[Federal Register: October 15, 2008 (Volume 73, Number 200)]
[Rules and Regulations]
[Page 61255-61289]
[DOCID:fr15oc08-29]

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Part III

Environmental Protection Agency

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40 CFR Part 197

Public Health and Environmental Radiation Protection Standards for
Yucca Mountain, Nevada; Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 197

[EPA-HQ-OAR-2005-0083; FRL-8724-9]
RIN 2060-AN15

Public Health and Environmental Radiation Protection Standards
for Yucca Mountain, Nevada

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: We, the Environmental Protection Agency (EPA), are
promulgating amendments to our public health and safety standards for
radioactive material stored or disposed of in the potential repository
at Yucca Mountain, Nevada. Congress directed us to develop these
standards and required us to contract with the National Academy of
Sciences (NAS) to conduct a study to provide findings and
recommendations on reasonable standards for protection of the public
health and safety. The health and safety standards promulgated by EPA
are to be ``based upon and consistent with'' the findings and
recommendations of NAS. Originally, these standards were promulgated on
June 13, 2001 (66 FR 32074) (the 2001 standards).
    On July 9, 2004, the U.S. Court of Appeals for the District of
Columbia Circuit vacated portions of the 2001 standards concerning the
period of time for which compliance must be demonstrated. The Court
ruled that the compliance period of 10,000 years was not ``based upon
and consistent with'' the findings and recommendations of the NAS and
remanded those portions of the standards to EPA for revision. These
remanded provisions are the subject of this action.
    This final rule incorporates compliance criteria applicable at
different times for protection of individuals and in circumstances
involving human intrusion into the repository. Compliance will be
judged against a standard of 150 microsieverts per year ([mu]Sv/yr) (15
millirem per year (mrem/yr)) committed effective dose equivalent (CEDE)
at times up to 10,000 years after disposal and against a standard of 1
millisievert per year (mSv/yr) (100 mrem/yr) CEDE at times after 10,000
years and up to 1 million years after disposal. This final rule also
includes several supporting provisions affecting the projections of
expected disposal system performance prepared by the Department of
Energy (DOE).

DATES: Effective Date: This final rule is effective on November 14,
2008.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2005-0083. All documents in the docket are listed on the
http://www.regulations.gov Web site. Although listed in the index, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
electronically through http://www.regulations.gov, for purchase or
access from sources identified in the docket (Docket Nos. EPA-HQ-OAR-
2005-0083-0086 and EPA-HQ-OAR-2005-0083-0087), or in hard copy at the
Air and Radiation Docket, EPA/DC, EPA Headquarters West Building, Room
3334, 1301 Constitution Ave., NW., Washington, DC. The Public Reading
Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday,
excluding legal holidays. The telephone number for the Air and
Radiation Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Ray Clark, Office of Radiation and
Indoor Air, Radiation Protection Division (6608J), U.S. Environmental
Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460-
0001; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; e-mail
address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

I. General Information

A. Does This Action Apply to Me?

    DOE is the only entity regulated by these standards. Our standards
affect NRC only to the extent that, under Section 801(b) of the EnPA,
42 U.S.C. 10141 n., NRC must modify its licensing requirements, as
necessary, to make them consistent with our final standards. Before it
may construct the repository or accept waste at the Yucca Mountain site
and eventually close the repository, DOE must obtain authorization for
these activities from NRC. DOE will be subject to NRC's modified
regulations, which NRC will implement through its licensing
proceedings.

B. How Can I View Items in the Docket?

    1. Information Files. EPA is working with the Lied Library at the
University of Nevada-Las Vegas (http://www.library.unlv.edu/about/
hours.html) and the Amargosa Valley, Nevada public library (http://
www.amargosalibrary.com) to provide information files on this
rulemaking. These files are not legal dockets; however, every effort
will be made to put the same material in them as in the official public
docket in Washington, DC. The Lied Library information file is at the
Research and Information Desk, Government Publications Section (702-
895-2200). Hours vary based upon the academic calendar, so we suggest
that you call ahead to be certain that the library will be open at the
time you wish to visit. The other information file is in the Public
Library at 829 East Farm Road in Amargosa Valley, Nevada (phone 775-
372-5340). As of the date of publication, the hours are Monday and
Thursday (9 a.m.-7 p.m.); Tuesday, Wednesday, and Friday (9 a.m.-5
p.m.); and Saturday (9 a.m.-1 p.m.). The library is closed on Sunday.
These hours can change, so we suggest that you call ahead to be certain
when the library will be open.
    2. Electronic Access. An electronic version of the public docket is
available through the Federal Docket Management System at http://
www.regulations.gov. You may use http://www.regulations.gov to view
comments, access the index listing of the contents of the official
public docket, and to access those documents in the public docket that
are available electronically. To access the docket go directly to
http://www.regulations.gov and select ``Advanced Docket Search'' under
``More Search Options.'' In the Docket ID window, type in the docket
identification number EPA-HQ-OAR-2005-0083 and click on ``Submit.''
Please be patient since the search could take several minutes. This
will bring you to the ``Docket Search Results'' page. From there, you
may access the docket contents (e.g., EPA-HQ-OAR-2005-0083-0002) by
clicking on the icon in the ``Views'' column.

C. Can I Access Information by Telephone or Via the Internet?

    Yes. You may call our toll-free information line<PHONE_NUMBER>) 24
hours per day. By calling this number, you may listen to a brief update
describing our rulemaking activities for Yucca Mountain, leave a
message requesting that we add your name and address to the Yucca
Mountain mailing list, or request that an EPA staff person return your
call. In addition, we have established an electronic listserv through
which you can receive electronic updates of activities related to this
rulemaking. To subscribe to the listserv, go to https://lists.epa.gov/
read/

all_forums. In the alphabetical list, locate ``yucca-updates'' and
select ``subscribe'' at the far right of the screen. You will be asked
to provide your e-mail address and choose a password. You also can find
information and documents relevant to this rulemaking on the World Wide
Web at http://www.epa.gov/radiation/yucca. The proposed rule for
today's final rule appeared in the Federal Register on August 22, 2005
(70 FR 49014). We also recommend that you examine the preamble and
regulatory language for the earlier proposed and final rules, which
appeared in the Federal Register on August 27, 1999 (64 FR 46976) and
June 13, 2001 (66 FR 32074), respectively.

D. What Documents are Referenced in This Final Rule?

    We refer to a number of documents that provide supporting
information for our Yucca Mountain standards. All documents relied upon
by EPA in regulatory decision-making may be found in our docket (EPA-
HQ-OAR-2005-0083). Other documents, e.g., statutes, regulations, and
proposed rules, are readily available from public sources. The
documents below are referenced most frequently in today's final rule.
    Item No. (EPA-HQ-OAR-2005-0083-xxxx).
    0076 Technical Bases for Yucca Mountain Standards (the NAS Report),
National Research Council, National Academy Press, 1995.
    0086 DOE Final Environmental Impact Statement, DOE/EIS-0250,
February 2002.
    0383 ``Geological Disposal of Radioactive Waste,'' International
Atomic Energy Agency Final Safety Requirements (WS-R-4), 2006.
    0417 ``Radiation Protection Recommendations as Applied to the
Disposal of Long-Lived Solid Radioactive Waste,'' International
Commission on Radiological Protection Publication 81, 2000.
    0408 ``Regulating the Long-Term Safety of Geological Disposal:
Towards a Common Understanding of the Main Objectives and Bases of
Safety Criteria,'' OECD Nuclear Energy Agency, NEA-6182, 2007.
    0421 ``1990 Recommendations of the International Commission on
Radiological Protection,'' ICRP Publication 60.
    0423 ``2007 Recommendations of the International Commission on
Radiological Protection,'' ICRP Publication 103.
    0431 Response to Comments Document for Final Rule, EPA-402-R-08-
008, June 2007.

