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OCR for page R1
EvnIuntion of the
U.S. Department of Energy's
Alternatives for the
Removal and Disposition
of Molten Salt Reactor
Experiment Fluoride Salts
Molten Salt Panel of the
Committee on Remediation of Buried and Tank Wastes
Board on Radioactive Waste Management
Commission on Geosciences, Environment, and Resources
National Research Council
NATIONAL ACADEMY PRESS
Washington, D.C. 1997
OCR for page R2
NOTICE: The project that is the subject of this report was approved by the
Governing Board of the National Research Council, whose members are drawn
from the councils of the National Academy of Sciences, the National Academy
of Engineering, and the Institute of Medicine. The members of the committee
responsible for the report were chosen for their special competences and with
regard for appropriate balance.
This report has been reviewed by a group other than the authors
according to procedures approved by the Report Review Committee consisting of
members of the National Academy of Sciences, the National Academy of
Engineering, and the Institute of Medicine.
Support for this study was provided by the U.S. Department of Energy
under Grant No. DE-FC01-94EW54069. All opinions, findings, conclusions, or
recommendations expressed herein are those of the authors and do not necessarily
reflect the views of the U.S. Department of Energy.
Library of Congress Catalog Card Number 96-72354
International Standard Book Number 0-309-05684-5
Additional copies of this report are available from:
National Academy Press
2101 Constitution Avenue, N.W.
Box 285
Washington, DC 20055
800-624-6242
202-334-3313 (in the Washington Metropolitan Area)
http://www.nap.edu
Copyright 1997 by the National Academy of Sciences. All rights reserved.
Cover: The cover shows a drawing of one of the drain tanks of the Molten Salt
Reactor Experiment that contains a solidified mixture of radioactive fluoride salts.
The top section, attached to bayonet-like thimbles that penetrate the bottom section,
was designed for cooling water to absorb heat from the tank contents. The
background shows a ternary phase diagram for the three main ingredients of the
fluoride salts—lithium fluoride (LiF), beryllium fluoride (BeF2), and zirconium
fluoride (ZrF41. The dark green color is the true color of solid uranium tetrafluoride
(llF4), also present in the salts. Special thanks to Mary Catlin for digitizing the
figures from Peretz (1996c) for this artwork.
Printed in the United States of America
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MOLTEN SALT PANEL OF THE COMMITTEE ON REMEDIATION OF
BURIED AND TANK WASTES
JOHN L. MARGRAVE, Chair, Rice University, Houston, Texas
SOL BURSTEIN, Wisconsin Electric Power, Milwaukee (retired)
ROBERT J. CATLIN, University of Texas Health Science Center, Houston (retired)
GREGORY R. CHOPPIN, Florida State University, Tallahassee
MELVIN S. COOPS, Lawrence Livermore National Laboratory, California
FLOYD L. CULLER, JR., Electric Power Research Institute, Inc., Palo Alto,
California (emeritus)
ALBERT W. JACHE, Marquette University, Milwaukee, Wisconsin (emeritus)
RONALD KNIEF, Ogden Environmental and Energy Services, Albuquerque,
New Mexico
MILTON LEVENSON, Bechtel International, San Francisco, California (retired)
ROBERT A. PENNEMAN, Los Alamos National Laboratory, New Mexico (retired)
ROBERT A. RAPP, Ohio State University, Columbus (emeritus)
EDWIN L. ZEBROSKI, Aptech Engineering Services, Inc., Sunnyvale, California
Consultants
VALERIE PUTMAN, Lockheed Martin Idaho Technologies Company, Idaho Falls
THOMAS A. REILLY, Westinghouse Savannah River Company, Aiken, South Carolina
NRC*taff
THOMAS E. KIESS, Study Director
REBECCA BURKA, Senior Project Assistant
ERIKA L. WILLIAMS, Project Assistant
. . .
