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OCR for page R1
Technical
B- To ·ve
a..
Mountain
~ - ..~ - .~o
Committee on
Technical Bases for Yucca Mountain Standards
Board on Raclioactive Waste Management
Commission on Geosciences, Environment, anc! Resources
National Research Council
NATIONAL ACADEMY PRESS
Washington, D.C. 1 995
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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 Tom 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 a 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 on Technical Bases for Yucca Mountain
Standards was provicie(i by the U.S. Environmental Protection Agency,
uncler contract number 68D30014.
Library of Congress Catalog Card No. 95-69192
International Standard Book Number 0-309-05289-0
Additional copies of this report are available from:
National Academy Press
2 1 0 1 Constitution Avenue' N. W.
Box 285
Washington, D.C. 20055
Call 800-624-6242 or 202-334-3313 (in the Washington Metropolitan
Area).
B563
Copyright 1995 by the National Academy of Sciences. All rights reserved.
Printed in the United States of America
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COMMITTEE ON TECHNICAL BASES FOR YUCCA
MOUNTAIN STANDARDS
ROBERT W. FRI, Chair, Resources for the Future, Washington, DC,
JOHN F. AHEARNE, Sigma Xi, The Scientific Research Society,
Research Triangle Park, North Carolina
JEAN M. BAHR, University of Wisconsin, Madison
R. DARRYL BANKS, World Resources Institute, Washington, DC
ROBERT J. BUDNITZ, Future Resources Associates, Berkeley,
California
SOL BURSTEIN, Wisconsin Electric Power, Milwaukee (retired)
MELVIN W. CARTER, Georgia Institute of Technology, Atlanta
(professor emeritus)
CHARLES FAIRHURST, University of Minnesota, Minneapolis
CHARLES McCOMBIE, National Cooperative for the Disposal of
Radioactive Waste,Wettingen, Switzerland
FRED M. PHILLIPS, New Mexico Institute of Mining and Technology,
Socorro
THOMAS H. PIGFORD, University of California, Berkeley, Oakland
(professor emeritus)
ARTHUR C. UPTON, New Mexico School of Medicine, Santa Fe
CHRIS G. WHIPPLE, ICE Kaiser Engineers, Oakland, California
GILBERT F. WHITE, University of Colorado, Boulder
SUSAN D. WILTSHIRE, JK Research Associates, Inc., Beverly,
Massachusetts
Staff
MYRON F. UMAN, Study Director
RAYMOND A. WASSEL, Senior Staff Officer
ROBERT J. CROSSGROVE, Copy Editor
LISA J. CLENDEN1NG, Senior Project Assistant
. . .
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BOARD ON RADIOACTIVE WASTE MANAGEMENT
MICHAEL C. KAVANAUGH, Chair, ENVIRON Corporation, Emeryville, California
B. JOHN GARRICK, Vice-Chair, PLG, Incorporated, Newport Beach, California
JOHN F. AHEARNE, Sigma Xi, The Scientific Research Society, Research Triangle
Park, North Carolina
JEAN M. BAHR, University of Wisconsin, Madison
LYNDA L. BROTHERS, Davis Wright Tremaine, Seattle, Washington
SOL BURSTEIN, Wisconsin Electric Power, Milwaukee (retired)
MELVIN W. CARTER, Georgia Institute of Technology, Atlanta (professor emeritus)
PAUL P. CRAIG, University of California, Davis (professor emeritus)
MARY R. ENGLISH, University of Tennessee, Knoxville
ROBERT D. HATCHER, JR., University of Tennessee/Oak Ridge National Laboratory,
Knoxville
DARLEANE C. HOFFMAN, Lawrence Berkeley Laboratory, Berkeley, California
H. ROBERT MEYER, Keystone Scientific, Inc., Fort Collins, Colorado
PERRY L. McCARTY, Stanford University, California
CHARLES McCOMBIE, National Cooperative for the Disposal of Radioactive Waste,
Wettingen, Switzerland
PRISCILLA P. NELSON, Universtiy of Texas at Austin
D. KIRK NORDSTROM, U.S. Geological Survey, Boulder, Colorado
D. WARNER NORTH, Decision Focus, Incorporated, Mountain View, California
GLENN PAULSON, Illinois Institute of Technology, Chicago
PAUL SLOVIC, Decision Research, Eugene, Oregon