Acronyms and Abbreviations

    We use many acronyms and abbreviations in this document. These
include:

BID--background information document
CED--committed effective dose
CEDE--committed effective dose equivalent
CFR--Code of Federal Regulations
DOE--U.S. Department of Energy
EIS--Environmental Impact Statement
EnPA--Energy Policy Act of 1992
EPA--U.S. Environmental Protection Agency
FEIS--Final Environmental Impact Statement
FEPs--features, events, and processes
FR--Federal Register
GCD--greater confinement disposal
HLW--high-level radioactive waste
IAEA--International Atomic Energy Agency
ICRP--International Commission on Radiological Protection
NAS--National Academy of Sciences
NEA--Nuclear Energy Agency
NEI--Nuclear Energy Institute
NRC--U.S. Nuclear Regulatory Commission
NRDC--Natural Resources Defense Council
NTS--Nevada Test Site
NTTAA--National Technology Transfer and Advancement Act
NWPA--Nuclear Waste Policy Act of 1982, as amended
NWPAA--Nuclear Waste Policy Amendments Act of 1987
OECD--Organization for Economic Cooperation and Development
OMB--Office of Management and Budget
RMEI--reasonably maximally exposed individual
SSI--Swedish Radiation Protection Authority
SNF--spent nuclear fuel
TRU--transuranic
UK--United Kingdom
UMRA--Unfunded Mandates Reform Act of 1995
U.S.C.--United States Code
WIPP LWA--Waste Isolation Pilot Plant Land Withdrawal Act of 1992

Outline of This Action

I. What Is the History of This Action?
    A. Promulgation of 40 CFR Part 197 in 2001
    B. Legal Challenges to 40 CFR Part 197
II. Summary of Proposed Amendments to 40 CFR Part 197 and Public
Comments
    A. How Did We Propose To Amend Our 2001 Standards?
    B. What Factors Did We Consider in Developing Our Proposal?
    C. In Making Our Decisions, How Did We Incorporate Public
Comments on the Proposed Rule?
    D. What Public Comments Did We Receive?
III. What Final Amendments Are We Issuing With This Action?
    A. What Dose Standards Will Apply?
    1. What Is the Dose Standard Between 10,000 Years and 1 Million
Years?
    2. What Is the Dose Standard for 10,000 Years After Disposal?
    3. How Does Our Final Rule Protect Public Health and Safety?
    4. How Did We Consider Uncertainty and Reasonable Expectation?
    5. How Did We Consider Background Radiation in Developing the
Peak Dose Standard?
    6. How Does Our Rule Protect Future Generations?
    7. What is Geologic Stability and Why Is it Important?
    8. Why Is the Period of Geologic Stability 1 Million Years?
    9. How Will NRC Judge Compliance?
    10. How Will DOE Calculate the Dose?
    B. How Will This Final Rule Affect DOE's Performance
Assessments?
IV. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health & Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-income
Populations
    K. Congressional Review Act

I. What Is the History of This Action?

    Radioactive wastes result from the use of nuclear fuel and other
radioactive materials. Today, we are revising certain standards
pertaining to spent nuclear fuel, high-level radioactive waste, and
other radioactive waste (we refer to these items collectively as
``radioactive materials'' or ``waste'') that may be stored or disposed
of in the Yucca Mountain repository. When we discuss storage or
disposal in this document in reference to Yucca Mountain, we note that,
while Public Law 107-200 approved the site at Yucca Mountain for the
development of a repository for the disposal of spent nuclear fuel and
high-level radioactive waste, no licensing decision has been made
regarding the acceptability of the proposed Yucca Mountain facility for
storage or disposal as of the date of this publication. To save space
and to avoid excessive repetition, we will not describe Yucca Mountain
as a ``potential'' repository; however, we intend this meaning to
apply.
    Once nuclear reactions have consumed a certain percentage of the
uranium or other fissionable material in nuclear reactor fuel, the fuel
no longer is useful for its intended purpose. It

then is known as ``spent'' nuclear fuel (SNF). It is possible to
recover specific radionuclides from SNF through ``reprocessing,'' which
is a process that dissolves the SNF, thus separating the radionuclides
from one another. Radionuclides not recovered through reprocessing
become part of the acidic liquid wastes that the Department of Energy
(DOE) plans to convert into various types of solid materials. High-
level radioactive waste (HLW) is the highly radioactive liquid or solid
wastes that result from reprocessing SNF. The SNF that does not undergo
reprocessing prior to disposal remains inside the fuel assembly and
becomes the final waste form for disposal in the repository.
    In the United States, SNF and HLW have been produced since the
1940s, mainly as a result of commercial power production and national
defense activities. Since the inception of the nuclear age, the proper
disposal of these wastes has been the responsibility of the Federal
government. The Nuclear Waste Policy Act of 1982, as amended (NWPA, 42
U.S.C. Chapter 108) sets forth the framework for the disposal of SNF
and HLW. In general, DOE is responsible for siting, constructing, and
operating an underground geologic repository for the disposal of SNF
and HLW and the Nuclear Regulatory Commission (NRC) is responsible for
licensing the construction and operation of this repository, including
permanent closure and decommissioning of the surface facilities. In
making this licensing decision for the Yucca Mountain repository, NRC
must utilize radiation protection standards that EPA establishes
pursuant to section 801(a) of the Energy Policy Act of 1992 (EnPA, Pub.
L. 102-486).\1\ Thus, today we are promulgating amendments to our
public health protection standards at 40 CFR part 197 (which, pursuant
to EnPA section 801(a), apply only to releases of radioactive material
stored or disposed of at the Yucca Mountain site, rather than generally
applicable). NRC will amend its regulations to be consistent with these
standards.
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    \1\ EnPA, Public Law No. 102-486, 102 Stat. 2776, 42 U.S.C.
10141 n. (1994).
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    On June 3, 2008, pursuant to the NWPA, as amended, DOE submitted a
license application to NRC seeking a license to construct the
repository. NRC will determine whether DOE has met NRC's requirements,
including those implementing 40 CFR part 197, and whether to grant or
deny authorization to construct the repository and a license to receive
radioactive material at the Yucca Mountain site.
    In 1985, we established generic standards for the management,
storage, and disposal of SNF, HLW, and transuranic (TRU) radioactive
waste (see 40 CFR part 191, 50 FR 38066, September 19, 1985), which
were intended to apply to facilities utilized for the storage or
disposal of these wastes, including Yucca Mountain. In 1987, the U.S.
Court of Appeals for the First Circuit remanded the disposal standards
in 40 CFR part 191 (NRDC v. EPA, 824 F.2d 1258 (1st Cir. 1987)). We
later amended and reissued those standards to address issues that the
court raised. Also in 1987, the Nuclear Waste Policy Amendments Act
(NWPAA, Pub. L. 100-203) amended the NWPA by, among other actions,
selecting Yucca Mountain, Nevada, as the only potential site that DOE
should characterize for a geologic repository for SNF and HLW. In
October 1992, Congress enacted the EnPA and the Waste Isolation Pilot
Plant Land Withdrawal Act (WIPP LWA, Pub. L. 102-579). These statutes
changed our obligations concerning radiation standards for the Yucca
Mountain candidate repository. The WIPP LWA:
    (1) Reinstated the 40 CFR part 191 disposal standards, except those
portions that were the specific subject of the remand by the First
Circuit;
    (2) Required us to issue standards to replace the portion of the
challenged standards remanded by the court; and
    (3) Exempted the Yucca Mountain site from the 40 CFR part 191
disposal standards.

We issued the amended 40 CFR part 191 disposal standards, which
addressed the judicial remand, on December 20, 1993 (58 FR 66398).
    The EnPA set forth our responsibilities as they relate to Yucca
Mountain and directed us to set public health and safety radiation
standards for Yucca Mountain. Specifically, section 801(a)(1) of the
EnPA directed us to ``promulgate, by rule, public health and safety
standards for the protection of the public from releases from
radioactive materials stored or disposed of in the repository at the
Yucca Mountain site.'' Section 801(a)(2) directed us to contract with
the National Academy of Sciences (NAS) to conduct a study to provide us
with its findings and recommendations on reasonable standards for
protection of public health and safety from releases from the Yucca
Mountain disposal system. Moreover, it provided that our standards
shall be the only such standards applicable to the Yucca Mountain site
and are to be based upon and consistent with NAS's findings and
recommendations. On August 1, 1995, NAS released its report,
``Technical Bases for Yucca Mountain Standards'' (the NAS Report)
(Docket No. EPA-HQ-OAR-2005-0083-0076).