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COMMITTEE ON REMEDIATION OF BURIED AND TANK WASTES
THOMAS M. LESCHINE, Chair, University of Washington, Seattle
DENISE BIERLEY, Roy F. Weston, Albuquerque, New Mexico
ROBERT J. BUDNITZ, Future Resources Associates, Berkeley, California
THOMAS A. BURKE, The Johns Hopkins University, Baltimore, Maryland
ROBERT J. CATLIN, University of Texas, Houston (retired)
GREGORY R. CHOPPIN, Florida State University, Tallahassee
JAMES H. CLARKE, Eckenfelder, Inc., Nashville, Tennessee
THOMAS A. COTTON, JK Research Associates, Inc., Arlington, Virginia
ALLEN G. CROFF, Oak Ridge National Laboratoly, Tennessee
DONALD R. GIBSON, JR., TRW Environmental Safety Systems, Vienna, Virginia
JAMES H. JOHNSON, JR., Howard University, Washington, D.C.
W. HUGH O'RIORDAN, Givens Pursley & Huntley, Boise, Idaho
GLENN PAULSON, Paulson and Cooper, Inc., Jackson Hole, Wyoming
BENJAMIN ROSS, Disposal Safety Incorporated, Washington, D.C.
PAUL A. WITHERSPOON, University of California, Berkeley
RAYMOND G. WYMER, Oak Ridge National Laboratory, Tennessee (retired)
NRC Staff
ROBERT S. ANDREWS, Senior Staff Officer
DENNIS L. DuPREE, Senior Project Assistant
PATRICIA A. JONES, Senior Project Assistant
iv
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BOARD ON R\DlOACTlVE WASTE MANAGEMENT
MICHAEL C. KAVANAUGH, Chair, Malcolm Pirnie, Inc., Oakland, California
B. JOHN GARRICK, Vice-Chair. PLG, Inc., Newport Beach, California
JOHN F. AHEARNE, Sigma Xi, The Scientific Research Society, and Duke University,
Research Triangle Park and Durham, North Carolina
JEAN M. BAHR, University of Wisconsin, Madison
SOL BURSTEIN, Wisconsin Electric Power, Milwaukee (retired)
ANDREW P. CAPUTO, Natural Resources Defense Council, Washington, D.C.
MELVIN W. CARTER, Georgia Institute of Technology, Atlanta (emeritus)
PAUL P. CRAIG, University of California, Davis (emeritus)
MARY R. ENGLISH, The University of Tennessee, Knoxville
DARLEANE C. HOFFMAN, Lawrence Berkeley Laboratory, Berkeley, California
JAMES H. JOHNSON, JR., Howard University, Washington, D.C.
CHARLES McCOMBIE, NAGRA, Wettingen, Switzerland
ROBERT MEYER, Keystone Scientific, Inc., Fort Collins, Colorado
D. WARNER NORTH, Decision Focus, Inc., Mountain View, California
PAUL SLOVIC, Decision Research, Eugene, Oregon
BENJAMIN L. SMITH, Independent Consultant, Columbia, Tennessee
NRC Staff
KEVIN D. CROWLEY, Director
ROBERT S. ANDREWS, Senior Staff Officer
KARYANIL T. THOMAS, Senior Staff Officer
THOMAS E. KIESS, Staff Officer
SUSAN B. MOCKLER, Research Associate
LISA J. CLENDENING, Administrative Associate
ROBIN L. ALLEN, Senior Project Assistant
REBECCA BURKA, Senior Project Assistant
DENNIS L. DuPREE? Senior Project Assistant
PATRICIA A. JONES, Senior Project Assistant
ANGELA R. TAYLOR, Project Assistant
ERIKA L. WILLIAMS, Research Assistant
v
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COMMISSION ON GEOSCIENCES, ENVIRONMENT,
AND RESOURCES
GEORGE M. HORNBERGER, Chair, University of Virginia, Charlottesville
PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania
JAMES P. BRUCE, Canadian Climate Program Board, Ottawa, Ontario
WILLIAM L. FISHER, University of Texas, Austin
JERRY F. FRANKLIN, University of Washington, Seattle
THOMAS E. GRAEDEL, Yale University, New Haven, Connecticut
DEBRA KNOPMAN, Progressive Foundation, Washington, D.C.
KAI N. LEE, Williams College, Williamstown, Massachusetts
PERRY L. McCARTY, Stanford University, California
JUDITH E. McDOWELL, Woods Hole Oceanographic Institution, Massachusetts
RICHARD A. MESERVE, Covington & Burling, Washington, D. C.