BENJAMIN L. SMITH, Independent Consultant, Columbia, Tennessee
Staff
CARL A. ANDERSON, Staff Director
KEVIN D. CROWLEY, Associate Director
ROBERT S. ANDREWS, Senior Staff Officer
K~ARYANIL T. THOMAS, Senior Staff Officer
SUSAN B. MOCKLER, Research Associate
THOMAS KIESS, Staff Officer
ROBIN L. ALLEN, Senior Project Assistant
REBECCA BURKA, Senior Project Assistant
LISA J. CLENDENING, Senior Project Assistant
DENNIS L. DUPREE, Senior Project Assistant
SCOTT A. HASSEL, Project Assistant
PATRICIA A. JONES, Project Assistant
IV
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COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND
RESOURCES
M. GORDON WOLMAN, Chair, The Johns Hopkins University,
Baltimore, Maryland
PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh,
Pennsylvania
EDITH BROWN WEISS, Georgetown University Law Center,
Washington, DC
JAMES P. BRUCE, Canadian Climate Program Board, Ottawa
WILLIAM L. FISHER, University of Texas, Austin
EDWARD A. FRIEMAN, Scripps Institution of Oceanography, La Jolia,
California
GEORGE M. HORNBERGER, University of Virginia, Charlottesville
W. BARCLAY KAMB, California Institute of Technology, Pasadena
PERRY L. McCARTY, Stanford University, California
S. GEORGE PHILANDER, Princeton University, New Jersey
RAYMOND A. PRICE, Queen's University at Kingston, Ontario,
Canada
THOMAS C. SCHELLING, University of Maryland, College Park
ELLEN SILBERGELD, University of Maryland Medical School,
Baltimore, Maryland
STEVEN M. STANLEY, The Johns Hopkins University, Baltimore,
Maryland
VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida
Stay
STEPHEN RATTIEN, Executive Director
STEPHEN D. PARKER, Associate Executive Director
MORGAN GOPNIK, Assistant Executive Director
JAMES E. MALLORY, Administrative Officer
SANDRA S. FITZPATRICK, Administrative Associate
v
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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. Harold Liebowitz is president
of the National Academy of Engineering.
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. Harold Liebowitz are chairman and
vice chairman, respectively, of the National Research Council.
Vl
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PREFACE
In Section 801 of the Energy Policy Act of 1992 (P.L. 102-486),
the U.S. Congress directed the U.S. Environmental Protection Agency
(EPA) to promulgate standards to ensure protection of public health from
high-level radioactive wastes in a deep geologic repository that might be
built under Yucca Mountain in Nevada. By this provision, EPA must set
the standards to ensure protection of the health of individual members of
the public. The standards will apply only to the Yucca Mountain site.
To assist EPA in this endeavor, Congress also asked the National
Academy of Sciences to advise the agency on the technical bases for such
standards. This report contains that advice. It was prepared by a committee
organized under the auspices of the National Research Council, which is
jointly managed by the National Academy of Sciences and the National
Academy of Engineering for the purpose of conducting studies such as this.
Biographical information on the members of our committee is presented in
Appendix A.
Our charge was contained explicitly in Section 801(a)~2) of the Act
and elaborated in the Conference Report accompanying the bill as well as
in correspondence from the Chairman of the Senate Committee on Energy
and Natural Resources, Senator J. Bennett Johnston. These documents are
contained in Appendix B. The charge consisted oftwo parts. The first was
to address three specific questions contained in Section 801 Am. The
second was to advise EPA on the technical basis for the health-based
standards that it is mandated to prepare.