A. Promulgation of 40 CFR Part 197 in 2001

    Pursuant to the EnPA, we developed standards specifically
applicable to releases from radioactive material stored or disposed of
in the Yucca Mountain repository. In doing so, we considered the NAS
Report, our generic standards in 40 CFR part 191, and other relevant
information, precedents, and analyses.
    We evaluated 40 CFR part 191 because those standards were developed
to apply to sites selected for storage and disposal of SNF and HLW.
Thus, we believed that 40 CFR part 191 already included the major
components of standards needed for any specific site, such as Yucca
Mountain. However, we recognized that all the components would not
necessarily be directly transferable to the situation at Yucca
Mountain, and that some modification might be necessary. We also
considered that some components of the generic standards would not be
carried into site-specific standards, since not all of the conditions
found among all potential sites are present at Yucca Mountain. See 66
FR 32076-32078, June 13, 2001 (Docket No. EPA-HQ-OAR-2005-0083-0042),
for a more detailed discussion of the role of 40 CFR part 191 in
developing 40 CFR part 197.
    We also considered the findings and recommendations of the NAS in
developing standards for Yucca Mountain. In some cases, provisions of
40 CFR part 191 were already consistent with NAS's analysis (e.g.,
level of protection for the individual). In other cases, we used the
NAS Report to modify or draw out parts of 40 CFR part 191 to apply more
directly to Yucca Mountain (e.g., the stylized drilling scenario for
human intrusion). See the NAS Report for a complete description of
findings and recommendations (Docket No. EPA-HQ-OAR-2005-0083-0076).
    Because our standards are intended to apply specifically to the
Yucca Mountain disposal system, we tailored our approach to consider
the characteristics of the site and the local populations. Yucca
Mountain is in southwestern Nevada approximately 100 miles northwest of
Las Vegas. The eastern part of the site is on the Nevada Test Site
(NTS). The northwestern part of the site is on the Nevada Test and
Training Range (referred to in our proposal as the Nellis Air Force
Range). The southwestern part of the site is on Bureau of Land
Management land. The

area has a desert climate with topography typical of the Basin and
Range province. Yucca Mountain is made of layers of ashfalls from
volcanic eruptions that happened more than 10 million years ago. There
are two major aquifers beneath Yucca Mountain. Regional ground water in
the vicinity of Yucca Mountain is believed to flow generally in a
south-southeasterly direction. For more detailed descriptions of Yucca
Mountain's geologic and hydrologic characteristics, and the disposal
system, please see Chapter 7 of the 2001 Background Information
Document (BID) (Docket No. EPA-HQ-OAR-2005-0083-0050) and the preamble
to the proposed rule (64 FR 46979-46980, August 27, 1999, Docket No.
EPA-HQ-OAR-2005-0083-0041).
    We proposed the original standards for Yucca Mountain on August 27,
1999 (64 FR 46976). In response to our proposal, we received more than
800 public comments and conducted four public hearings. After
evaluating public comments, we issued final standards (66 FR 32074,
June 13, 2001). See the Response to Comments document from that
rulemaking for more discussion of comments (Docket No. EPA-HQ-OAR-2005-
0083-0043).
    The final standards issued in 2001 as 40 CFR part 197 included the
following:
     A standard to protect the public during management and
storage operations on the Yucca Mountain site;
     An individual-protection standard to protect the public
from releases from the undisturbed disposal system;
     A human-intrusion standard to protect the public after
disposal from releases caused by a drilling penetration into the
repository;
     A set of standards to protect ground water from
radionuclide contamination caused by releases from the disposal system;
     The requirement that compliance with the disposal
standards be shown for 10,000 years;
     The requirement that DOE continue its projections for the
individual-protection and human-intrusion standards beyond 10,000 years
to the time of peak (maximum) dose, and place those projections in the
Environmental Impact Statement (EIS) for Yucca Mountain;
     The concept of the Reasonably Maximally Exposed Individual
(RMEI), defined as a hypothetical person whose lifestyle is
representative of the local population living today in the Town of
Amargosa Valley, as the individual against whom the disposal standards
should be assessed; and
     The concept of a ``controlled area,'' defined as an area
immediately surrounding the repository whose geology is considered part
of the natural barrier component of the overall disposal system, and
inside of which radioactive releases are not regulated.
    More detail on these aspects of the 2001 final rule may be found at
66 FR 32074-32134, June 13, 2001, and 70 FR 49019-49020, August 22,
2005.

B. Legal Challenges to 40 CFR Part 197

    Various aspects of our standards were challenged in lawsuits filed
with the U.S. Court of Appeals for the District of Columbia Circuit in
July 2001. These challenges and the Court's subsequent ruling are
described briefly here, emphasizing the aspects leading to today's
final rule, and in more detail in the preamble to the proposed rule (70
FR 49014, August 22, 2005).
    The State of Nevada, the Natural Resources Defense Council (NRDC),
and several other petitioners challenged various aspects of our final
standards on the grounds that they were insufficiently protective and
had not been adequately justified. The focus of this challenge was the
10,000-year compliance period. Nevada and NRDC claimed that EPA's
promulgation of numerical standards that applied for 10,000 years after
disposal violated the EnPA because such standards were not ``based upon
and consistent with'' the findings and recommendations of the NAS. NAS
recommended standards that would apply to the time of maximum risk,
within the limits imposed by the long-term geologic stability of the
site, and stated that there is ``no scientific basis for limiting the
time period of the individual-risk standard to 10,000 years or any
other value.'' (NAS Report p. 55) The Nuclear Energy Institute (NEI)
challenged the ground-water protection standards as unnecessary to
protect public health and safety, contrary to recommendations of the
NAS, and outside our authority under the EnPA.
    The DC Circuit Court's July 9, 2004 decision dismissed NEI's
challenge, and all of the challenges by Nevada and NRDC, except one. On
the question of EPA's 10,000-year compliance period, the Court upheld
the challenge, ruling that EPA's action was not ``based upon and
consistent with'' the NAS Report, and that EPA had not sufficiently
justified on policy grounds its decision to apply compliance standards
only to the first 10,000 years after disposal. Nuclear Energy Institute
v. Environmental Protection Agency, 373 F.3d 1251 (D.C. Cir. 2004) (NEI
).
    The Court concluded that ``we vacate 40 CFR part 197 to the extent
that it incorporates a 10,000-year compliance period * * *.'' (Id. at
1315) The Court did not address the protectiveness of the 150 [mu]Sv/yr
(15 mrem/yr) dose standard applied over the 10,000-year compliance
period, nor was the protectiveness of the 15 mrem/yr standard
challenged. It ruled only that the compliance period was not consistent
with or based upon the NAS findings and recommendations and, therefore,
was contrary to the plain language of the EnPA.
    As the Court noted, NAS stated that it had found ``no scientific
basis for limiting the time period of the individual-risk standard to
10,000 years or any other value,'' and that ``compliance assessment is
feasible * * * on the time scale of the long-term stability of the
fundamental geologic regime--a time scale that is on the order of
106 years at Yucca Mountain.'' As a result, and given that
``at least some potentially important exposures might not occur until
after several hundred thousand years * * * we recommend that compliance
assessment be conducted for the time when the greatest risk occurs.''
(NAS Report pp. 6-7) Today's action addresses this recommendation and
the DC Circuit ruling.