S. GEORGE PHILANDER, Princeton University, New Jersey
RAYMOND A. PRICE, Queen's University at Kingston, Ontario
THOMAS C. SCHELLING, University of Maryland, College Park
ELLEN SILBERGELD, University of Maryland Medical School, Baltimore
VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida
E-AN ZEN, University of Maryland, College Park
NRC Staff
STEPHEN RATTIEN, Executive Director
STEPHEN D. PARKER, Associate Executive Director
MORGAN GOPNIK, Assistant Executive Director
GREGORY SYMMES, Reports Officer
JAMES MALLORY, Administrative Officer
SANDI FITZPATRICK, Administrative Associate
MARQUITA SMITH, Administrative Assistant/Technology Analyst
Vl
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Acknowledgments
The pane! is especially appreciative of the support of Dr. Tom
Kiess, Ms. Rebecca Burka, and Ms. Erika Williams in collecting,
assembling, and organizing the input from our group into a coherent
format. We also wish to acknowledge the cooperation of the management
and staff of the Oak Ridge National Laboratory and of the Department of
Energy in providing information for this report. The assistance of Ray
Wymer, a liaison to the panel from the Committee on Remediation of
Buried and Tank Wastes, is gratefully acknowledged.
The early assistance of Dr. lames Zucchetto, Director of the
National Research Council Board on Energy and Environmental Systems,
and Dr. Douglas Raber, Director of the National Research Council Board
on Chemical Science and Technology, is much appreciated.
. .
Vll
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The National Academy of Sciences is a private, nonprofit, self-
perpetuating society of distinguished scholars engaged in scientific and
engineering research, dedicated to the furtherance of science and technology and
to their use for the general welfare. Upon the authority of the charter granted to it
by the Congress in 1863, the Academy has a mandate that requires it to advise
the federal government on scientific and technical matters. Dr. Bruce Alberts is
president of the National Academy of Sciences.
The National Academy of Engineering was established in 1964, under
the charter of the National Academy of Sciences, as a parallel organization of
outstanding engineers. It is autonomous in its administration and in the selection
of its members, sharing with the National Academy of Sciences the responsibility
for advising the federal government. The National Academy of Engineering also
sponsors engineering programs aimed at meeting national needs, encourages
education and research, and recognizes the superior achievements of engineers.
Dr. William A. Wulf is interim president of the National Academy of
. .
_nglneerlng.
The Institute of Medicine was established in 1970 by the National
Academy of Sciences to secure the services of eminent members of appropriate
professions in the examination of policy matters pertaining to the health of the
public. The Institute acts under the responsibility given to the National Academy
of Sciences by its congressional charter to be an adviser to the federal
government and, upon its own initiative, to identify issues of medical care,
research, and education. Dr. Kenneth Shine is president of the Institute of
Medicine.
The National Research Council was organized by the National Academy
of Sciences in 1916 to associate the broad community of science and technology
. .
with the Academy's purposes of furthering knowledge and of advising the federal
government. Functioning in accordance with general policies determined by the
Academy, the Council has become the principal operating agency of both the
National Academy of Sciences and the National Academy of Engineering in
providing services to the government, the public, and the scientific and
engineering communities. The Council is administered jointly by both
Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. William A.
Wulf are the chairman and interim vice-chairman, respectively, of the National
Research Council.
. . .
vail
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Preface
More than 25 years ago, I was a consultant to the group that was
designing, building, and operating the Molten Salt Reactor Experiment
(MSRE). Now the "mothballed" MSRE presents an environmental hazard
that must be remediated soon, and I have been appointed to chair a National
Research Council study of the remediation alternatives under consideration.
The fluoride salts that were once the reactor fuel and that are now stored in
drain tanks have been unstable since the reactor was shut down in 1969.
The potential hazards of the toxic, radioactive, and fissionable materials
have been extensively reviewed since the early 1970s and are worsening
with time.
This report describes the scientific and engineering aspects of
feasible remediation plans for the fluoride salt contents of the three drain
tanks of the facility. The panel has carefully reviewed the previous studies
and the recent technical evaluations of the alternatives proposed by staff at
the Oak Ridge National Laboratory (ORNL). The panel was impressed
with the information and background knowledge available at ORNL and
from other Department of Energy (DOE) sites, including that from retirees
who had run the reactor and who had developed the basic fluoride
chemistry.
