium bromide, 253 Sodium i o n e f f e c t s i n basalt cores, 235 e f f e c t s of bentonite, 235 steady-state attainment, 236f,237f Sodium leaching equilibrium pH, 355 from b o r o s i l i c a t e g l a s s , 354-55

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

412

G E O C H E M I C A L BEHAVIOR O F RADIOACTIVE WASTE

Sodium m o n t m o r i l l o n i t e , 233 S o l i d s t a t e d i l u t i o n s , 342-45 Sorbed r a d i o n u c l i d e s v s . s o r p t i o n mechanisms, 56f Sorption a m e r i c i u m , 12 c e s i u m i s o t h e r m s , 10f e n h a n c e d , 83 F r e u n d l i c h i s o t h e r m , 47 Langmuir s o r p t i o n i s o t h e r m , 47 n e t r a t e , 47 r a d i o n u c l i d e , mathematical m o d e l s , 47 t i n , 12 u r a n i u m i s o t h e r m s , 10f S o r p t i o n c o e f f i c i e n t s , e q u a t i o n , 31 Sorption isotherms, 9 m i x i n g - c e l l d a t a , 55 S o r p t i o n mechanisms, 46 v s . s o r b e d r a d i o n u c l i d e s , 56f S o r p t i o n r a t e p a r a m e t e r , e q u a t i o n , 46 Sorption reactions, r a d i o n u c l i d e s , 3-24 Speciation a m e r i c i u m , 129 o f d i s s o l v e d s p e c i e s , 125-32 P l u t o n i u m , 129 Spent f u e l s t o r a g e , f e d e r a l a c t i o n s , 398 Spent n u c l e a r f u e l , r e c o v e r a b l e , 392 S t a t e r e s p o n s i b i l i t i e s , 393 S t e r i c e x c l u s i o n c h r o m a t o g r a p h y , Maxey F l a t s , 269f Strontium humic a c i d c o m p l e x e s , c o m p o s i t i o n , 176 humic a c i d i n t e r a c t i o n , 175t humic a c i d s o r p t i o n , 174 s o l u b i l i t y , 98 a d d i t i v e s e f f e c t , 102 S t r o n t i u m r e t a r d a t i o n f a c t o r s , 108 Strontium sorption a d d i t i v e s e f f e c t , 106 a l u m i n a , 82f c a l c i u m e f f e c t s , 19 c l a y , 82f gamma-alumina, 85f l o a d i n g e f f e c t , 86f sodium e f f e c t s , 19 v a r i a b l e s , 20t Subsurface m i g r a t i o n f a c t o r s , 252 r o l e of o r g a n i c s , 251-70 S y n t h e t i c Grande Ronde g r o u n d w a t e r , a n a l y s i s , I83t

Τ Technetium concentration, decreases, 38f,39f e f f e c t of ferrous-containing m i n e r a l s , 33 Eh-pH d i a g r a m , 27f F r e u n d l i c h c o n s t a n t s , 13t h a l f - l i f e , 26 w i t h i r o n , Eh-pH d i a g r a m , 2 7 f precipitation, 9 reactions with iron-containing m i n e r a l s , 25-44 s u b s u r f a c e m i g r a t i o n , 252 Technetium s o r p t i o n , 31-37 b e n t o n i t e , 74 b i o t i t e m i c a , 34f c o e f f i c i e n t s , 31t on G a b b r o , 33t on g r a n i t e , 33t and d e s o r p t i o n i s o t h e r m s , 17f f e r r o u s - i r o n - c o n t a i n i n g m i n e r a l s , 33t g a b b r o , 32f g r a n i t e , 36f h o r n b l e n d e , 35f h y d r a z i n e e f f e c t s , 19 i r o n o x i d e s , 37 i r o n - s i l i c a t e , 67-77 s t u d i e s , c h e m i c a l c o m p o s i t i o n , 29t under a n o x i c c o n d i t i o n s , 31 under o x i c c o n d i t i o n s , 30-31 v a r i a b l e s , 20t Teflon p r o p e r t i e s , 199 r a d i a t i o n s t a b i l i t y , 362 T e f l o n hydrogen d i f f u s i o n membranes, 199-202 c a l i b r a t i o n , 200 c o b a l t - c o b a l t o x i d e b u f f e r s , 201t i r o n - i r o n o x i d e b u f f e r s , 201t Tetravalent a c t i n i d e s , s t a b i l i t y i n p e r o v s k i t e s , 323-34 Thermoalteration b e n t o n i t e , 235 f i s s u r e d b a s a l t c o r e s , 235 Tin s o l u b i l i t y v s . E h , 155f s o r p t i o n , 12 Transmutation, 235-36 m a t e r i a l b a l a n c e , 338-42 T r a n s p o r t , b e n t o n i t e , 246 Transport equation, 4 Trivalent ion sorption, distribution c o e f f i c i e n t s , 89f,91f T u f f g r o u n d w a t e r , c o m p o s i t i o n , 297t