II. Summary of Proposed Amendments to 40 CFR Part 197 and Public
Comments

    The primary goal of our proposal issued in 2005 was to gather
public comment on the appropriate response to the Court decision and
NAS recommendation to assess compliance at the time of maximum dose
(risk). Therefore, our proposed amendments centered on extending the
compliance period to capture the peak projected dose from the Yucca
Mountain disposal system ``within the limits imposed by the long-term
stability of the geologic environment.'' (NAS Report p. 2) Of course,
establishing a radiological protection standard to apply at the time of
peak dose is a uniquely challenging task. Only a small number of
countries have established standards of any kind for the geologic
disposal of SNF and HLW. Of these, only Switzerland has established a
quantitative standard applicable for as long as 1 million years,
although we are aware that other regulatory bodies outside the U.S. are
contemplating the need to establish some type of regulation addressing
these extremely long time frames. Comments received in the course of
this rulemaking have been helpful given the extraordinary technical
complexity of this task.

A. How Did We Propose To Amend Our 2001 Standards?

    We considered carefully the language and reasoning of the Court's
decision in revising our 2001 standards. As originally promulgated in
2001, 40 CFR part 197 contained four sets of standards against which
compliance would be assessed. The storage standard applies to exposures
of the general public during the operational period, when waste is
received at the Yucca Mountain site, handled in preparation for
emplacement in the repository, emplaced in the repository, and stored
in the repository until final closure. The three disposal standards
apply to releases of radionuclides from the disposal system after final
closure, and include an individual-protection standard, a human-
intrusion standard, and a set of ground-water protection standards.
    The Court's ruling vacated only one aspect of 40 CFR part 197: The
10,000-year compliance period applicable to the disposal standards.
Therefore, the storage standard, which is applicable only for the
period before disposal, is not affected by the ruling. Further, the
Court recognized that the ground-water protection standards were issued
as an expression of EPA's overall ground-water protection policies and
were not among the standards addressed by the NAS, either in form or
purpose (``NAS treated the compliance-period and ground-water issues
quite differently * * * NAS made no `finding' or `recommendation' that
EPA's regulation could fail to be `based upon and consistent with' ''
(NEI, 373 F.3d at 1282)). Therefore, we concluded that the Court's
vacature of the 10,000-year compliance period, which was explicitly
tied to recommendations concerning the individual-protection standard,
does not extend to the ground-water provisions. As a result, we did not
propose to amend the ground-water protection standards. Nothing in
today's final rule affects those standards.
    We proposed to revise only the individual-protection and human-
intrusion standards, along with certain supporting provisions related
to the way DOE must consider features, events, and processes (FEPs) in
its compliance analyses (70 FR 49014, August 22, 2005). In addition, we
proposed to adopt updated scientific factors for calculating doses to
show compliance with the storage, individual-protection, and human-
intrusion standards. We requested comments only on those aspects of the
individual-protection and human-intrusion standards which were to be
amended. Specifically, we proposed to:
     Extend the compliance period for the individual-protection
and human-intrusion standards to 1 million years after disposal
(closure), consistent with NAS estimates regarding the ``long-term
stability of the geologic environment'';
     Retain the dose standard of 150 [mu]Sv/yr (hereafter, 15
mrem/yr) committed effective dose equivalent (CEDE) for the first
10,000 years after disposal, as promulgated in 2001;
     Establish a dose standard of 3.5 mSv/yr (hereafter, 350
mrem/yr) CEDE for the period between 10,000 years and 1 million years;
     Clarify that the arithmetic mean of the distribution of
projected results will be compared to the dose standard for the initial
10,000 years, and specify use of the median of the distribution of
projected results between 10,000 and 1 million years;
     Retain the probability threshold (1 in 10,000 chance of
occurring in 10,000 years, or 1 in 100 million chance of occurring per
year) below which ``very unlikely'' FEPs may be excluded from
consideration;
     Allow FEPs with a probability of occurring above the
probability threshold to be excluded if they would not significantly
affect the results of performance assessments in the initial 10,000
years;
     Require consideration of seismic and igneous events
causing direct damage to the engineered barrier system during the 1
million-year period;
     Require consideration of the effects of increased water
flow through the repository resulting from climate change, which could
be represented by constant conditions between 10,000 and 1 million
years;
     Require consideration of the effects of general corrosion
of the engineered barriers between 10,000 and 1 million years; and
     Require use of updated scientific factors, based on
Publications 60 and 72 of the International Commission on Radiation
Protection (ICRP), to calculate dose for comparison with the storage,
individual-protection, and human-intrusion standards.

B. What Factors Did We Consider in Developing Our Proposal?

    Of great concern in extending the compliance period to 1 million
years is the increasing uncertainty associated with numerical
projections of radionuclide releases from the Yucca Mountain disposal
system and subsequent exposures incurred by the Reasonably Maximally
Exposed Individual (RMEI). This uncertainty affects not only the
projections themselves, but also the interpretation of the results.
There is general agreement in the international community that dose
projections over periods as long as 1 million years cannot be viewed in
the same context or with the same confidence as projections for periods
as ``short'' as 10,000 years. As a result, the nature of regulatory
decision-making fundamentally changes when faced with the prospect of
compliance projections for the next 1 million years. International
guidance from the International Atomic Energy Agency (IAEA) and Nuclear
Energy Agency (NEA), as well as geologic disposal programs in other
countries, recognize this difficulty and accommodate it by viewing
longer-term projections in a more qualitative manner, to be balanced
and supplemented by other considerations that would provide confidence
in the long-term safety of the disposal system. In effect, numerical
dose projections are given less weight in decision-making at longer
times.\2\ Such approaches discourage comparison of projections against
a strict compliance limit.
---------------------------------------------------------------------------

    \2\ For example, the ICRP's most recent recommendations note
that ``both the individual doses and the size of the exposed
population become increasingly uncertain as time increases. The
Commission is of the opinion that in the decision-making process,
owing to the increasing uncertainties, giving less weight to very
low doses and to doses received in the distant future could be
considered.'' (Publication 103, 2007, Docket No. EPA-HQ-OAR-2005-
0083-0423, Paragraph 222)
---------------------------------------------------------------------------

    This uncertainty was the overriding reason for limiting the
compliance period to 10,000 years in our 2001 rule. We supplemented
that 10,000-year compliance period by requiring DOE to continue
projections through the time of peak dose, consistent with the approach
favored by the international community. However, while we believed this
approach was consistent with the NAS recommendation to assess
compliance at the time of maximum dose (risk) and the committee's
acknowledgment that policy considerations would also play a role in
determining the compliance period, the Court concluded that it was
inconsistent with the NAS recommendation. We concluded that the most
direct way to address the Court's ruling would be to establish a
numeric compliance standard for the time of peak dose, within the
period of geologic stability at Yucca Mountain, which NAS judged to be
``on the order of one million years.'' (NAS Report p. 2)
    In establishing our final standards, we have considered that the
level of uncertainty increases as the time period covered by DOE's
performance

assessment increases.\3\ Therefore, it is reasonable for us to consider
how the compliance standard itself might also need to change.
Specifically, we do not believe that extending the 10,000-year
individual-protection standard of 15 mrem/yr to apply for 1 million
years adequately accounts for the considerations outlined above or
represents a reasonable test of the disposal system (more extensive
discussion of uncertainty in performance assessments is in section
III.A.4 of this document, ``How Did We Consider Uncertainty and
Reasonable Expectation?''); see also 66 FR 32098. We turned back to the
international technical literature for advice regarding appropriate
points of comparison for doses projected over hundreds of thousands of
years. A number of sources suggested that natural sources of
radioactivity would provide an appropriate benchmark for such
comparisons. In exploring this approach further, we found that the
variation in background radiation across the United States covered a
wide range (from roughly 100 mrem/yr to 1 rem/yr), primarily because of
local variation in radon exposures. We chose for our proposal a level
of 350 mrem/yr, which is close to a widely-cited estimate of 300 mrem/
yr for the national average background radiation exposure (NAS Report
Table 2-1), but specifically represented the difference between
estimated background levels in Amargosa Valley and the State of
Colorado. This level was proposed for both the individual-protection
and human-intrusion standards as offering both a reasonable level of
protection and a sound basis for regulatory decision-making when
exposures are projected to occur hundreds of thousands of years into
the future. Selecting such a level would also provide an indication
that exposures incurred by the RMEI in the far future from the
combination of natural background radiation and releases from the Yucca
Mountain disposal system would not exceed exposures incurred by
residents of other parts of the country today from natural sources
alone. Today's final rule adopts a more stringent standard that is not
derived from an analysis of background radiation, as explained in
sections III.A.1 (``What is the Peak Dose Standard Between 10,000 and 1
Million Years After Disposal?'') and III.A.5 (``How Did We Consider
Background Radiation in Developing The Peak Dose Standard?'') of this
document.
---------------------------------------------------------------------------