At the present time, DOE has provided funding and personnel to
take action on this environmental hazard. Many ORNL staff and now
members of the public recognize the high priority of this remediation
project. The panel supports the completion of remediation work on this
cleanup problem that the present DOE management has inherited and has
the opportunity to solve.
John L. Margrave
Houston, Texas
zx
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Contents
Executive Summary
1 Introduction
Current Status of the MSRE, 15
Role of the National Research Council, 19
Scope and Organization of This Report, 20
2 Radiolysis and Nuclear Reactions
Radioactive Source Terms, 23
Radiation Effects and General Comments, 27
Radiation-Induced Liberation of Fluorine and Uranium
Hexafluoride Gases, 28
Radiation Decomposition of Solid Uranium Hexafluoride, 31
Long-Term Effects of Leaving Plutonium in the Salt After
Uranium Removal, 33
Excess of Reducing Species in the Salt and Hazards of Simple
Remelting, 34
3 Fluoride Salt Chemistry, Partitioning,
and System Corrosion
Chemistry Relevant to the Present Status, 37
Chemical Consequences of RadioTysis, 38
Partitioning of Uranium from the Salt, 39
Plutonium Partitioning by Fluorination, 41
Nonfluorination Option for Plutonium Separation, 42
System Corrosion Issues, 42
Radiation-Tnduced Corrosion Questions, 43
1
10
23
37
4 Preferred Technical Approach 45
Comments on Process Steps, 45
Development of a Preferred Approach, 46
Xl
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. .
X11
Comments on Specific Separation
Technologies
Fluorination, 50
Direct Fluorination, 51
Hydrofluorination, 52
Alternative Fluorinating Agents, 52
Electroref~ning, 53
Distillation of Molten Salt, 54
Aqueous Dissolution and Separation, 54
Criticality Concems in Aqueous Processing, 55
Fluoride Removal, 56
Conclusions on Aqueous Processing, 56
Stabilization Technologies, 57
6 Nuclear Criticality Considerations
Criticality Issues in Processing, 58
Criticality Hazard of Remelting the Fluoride Salts in the Drain
Tanks, 6 1
CONTENTS
50
58
Rationale for Technical Insignificance of a Criticality Excursion, 63
Concluding Comments, 64
7 Strategic Alternatives
Permanent Disposal in the Drain Tanks, 65
Disposal of All Key Contaminants in the Federal Repository, 65
Disposal of Key Contaminants in the Salt Residue in the Waste
Isolation Pilot Plant (WIPP), 66
Disposal of Key Contaminants in Salt Residue in the Federal
Repository, 67
Reuse of the Salt, 68
Interim Storage, 68
Rationale for Rejecting the First Six Alternatives, 69
Interim Versus Permanent Storage and Disposal, 70
Management of MSRE Hazards
Current Hazards, 72
Hazard Management Activities, 74
65
72
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CONTENTS
Crucial Role of Further Activities for Condition and Process
Assessment' 74
Major Recommendation Concerning Hazards, 75
Detailed Recommendations Regarding Hazards, 76
9 Summary and Responses to Questions in Statement
of Task
Technical Summary, 79
Strategy for Remediation, 81
Where is the Uranium? 81
How Can a Condition Assessment Affect Remediation Plans? 82
The Panel's Preferred Alternative, 83
Hazards, 83
Responses to Questions in Statement of Task, 84
Question 1, 84
Question 2, 85
Question 3, 86
Panel Perspective, 87
Overall Conclusion, 88
References
Appendixes
A List of Materials Reviewed
B Alternative Fluorinating Agents
C Contamination Concerns Relating to Radon Gas
Spread
D Use of a Nuclear Poison to Inhibit Nuclear
Criticality
. . .
x~
79
89
A.1
B.1
C.1
D.1
E Hazard Scoping of Major Actions for Remediation E.1
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XIV
F List of Acronyms and Abbreviations
G Glossary
H Biographical Sketches of Molten Salt Pane} Members
and Consultants
CONTENTS
F.1
G.1
H.1