To accomplish both objectives of the charge, we structured our
study to focus on the state of scientific and technical understanding
available for assessing the future behavior of an underground repository and
for devising appropriate standards. We also took account of the eventual
need for the U.S. Department of Energy (DOE) to demonstrate compliance
with the standarcis. In the process, we conducted a series of five open
technical meetings to assure that we had access to all of the analyses,
including those in the international literature, that might pertain to our task.
We invited to these meetings more than 50 nationally and internationally
known scientists and engineers in pertinent fields to discuss the technical
issues with us. At the final open meeting, we received recommendations
from a number of observers about what they hoped would be in our report.
. .
V11
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. . .
V111
YUCCA MOUNTAINSTANDARDS
The information provided by invited experts and public participants has
been most valuable to our work.
The three Federal agencies involved (the U.S. Nuclear Regulatory
Commission (USNRC), in addition to DOE and EPA), state and county
agencies in Nevada, and private organizations, such as the Electric Power
Research Institute all of which have sponsored research on the technical
issues before us generously shared their data and insights with us. We
also retained two consultants, Paul Dejonghe (Nuclear Energy Research
Center, Mol. Belgium (retired)) summarizer! for us the experience of other
countries in setting standards for high-level radioactive waste repositories,
and DetIof von Winterfeldt (University of Southern California, Los
Angeles) reviewed the literature on human intrusion into a repository at
some time in the future and institutional controls to mitigate such
intrusions. All of the information we received is available to the public.
Although we believe that the full range of scientific information
related to the standards was available to us, it became clear in the course of
our work that designing the standards requires making decisions based as
much or more on policy considerations than on science. It is equally clear
that there is no sharp dividing line between science and policy. In
developing this report, we have recognized that the committee members can
speak as experts only on matters of science, but we have not construed our
assignment so narrowly as to limit the usefulness of our recommendations
for standard-setting in the real world. In short, we have commented on
policy issues where we thought it necessary.
Science alone cannot answer policy questions, however, and so we
do not make policy recommendations in this report on the grounds that
there is by definition a limited scientific basis for selecting one policy
alternative over another. We have instead tried to use available technical
information and judgment to suggest a starting point for the rulemaking
process that will lead to a policy decision.
By applying this approach consistently throughout the report, we
have achieved consensus on a number of complex and controversial issues.
In particular, we agree on the answers to the questions posed by Congress,
the technical bases for health-based standards, and most of the elements of
a procedure for assessing compliance with the standards. On one aspect of
the compliance assessment procedure, however, one member of the
committee has prepared a personal statement presented in Appendix E,
outlining where his views diverge from the view of the rest of the
committee. As chair of the committee, I have provided my perspective on
that statement in Appendix F.
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PREFACE
IX
The issue in question concerns what assumptions to make about the
future distribution of individuals that would be exposed to any possible
releases from the repository. Assessing compliance, which would! be
required in any licensing procedure, requires that the populations or
individuals at risk be specified so their exposures or risks can be estimated
and compared with the standards. Because the population at greatest risk
from repository releases will exist far in the future, that population and its
distribution are not amenable to scientific prediction. Developing a
complete exposure scenario for compliance analysis therefore requires
making assumptions about who will be at risk. While scientific information
can be valuable in developing these assumptions, the choice of assumptions
is ultimately a matter for policy judgment.
In the committee's view, there are two avenues for approaching the
construction of exposure scenarios. The two are summarized and compared
in Chapter 3 and described in detail in Appendixes C and D, respectively.
The committee offers these approaches as options for regulators to consider
~ · .
in specifying an exposure scenario.
The personal statement by one
committee member in Appendix E argues that only one of these approaches
is appropriate. Although others may have an equally strong preference for
the other approach, the remainder of the committee has preferred to follow
its consistent practice of not taking a position on policy questions.
On behalf of my colleagues on the committee, I wish to express our
appreciation to all those who provided us with valuable input for our task.