    \3\ ``We recognize that there are significant uncertainties in
the calculations and that these uncertainties increase as the time
at which peak risk occurs increases.'' (NAS Report p. 56)
---------------------------------------------------------------------------

    Uncertainty in long-term projections also influenced our proposal.
Given the probabilistic nature of performance assessments, it is
possible that some combinations of parameter values will result in very
high doses, even if such combinations have an extremely low probability
of occurring. Although there may be only a few results that are very
high, extreme results have the potential to exert a strong influence on
the arithmetic mean, which could make the mean less representative of
all performance projections. This possibility may be increased by the
introduction of additional, and possible excessive, conservatisms as a
way to account for uncertainties. We expressed a preference for a
statistical measure that would not be strongly affected by either very
high- or low-end estimates, believing it appropriate to focus on the
``central tendency'' of the distribution, where the bulk of the results
might be expected to be found. We proposed the median of the
distribution as being most representative of central tendency. Because
it is always located at the point where half the distribution is higher
and half lower, the median depends only on the relative nature of the
distribution, rather than the absolute calculated values. Given our
concerns about specifying a peak dose compliance value against which
performance would be judged for a period up to 1 million years, we
believed the median might also provide a reasonable test of long-term
performance. Today's final rule departs from the proposal by adopting
the arithmetic mean as the statistical measure of compliance to be
applied at all times, as explained in section III.A.9 of this document
(``How Will NRC Judge Compliance?'').
    Our consideration of FEPs also was affected to some extent by
uncertainty, as well as by conclusions of the NAS committee. In our
proposal, the overall probability threshold for inclusion of FEPs
remained the same as in the 2001 rule, which we believe provides a very
inclusive initial screen that captures both major and minor factors
potentially affecting performance. Uncertainty plays a role in the
sense that very gradual or infrequent processes and events may begin to
influence performance only at times in the hundreds of thousands of
years, when the overall uncertainty of assessments is increasing. The
additional uncertainty introduced by these slow-acting FEPs led us to
propose the exclusion of FEPs if they were not significant to the
assessments in the initial 10,000 years. We believed this would still
provide for robust assessments that would address the factors of most
importance over the entire 1 million-year period. We did consider in
our proposal whether significant FEPs might not be captured using this
approach. In evaluating whether excluded FEPs might become more
probable or more significant after 10,000 years, and therefore should
not be eliminated, we identified general corrosion as a FEP that is
certain to occur and represents a significant failure mechanism at
longer times, even though it is less significant in the initial 10,000
years.
    We also consulted the NAS Report for advice on handling long-term
FEPs. NAS identified three ``modifiers'' that it believed could
reasonably be included in assessments: seismic events, igneous events,
and climate change. (NAS Report p. 91) We developed provisions
addressing these FEPs that incorporated the views expressed by the NAS.
For seismic and igneous events, we proposed that DOE focus its
attention on events causing direct damage to the engineered barriers.
We took this approach because failure of the engineered barrier system,
particularly the waste packages, is the predominant factor in
determining the timing and magnitude of the peak dose, and is the
overriding uncertainty in assessing performance of the disposal system.
To address climate change, we required DOE to focus on the effects of
increased water flow through the repository, which is the climatic
effect with the most influence on release and transport of
radionuclides. We determined that such a focus would provide the basis
for a reasonable test of the disposal system, and that climate change
beyond 10,000 years could be represented by constant conditions
reflecting precipitation levels that differ from current conditions,
which eliminates unresolvable speculation regarding the timing,
magnitude, and duration of climatic cycles over this time frame. We
also directed that NRC establish the exact nature of future climate
characteristics to be used in performance assessments. NRC subsequently
issued a proposal to specify a range of values for deep percolation
into the repository, which DOE would use as another parameter in its
probabilistic performance assessments. (70 FR 53313, September 8, 2005)
    Finally, we proposed to update the factors used to calculate dose
for the storage, individual-protection, and human-intrusion standards.
Our generic standards in 40 CFR part 191, and by inference our Yucca
Mountain standards in 2001, specified the factors associated with ICRP
Publications 26

and 30 (Docket Nos. EPA-HQ-OAR-2005-0083-0425 and 0428, respectively).
Since we issued 40 CFR part 191, ICRP has modified the models and
associated organ-weighting factors to more accurately calculate dose.
See ICRP Publications 60 and 72 (Docket Nos. EPA-HQ-OAR-2005-0083-0421
and 0427, respectively). We used this newer method in 1999 to develop
our Federal Guidance Report 13, ``Cancer Risk Coefficients from
Exposure to Radionuclides'' (Docket No. EPA-HQ-OAR-2005-0083-0072).
Where possible, we believe it is appropriate to adopt the latest
scientific methods.\4\
---------------------------------------------------------------------------

    \4\ ICRP published its most recent recommendations in
Publication 103, issued in 2007 (Docket No. EPA-HQ-OAR-2005-0083-
0423). EPA has not determined the impact of these recommendations on
its current dose and risk estimates, but may decide to adopt them in
the future. Today's final rule will incorporate the ICRP 60
recommendations as consistent with EPA's current federal guidance;
however, we have provided some flexibility for use of newer
dosimetry in the future if deemed appropriate by NRC.
---------------------------------------------------------------------------

C. In Making Our Final Decisions, How Did We Incorporate Public
Comments on the Proposed Rule?

    Section 801(a)(1) of the EnPA requires us to set public health and
safety radiation protection standards for Yucca Mountain by rulemaking.
Pursuant to Section 4 of the Administrative Procedure Act (APA),
regulatory agencies engaging in informal rulemaking must provide notice
of a proposed rulemaking, an opportunity for the public to comment on
the proposed rule, and a general statement of the basis and purpose of
the final rule.\5\ The notice of proposed rulemaking required by the
APA must ``disclose in detail the thinking that has animated the form
of the proposed rule and the data upon which the rule is based.''
(Portland Cement Association v. Ruckelshaus, 486 F. 2d 375, 392-94 (DC
Cir. 1973)) The public thus is enabled to participate in the process by
making informed comments on the proposal. This provides us with the
benefit of ``an exchange of views, information, and criticism between
interested persons and the agency.'' (Id.)
---------------------------------------------------------------------------

    \5\ 5 U.S.C. 553.
---------------------------------------------------------------------------

    There are two primary mechanisms by which we explain the issues
raised in public comments and our reactions to them. First, we discuss
broad or major comments in the succeeding sections of this preamble.
Second, we are publishing a document, accompanying today's action,
entitled ``Response to Comments'' (Docket No. EPA-HQ-OAR-2005-0083-
0431). The Response to Comments document provides more detailed
responses to issues addressed in the preamble. It also addresses all
other significant comments on the proposal. We gave all the comments we
received, whether written or oral, consideration in developing the
final rule.