413

INDEX

Publication Date: March 8, 1984 | doi: 10.1021/bk-1984-0246.ix002

υ Umtanum b a s a l t m e s o s t a s i s , f e r r o u s i r o n c o n t e n t , 190 uranium, concentration, p a r t i c l e size e f f e c t s , 282f c o n c e n t r a t i o n s i n R a l s t o n C r e e k , 275 d e s o r p t i o n , 12 d e t e r m i n a t i o n , 273 d i s t r i b u t i o n , 28lt particle size e f f e c t , 279f d i s t r i b u t i o n i n R a l s t o n C r e e k , 280 f i s s i o n i n g , 26 form i n R a l s t o n C r e e k , 278 F r e u n d l i c h c o n s t a n t s , 13t h e x a v a l e n t v s . t e t r a v a l e n t , 252 i n s i t u l e a c h m i n i n g , 290-91 i n t e r a c t i o n w i t h reduced m i n e r a l s , 291-95 i s o t h e r m s , 10f l e a c h a b i l i t y from Ralston C r e e k , 283t l e a c h i n g e f f i c i e n c y , 281t m o b i l i t y , 287 n a t u r a l m o b i l i t y , 295 r e c o v e r a b l e , 392 r e l e a s e from R a l s t o n Creek, 271-86 r o l l - f r o n t d e p o s i t s , 288 s o l u b i l i t y v s . E h , 155f s o l u b i l i t y , carbonate g r o u n d w a t e r , 287 s o r p t i o n , 12 s o r p t i o n and d e s o r p t i o n , 1 2 , 1 5 f

uranium—Continued s o u r c e r o c k s , 200 w a s t e s t o r a g e , 162 s o r p t i o n and d e s o r p t i o n i s o t h e r m s , 15f uranium mine, i n s i t u , w e l l p a t t e r n , 292f W Waste f o r m - l e a c h a n t s y s t e m , 356f Waste package components, 67 Water f l o w r a t e s , e f f e c t s on l e a c h i n g , 349-58 X X-ray d i f f r a c t i o n analyses, s u s p e n s i o n s , 144t

neptunium

Ζ Zircon c o m p o s i t i o n dependence, 310 p o l y m o r p h i s m , 313 s t r u c t u r e , 306 Z i r c o n i a pH s e n s o r s c h e m i c a l p u r i t y e f f e c t s , 212 c o n s t r u c t i o n , 203-4 d e s i g n , 205f EMF v s . pH r e s p o n s e , 207f e x p e c t e d r a n g e , 203 pH r e s p o n s e , 2 0 2 , 2 0 4 , 2 0 6 r e s i s t i v i t y measurements, 204 r e s p o n s e , 21 Of y t t r i a c o n t e n t s , 214

Production by Anne Riesberg Indexing by Deborah Corson Jacket design by Anne G. Bigler Elements typeset by Hot Type Ltd., Washington, D.C. Printed and bound by Maple Press Co., York, Pa.