In particular, at our request, several agencies formally designated liaisons
to the committee whose assignments were to assure that we were fully
informed of the data and analyses that were available to their respective
agencies. In turn, through the liaisons, we shared all of the information we
obtained during the course of our work with their agencies. The liaisons
were J. William Gunter, EPA; Margaret Federline, USNRC; Stephen J.
Brocoum, DOE; Les W. Bradshaw, Nye County (Nevada) Nuclear Waste
Repository Program; and Engelbrecht von Tiesenhausen, Clark County,
Nevada. Robert Loux performed a similar function, although informally,
for the State of Nevada Nuclear Waste Projects Office. Rosa Yang made
sure that we were iffily informed of the results of research performed under
the auspices of the Electric Power Research Institute. We are indebted to
these individuals for their dedication to providing us with information.
Finally, our work, while difficult enough, would have been even
more so without the dedicated support ofthe NationalResearch Council
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Cam ~ Worsen Myron Um=, Lisa Clendening, Id oglers who ago
Raised He committee.
Bed W. hi
Chad
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C O N T E N T S
EXECUTIVE SUMMARY
CHAPTER 1 - INTRODUCTION 15
SCOPE OF THE STUDY 18
BACKGROUND AND APPROACH ....................
The Repository System ...........................
Issues to Be Considered in Approaching the Study ......
Large but improbable doses ..................
Demonstration of compliance .................
Fundamental sirs. derived standards .............
Time scale ................................
Choices Affecting the Bases of the Standard ...........
CHAPTER 2 - PROTECTING HUMAN HEALTH ..............
THE HEALTH EFFECTS OF IONIZING RADIATION
DEVELOPMENT OF RADIATION PROTECTION
STANDARDS ..........................
. . .. .. . . - · · .
23
23
27
27
28
29
29
30
33
34
39
General Consensus in Radiation Protection Principles and
Standards 39
THE FORES OF THE STANDARD 41
ELEMENTS OF AN INDIVIDUAL-RISK STANDARD 47
What Level of Protection? 49
Who Is Protected? 49
For HowI`on~? 54
57
58
59
PROTECTING THE GENERAL PUBLIC
PROTECTING THE GLOBAL POPULATION
NEGLIGIBLE INCREMENTAL RISK ..............
PROTECTING LOCAL POPULATIONS . . . .. .. . . .. . . . . . . 61
Population-Risk Standard .........................
Spatial Gradient in Risk ..........................
PREFERRED FORM OF THE STANDARD
CHAPTER 3 - ASSESSING COMPLIANCE
rNTRODUCTION . ....
Xl
61
62
63
67
67
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. .
X11
YUCCA MO UNTAIN STY NDAh1)S
PART I: OVERVIEW OF PERFORMANCE ASSESSMENT
70
Reasonable Confidence 70
Time scale
Probabilistic Analysis of Risk
QUANTITATIVE CALCULATION OF REPOSITORY
PERFORMANCE ...............................
Elements of Performance Assessment ................
71
72
73
74
Conceptual mode! 74
Mathematical mode} 76
76
Numerical analysis
Mode! parameters 76
Bounciary conditions
77
Treatment of Uncertainty 7X
Probabilistic modeling 78
Bounding estimates 79
Alternative conceptual models 79
80
Summary
PATHWAYS AND PROCESSES FOR PERFORMANCE
ASSESSMENT AT YUCCA MOUNTAIN
PART II: EARTH SCIENCE AND ENGINEERING FACTORS
IN PERFORMANCE ASSESSMENT AT YUCCA
MOUNTAIN 85
Release from the waste form 85
81
Transport from canisters to the near-field unsaturated
zone ................................
Gas phase transport from the unsaturated zone to the
86
atmosphere above Yucca Mountain 87
Atmospheric circulation leading to dispersal of
gaseous radionuclides in the world atmosphere
88
Aqueous phase transport from the unsaturated zone to
the water table 88
Saturated zone transport from the aquifer beneath the
repository to other locations from which water
may be extracted by humans or ultimately reach
the surface in a regional discharge area
Grn~l'~1 ~nr1 Fni~n(lic, N~tl~rn1 Morlif;er~
Climate change
Seismicity . . .