D. What Public Comments Did We Receive?

    The public comment period ended November 21, 2005. We received more
than 300 individual submittals, although any particular submittal could
contain many specific comments. We also received many more submissions
as part of mass comment efforts, in which organizations encourage
commenters to use prepared texts or comment on specific aspects of the
proposal. All, or representative, comments are available electronically
through the Federal Document Management System (FDMS), available at
http://www.regulations.gov. See the ``General Information'' section of
this document for instructions on how to access the electronic docket.
Some submittals may be duplicated in FDMS, as a commenter may have used
several methods to ensure the comments were received, such as fax, e-
mail, U.S. mail, or directly through FDMS.
    A significant number of comments addressed the proposed peak dose
standard of 350 mrem/yr, which would apply between 10,000 and 1 million
years. Most commenters opposed our proposal, arguing that it is much
higher than any previous standard, is not protective, is not equitable
to future generations, and is based on inappropriate use of background
radiation data. Many commenters also took issue with our proposal to
use the median of the distribution of results as the statistical
measure between 10,000 and 1 million years, viewing this measure as
inconsistent with NAS recommendations to use the mean. Commenters also
viewed the median as too ``lax'' and likely to discount scenarios that
would result in high exposures. We also received comment on our
proposal concerning the assessment of FEPs beyond 10,000 years, with
some comments expressing the opinion that we had inappropriately
constrained the analyses, leaving out potentially significant FEPs.
Some commenters disagreed with our general premise that uncertainty
increases with assessment time and further disagreed that we should
take uncertainties into account when considering standards applicable
to the far future. These specific comments, and our responses to them,
will be discussed in more detail in section III of this document and in
the Response to Comments document associated with this action (Docket
No. EPA-HQ-OAR-2005-0083-0431).
    Some commenters also questioned our conclusion that extending the
compliance period is the appropriate way to respond to the Court
ruling. These commenters point out that the Court's opinion could be
interpreted to permit us to justify the approach taken in our 2001
standards. They cite statements by the Court such as ``[i]t would have
been one thing had EPA taken the Academy's recommendations into account
and then tailored a standard that accommodated the agency's policy
concerns'' and ``[h]ad EPA begun with the Academy's recommendation to
base the compliance period on peak dosage and then made adjustments to
accommodate policy considerations not considered by NAS, this might be
a very different case'' (NEI, 373 F.3d at 1270 and 1273, respectively)
to support the thesis that the Court's judgment was based primarily on
the presentation of our case, rather than the substance. In the
commenters' view, the Court would have been receptive to our arguments
had they been presented differently, and the Court provided a clear
``road map'' to justify keeping our original standards in place. In
addition, these and other commenters viewed extending the compliance
period to 1 million years as not justifiable either scientifically or
as a matter of public policy. We believe that the approach we are
taking is the most appropriate way to address the concerns raised by
the Court's decision, particularly given the weight accorded by the
Court to the NAS technical recommendations concerning the period of
geologic stability. As we stated in our proposal, ``it is not clear how
EPA's earlier explanation of its policy concerns might be reconciled
with NAS's technical recommendation.'' (70 FR 49032) Accordingly,
today's final rule implements the NAS technical recommendation with
regard to the length of time for the compliance period while still
accommodating our policy concerns in the provisions related to the peak
dose standard, and FEPs.
    We received some comments that suggested we should have provided
more or better opportunities for public participation in our decision
making process. For example, comments suggested that we should have
rescheduled public hearings, extended the public comment period, and
provided alternatives to the public hearing process. We provided
numerous opportunities and avenues for public participation in the
development of these standards. For example, we held public hearings in
Washington, DC; Las

Vegas, NV; and Amargosa Valley, NV. We also opened a 60-day public
comment period and met with key stakeholders before and during that
time. In response to requests from stakeholders, we extended the public
comment period by 30 days and held an additional public hearing in Las
Vegas. We conducted targeted outreach to Native American tribal groups
and have fully considered all comments received through December 31,
2005, after the end of the extended public comment period. These
measures are in full compliance with the public participation
requirements of the Administrative Procedure Act.
    Several commenters supported our role in setting standards for
Yucca Mountain. Other commenters thought that aspects of our standards
duplicate NRC's implementation role. We believe the provisions of this
rule clearly are within our authority and they are central to the
concept of a public health protection standard. We also believe our
standards leave NRC the necessary flexibility to adapt to changing
conditions at Yucca Mountain or to impose additional requirements in
its implementation efforts, if NRC deems them to be necessary.
    We also received many general comments, and others addressing
topics that are outside the scope of our authority under the EnPA. For
example, several commenters simply expressed their support for, or
opposition to, the Yucca Mountain repository. Other comments suggested
our standards should explicitly consider radiation exposures from all
sources because of the site's proximity to the Nevada Test Site (NTS)
and other sources of potential contamination. Also, a number of
commenters suggested that we should explore alternative methods of
waste disposal, such as neutralizing radionuclides. Comments also
expressed concern regarding risks of transporting radioactive materials
to Yucca Mountain. These comments all raise considerations that are
outside the scope of our authority and this rulemaking.
    Many comments touched on issues related to our authority and
standards, but outside the limited scope of this rulemaking. In
particular, many comments urged us to extend the ground-water
protection limits to the time of peak dose within the 1 million-year
compliance period. Many of these commenters disagreed with our position
that the ground-water standards were not the subject of the Court's
ruling, and that in fact the Court left us with discretion regarding
the content and application of those standards. Others believed that we
are obligated to accept comments on this topic, since we were proposing
not to change the standards. We stated clearly in our proposal that we
were not soliciting, and would not consider, comments on this issue.

III. What Final Amendments Are We Issuing With This Action?

    This section describes the provisions of our final rule, our
rationale, and our response to public comments on various aspects of
our proposal. Today's final rule establishes the dose standards
applicable for a period up to 1 million years after disposal, the
statistical measures used to determine compliance with those standards,
the methods to be used to calculate the dose, and the requirements for
including features, events, and processes (FEPs) in the performance
assessments.

A. What Dose Standards Will Apply?

    Today's final rule includes an individual-protection standard
consisting of two parts, which will apply over different time frames.
The post-10,000-year public health protection standard limits the long-
term peak dose to the RMEI from the Yucca Mountain disposal system to 1
mSv/yr (100 mrem/yr) committed effective dose equivalent (CEDE). This
post-10,000-year (also referred to as the ``peak dose'') standard
addresses and responds to the DC Circuit ruling that our 2001
standards, with the compliance period limited to 10,000 years, were
inconsistent with the recommendations of the NAS. The post-10,000-year
standard was the focus of our proposal and will apply after 10,000
years through the period of geologic stability, up to 1 million years
after disposal. The other part of the individual-protection standard,
which will apply over the initial 10,000 years after disposal, consists
of the 150 [mu]Sv/yr (15 mrem/yr) CEDE individual-protection standard
promulgated in 2001 as 40 CFR 197.20. We believe this approach
maintains an appropriate emphasis on the initial condition of the
repository and its critical early evolution, including the period when
thermal stresses will be most significant.\6\ As the disposal system
evolves, today's final rule establishes a peak dose standard for the
period up to 1 million years that is responsive to the Court's ruling,
consistent with the NAS recommendation to establish a compliance
standard for the time of peak risk, and satisfies our statutory mandate
to protect public health and safety. The final rule also provides a
reasonable test of disposal system performance by appropriately
recognizing the relatively more difficult challenge in treating the
uncertainties associated with projecting performance to such distant
times, and the resulting lessened level of confidence that can be
derived from such performance projections.
---------------------------------------------------------------------------

    \6\ We noted in our 2001 rule: ``Focusing upon a 10,000-year
compliance period forces more emphasis upon those features over
which humans can exert some control, such as repository design and
engineered barriers. Those features, the geologic barriers, and
their interactions define the waste isolation capability of the
disposal system. By focusing upon an analysis of the features that
humans can influence or dictate at the site, it may be possible to
influence the timing and magnitude of the peak dose, even over times
longer than 10,000 years.'' (66 FR 32099)
---------------------------------------------------------------------------

    As we noted in our proposal, there was no legal challenge to, and
the Court made no ruling on, the protectiveness of our standards up to
10,000 years. Further, the Court ruled that we must address peak dose,
but did not state, and we do not believe intended, that we could not
have additional measures to bolster the overall protectiveness of the
standard. We believe that promulgating the post-10,000-year peak dose
standard to protect public health and safety while retaining a separate
individual-protection standard that focuses attention on the early
evolution of the repository in the pre-10,000-year period enhances the
overall protectiveness of our rule and is consistent with the findings
and recommendations of the NAS committee. As the Court noted, the EnPA
requires that EPA ``establish a set of health and safety standards, at
least one of which must include an EDE-based, individual protection
standard'' (NEI, 373 F.3d at 1281), but does not restrict us from
issuing additional standards. Thus, as long as we address the NAS
recommendation regarding peak dose, as we are doing today by issuing
the post-10,000-year standard, we are not precluded from issuing other,
complementary, standards to apply for a different compliance period.
The Court's concern was whether we had been inconsistent with the NAS
recommendation by not extending the period of compliance to capture the
peak dose ``within the limits imposed by the long-term stability of the
geologic environment.'' (NAS Report p. 2) Today's final rule defines
the period of geologic stability for purposes of compliance as ending
at 1 million years after disposal. We believe our decision to retain a
separate standard applicable for the first 10,000 years after disposal
during this period, along with ``at least one * * * EDE-based,
individual protection standard'' applying to the peak dose during the
period of geologic

stability between 10,000 years and 1 million years, protects public
health and safety pursuant to the EnPA, complies with the Court's
decision, falls well within our policy discretion and is supported by
scientific considerations concerning the impact of uncertainties in
projecting doses over extremely long time frames, as discussed in
Section III.A.4 of this document (``How Did We Consider Uncertainty and
Reasonable Expectation?'').
    The NAS Report recognized the possible outcome of a rulemaking
establishing separate standards that apply over different time periods.
As discussed in more detail in Section III.A.6 (``How Does Our Rule
Protect Future Generations?''), the committee contrasted an approach in
which ``a health-based risk standard could be specified to apply
uniformly across time and generations'' with ``some other expression of
the principle of intergenerational equity'' to be determined by
``social judgment.'' (NAS Report pp. 56-57) The committee also
recognized, as we have just explained, that ``the scientific basis for
analysis changes with time'' in potentially significant ways as the
time to peak dose increases. (NAS Report pp. 30-31) We also find it
useful to consider the testimony of Mr. Robert Fri, chair of the NAS
committee, before the Senate Environment and Public Works Committee on
March 1, 2006, in his personal capacity, wherein he pointed out that
``the specification of the time horizon and the selection of the person
to be protected are intimately connected.'' As a result, he explained
that retaining the RMEI as the receptor (which the NAS committee
recognized as more conservative than, but ``broadly consistent'' with,
its preferred probabilistic critical group \7\) while at the same time
extending the compliance period ``runs the risk of excessive
conservatism,'' potentially putting the rule where the ``committee
specifically did not want to be.'' He noted that the committee had
considered and rejected such an approach. (See NAS Report pp. 100-103)
Mr. Fri viewed our proposal of a higher dose limit between 10,000 and 1
million years as a way ``to avoid becoming overly conservative.''
Therefore, while he (like the NAS committee itself) offered no opinion
on the level of the proposed post-10,000-year standard, he indicated
that, in his opinion, our approach was not in conflict with the
committee's intention, and would be closer to the committee's overall
goal than would applying the 15 mrem/yr standard to the 1 million-year
compliance period. He concluded by stating ``the committee recognized
that EPA properly had considerable discretion in applying policy
considerations outside the scope of our study to the development of the
health standard for Yucca Mountain.'' (See generally NAS Report p. 3)
See the hearing transcript at Docket No. EPA-HQ-OAR-2005-0083-0380 and
Mr. Fri's prepared testimony at Docket No. EPA-HQ-OAR-2005-0083-0402.
We believe the decision to establish two compliance standards falls
well within our policy discretion and in that context the 10,000-year
individual-protection standard is analogous to our ground-water
protection standards, which were also not addressed by NAS
recommendations.
---------------------------------------------------------------------------

    \7\ In discussing an alternative subsistence-farmer receptor,
the committee noted that ``it makes the most conservative assumption
that wherever and whenever the maximum concentration of
radionuclides occurs in a ground water plume accessible from the
surface, a farmer will be there to access it.'' (NAS Report p. 102)
We have defined the RMEI to incorporate this same assumption.
---------------------------------------------------------------------------

1. What Is the Peak Dose Standard Between 10,000 and 1 Million Years
After Disposal?
    In establishing a public health and safety standard applicable at
the time of peak dose, as required by the EnPA and recommended by the
NAS, and after considering public comments on the issue, today's final
rule adopts a more stringent standard than the proposed 3.5 mSv/yr (350
mrem/yr) standard. Specifically, we are today establishing an
individual-protection standard of 1 mSv/yr (100 mrem/yr) to apply
beyond 10,000 years and up to 1 million years after disposal.
    As discussed in more detail later in this section, NAS expressly
refrained from recommending any specific dose or risk limit for the
compliance standard, but instead described ``the spectrum of
regulations already promulgated that imply a level of risk, all of
which are consistent with recommendations from authoritative radiation
protection bodies'' for EPA's consideration. (NAS Report p. 49)
Further, while NAS stated that a single standard ``could be specified
to apply uniformly over time and generations,'' it also recognized that
other approaches are possible as ``a matter for social judgment.'' (NAS
Report pp. 56-57) NAS also recognized that the level of protection was
a matter best left to EPA to establish through rulemaking: ``We do not
directly recommend a level of acceptable risk.'' (NAS Report p. 49) NAS
further noted that, while ``there is a considerable body of analysis
and informed judgment from which to draw in formulating a standard for
the proposed Yucca Mountain repository,'' ``EPA's process for setting
the Yucca Mountain standard is presumably not bound by this
experience.'' (NAS Report p. 39) Thus, the NAS Report contains no
finding or recommendation as to the dose limit at the time of peak dose
in our Yucca Mountain standards.
    In selecting this final standard, we started with a range of annual
fatal cancer risk (10-5 to 10-6) that encompassed
the 15 mrem/yr standard established in 2001 for the initial 10,000
years after disposal. We also considered the ``starting range''
identified by NAS in determining the appropriate level for the
individual-protection standard to apply in the time period beyond
10,000 years. (NAS Report p. 49 and Tables 2-3 and 2-4) For the reasons
discussed below, we determined that it would not be reasonable to apply
a standard within that starting range for the entire million-year
compliance period. Rather, we identified dose levels that are
protective of public health and safety and that reasonably accommodate
our policy concerns regarding the implementation of a compliance
standard for 1 million years. For the same reasons, the Agency has
determined that it is not reasonable to apply its traditional risk-
management policies when establishing a compliance standard applicable
for periods beyond 10,000 years and up to 1 million years (see section
III.A.3, ``How Do Our Standards Protect Public Health and Safety?'').
EPA does not believe it is realistic to demand that projections for
such complex systems over this far future time frame be readily
distinguishable at the level of incremental risk customarily addressed
by the Agency in situations where results can be confirmed, modeling is
utilized on a more limited scale, or institutional controls are more
applicable.
    In selecting 100 mrem/yr as the peak dose standard for the period
beyond 10,000 years, we took particular note of the NAS's discussion of
that dose level: ``Consistent with the current understanding of the
related consequences, ICRP, NCRP, IAEA, UNSCEAR, and others have
recommended that radiation doses above background levels to members of
the public not exceed 1 mSv/yr (100 mrem/yr) effective dose for
continuous or frequent exposure from radiation sources other than
medical exposures. Countries that have considered national radiation
protection standards in this area have endorsed the ICRP recommendation
of 1 mSv per year radiation dose limit above natural background
radiation for members of