90
91
91
92
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TABLE OF CONTENTS
Volcanism .
. . .
XIZI
94
PART III: EXPOSURE SCENARIOS rN PERFORMANCE
ASSESSMENT 95
Selection of Exposure Scenarios for Performance
Assessment Calculations 97
Exclusion Zone 103
CHAPTER 4 - HUMAN INTRUSION AND INSTITUTIONAL
CONTROLS .......................................
ENTRODUCTION ..................................
The Consequences of Intrusion ....................
Technical basis ...........................
Consequence-based analysis ...........
105
105
109
110
111
ADDITIONAL BASES FOR OUR RECOMMENDATION . . 1 13
Categories of Future Human Intrusion Events 1 14
Categories of Hazards Resulting From an Intrusion . . . 1 14
CHAPTER 5 - IMPLICATIONS OF OUR CONCLUSIONS
COMPARISON WITH 40 CFR 191 ....................
Considerations
Generic vs. site-specific standards .............
Dose vs. risk .............................
Differences From 40 CFR 191
117
117
118
118
118
119
Time period 1 19
Population health effects and release limits 120
Human intrusion 120
.................... 121
............... 121
122
122
122
123
123
124
125
125
126
Ground-water protection
Common Elements With 40 CFR 191
Dose apportionment .......................
R~f~r~nr~hin~nh~re
4~_~_. _.,__ va~v~_^ _ .. . . . . . . . .. . ... . . . . .. . .
Exclusion zone ...........................
Use of mean values ........................
LIMITS OF THE SCIENTIFIC BASIS
TECHNOLOGY-BASED STANDARDS
The Al AD ~ PrinrinlP
1 11~ ~l~f11~ 1 1 Il1~ ..........................
10 CFR 60 ........................................
Minimum Early Release .........................
ADMINISTRATIVE CONSEQUENCES FOR EPA, USNRC,
AND DOE ...................................
127
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XIV
YUCCA M O UNTAIN STA NDAh1)S
APPENDIX A - BIOGRAPHICAL INFORMATION ON COMMITTEE
MEMBERS 129
APPENDW B - CONGRESSIONAL MANDATE FOR
THIS REPORT ...................................
APPENDIX C - A PROBABILISTIC CRITICAL GROUP
APPENDIX D - THE SUBSISTENCE-FARMER
CRITICAL GROUP ...................
1
135
145
153
APPENDIX E - PERSONAL SUPPLEMENTARY STATEMENT
OF THOMAS H. PIGFORD 161
REFERENCES FOR APPENDIX E 182
APPENDIX F - THE COMMITTEE CHAIR'S PERSPECTIVE ON
APPENDIX E 187
GLOSSARY . .
REFERENCES .
....... 189
199
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TABLE OF CONTENTS
List of Figures
Figure 1.1 Map showing location of Yucca Mountain region
adjacent to the Nevada Test Site in southern Nevada.
Figure 1.2 Schematic cross section of the potential Yucca Mountain
repository region showing location of the repository
horizon and static water table with respect to the
thermal/mechanical stratigraphic units
Figure 3.1 The Basic Steps in Performance Assessment
xv
24
....... 25
....... 74
Figure 3.2 Schematic illustration of the major pathways from a
repository at Yucca Mountain to humans 82
List of Tables
Table 2-1
Average Amounts of Ionizing Radiation Received
Yearly by a Member of the U.S. Population .....
... 38
Table 2-2 Estimated Frequencies of Radiation-Induced Fatal
Cancers, Nonfatal Cancers, and Severe Hereditary
Disorders, Weighted for the Severity of their Impacts on
Affected Individuals
...... 39
Table 2-3 Quantitative High-Level Waste Disposal
Objectives/Criteria at International Level and in OECD
Countries
............. 43
Table 2-4 Comparison of the Annual Individual Risks Associated
with USNRC and EPA Standards 50
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