the public.'' (NAS Report pp. 40-41) We also note that the 100 mrem/yr
level is included in the range of regulations offered by NAS for EPA's
consideration. (NAS Report Table 2-3)
    Therefore, as we discussed in our proposal, a dose level of 100
mrem/yr level is well-established as protective of public health under
current dose limits, and, as such, represents a robust public health
protection standard in the extreme far future. (70 FR 49040) As noted
by NAS, international organizations such as ICRP, IAEA, and NEA
recommend its use as an overall public dose limit in planning for
situations where exposures may be reasonably expected to occur.
Although it had used the concept of public dose limits previously, ICRP
first described its recommendations for a comprehensive system of
radiation protection in Publication 60 (``1990 Recommendations of the
ICRP'') (Docket No. EPA-HQ-OAR-2005-0083-0421). ICRP considered two
referents in recommending a public dose limit: health detriment and
``variation in the existing level of dose from natural sources.'' ICRP
concluded that estimates of health detriment ``suggest a value of the
annual dose limit not much above 1 mSv.'' Similarly, ``[e]xcluding the
very variable exposures to radon, the annual effective dose from
natural sources is about 1 mSv, with values at high altitudes above sea
level and in some geological areas of at least twice this. On the basis
of all these considerations, the Commission recommends an annual limit
on effective dose of 1 mSv.'' (Paragraphs 190-191) ICRP re-affirmed
this position in its most recent recommendations: ``For public exposure
in planned exposure situations, the Commission continues to recommend
that the limit should be expressed as an effective dose of 1 mSv in a
year.'' (Publication 103, Paragraph 245, Docket No. EPA-HQ-OAR-2005-
0083-0423)
    This recommendation as to a 100 mrem/yr public dose limit was
adopted in the 1996 ``International Basic Safety Standards for
Protection Against Ionizing Radiation and for the Safety of Radiation
Sources,'' which was jointly sponsored by IAEA, NEA, the Food and
Agriculture Organization of the United Nations, the International Labor
Organization, the Pan American Health Organization, and the World
Health Organization. (IAEA Safety Series 115, Schedule II, Docket No.
EPA-HQ-OAR-2005-0083-0409) It should also be noted that the European
Union requires its Member States to incorporate this 100 mrem/yr public
dose limit into national law or regulation (Council Directive 96/29/
EURATOM of 13 May 1996, Docket No. EPA-HQ-OAR-2005-0083-0410). Non-EU
countries such as Argentina, Australia, Canada, and Japan also
incorporate this public dose limit into their systems of regulation, as
shown by their national reports under the Joint Convention on the
Safety of Spent Fuel Management and on the Safety of Radioactive Waste
Management (see http://www-ns.iaea.org/conventions/waste-
jointconvention.htm). The United States is also a Contracting Party to
the Joint Convention (Docket No. EPA-HQ-OAR-2005-0083-0393).
    Domestically, both NRC and DOE incorporate the 100 mrem/yr level
into their systems of regulation (10 CFR 20.1301 and DOE Order 5400.5,
respectively), and NCRP also endorses the ICRP system of protection
(NCRP Report 116, ``Limitation of Exposure to Ionizing Radiation,''
Docket No. EPA-HQ-OAR-2005-0083-0407). In setting today's peak dose
standard, EPA acknowledges and concurs in the broad consensus in the
protectiveness of the 100 mrem/yr level and, furthermore, considers it
especially suitable for application to the extreme far future, when
planning for and projecting public exposures is much less certain.
    For all these reasons, we conclude that the 100 mrem/yr peak dose
standard we are establishing today for the period beyond 10,000 years
will protect public health and safety. By considering international
guidance and examples, we have derived a final peak dose limit that
balances the competing factors highlighted by NAS and acknowledged by
us as important: the dual objectives of promulgating a standard that is
protective of the health and interests of future generations, and also
effectively addressing the effects of uncertainty on compliance
assessment. Moreover, the 100 mrem/yr level is comparable to the
domestic and international standards NAS suggested that EPA consider.
(NAS Report p. 49 and Tables 2-3 and 2-4)
    Our selection of a 100 mrem/yr standard is therefore protective and
reasonable in that it effectively addresses the factors it is necessary
to consider when projecting exposures very far into the future. By
applying this standard over the entire period of geologic stability
beyond 10,000 years (up to 1 million years), our approach is consistent
with the NAS recommendation to have a standard with compliance measured
``at the time of peak risk, whenever it occurs, within the limits
imposed by the long-term stability of the geologic environment, which
is on the order of one million years.'' (NAS Report p. 2)
    Although we have not used specific estimates of background
radiation in determining our final peak dose standard, as we had
proposed, we note that the 100 mrem/yr level reasonably comports with
such an analysis as well. For example, it is comparable to outdoor
(unshielded) measurements of cosmic and terrestrial radiation in
Amargosa Valley. When shielding from buildings is considered and indoor
radon doses are estimated using a more conservative conversion factor
suggested by some commenters, 100 mrem/yr is at the low end of overall
background radiation estimates in Amargosa Valley and nationally.\8\
Within the State of Nevada, the difference in average estimates of
background radiation for counties is greater than 100 mrem/yr. (Docket
No. EPA-HQ-OAR-2005-0083-0387) This suggests that 100 mrem/yr can be
considered to be a level such that the total potential doses incurred
by the RMEI from the combination of background radiation and releases
from Yucca Mountain will remain below doses incurred by residents of
other parts of the country from natural sources alone. See Section
III.A.5 of this document for more discussion of background radiation
(``How Did We Consider Background Radiation in Developing the Peak Dose
Standard?'').
---------------------------------------------------------------------------

    \8\ NAS cited an estimate of 300 mrem/yr as the national average
for natural background radiation (cosmic, terrestrial, radon, and
radioactive isotopes internal to the human body). (NAS Report Table
2-1) This is the best-known estimate of average natural background
in the U.S., but does not use the more conservative radon dose
conversion factor provided by public comments.
---------------------------------------------------------------------------

    Our proposal discussed several factors that we considered to be
important in setting a dose standard for the time of peak dose within
the period of geologic stability. We emphasized the cumulative and
increasing uncertainty in projecting potential doses over great time
periods, and argued against viewing projected doses as predictions of
disposal system performance. This is consistent with the position taken
by the NAS committee: ``The results of compliance analysis should not,
however, be interpreted as accurate predictions of the expected
behavior of a geologic repository.'' (NAS Report p. 71)
    We also have considered how the role of quantitative projections in
making compliance decisions must change as the time covered by those
projections increases to the extreme far future. We noted that
emphasizing incremental dose increases when such increases may be
overwhelmed by fundamental uncertainties inappropriately takes
attention away from an evaluation of the

overall safety of the disposal system, which may rest equally on other
lines of evidence, such as confidence in the long-term stability of the
site or reference to natural analogues. In our view, in order to
provide a reasonable test of the disposal system, the role of the peak
dose standard in the overall decision of disposal system safety must be
consistent with the relative confidence that can be placed in
quantitative projections over extremely long times. We have recognized
the strong consensus in the international radioactive waste community
that dose projections extending many tens to hundreds of thousands of
years into the future can best be viewed as qualitative indicators of
disposal system performance, rather than as firm predictions that can
be compared against strict numerical compliance criteria. In fact,
international organizations have treated such numerical criteria in a
more flexible way and supported their application in conjunction with
other qualitative considerations in applying them to regulatory
determinations over very long time frames.\9\ Further, we agree that
confidence in the way the projections were performed, and the
consideration of supporting qualitative information, may be more
important to an overall judgment of safety at longer times.\10\
However, our task is to establish a numerical compliance limit, rather
than a qualitative standard or dose target. Therefore, we believe it is
appropriate in setting that limit to evaluate and apply the
considerations that have led the international radiation protection
community to view long-term projections in a more qualitative manner.
---------------------------------------------------------------------------

    \9\ The 2007 NEA document on ``Consideration of Timescales in
Post-Closure Safety of Geological Disposal of Radioactive Waste,''
which is based on surveys of NEA Member Countries, states
``Calculated values of dose and risk are therefore viewed in
regulations not as predictions but rather as indicators or measures
of protection that are used to test the capability of the system to
provide isolation of the waste and containment of radionuclides (the
`dose' that is being calculated is what radio-protectionists refer
to as `potential dose'). These indicators are to be evaluated on the
basis of models that include certain stylized assumptions, in
particular regarding the biosphere and human lifestyle or actions.''
(Docket No. EPA-HQ-OAR-2005-0083-0411, p. 38) NEA also notes:
``There is agreement that calculations of dose and risk in the
future are illustrations of possible system behaviour rather than
predictions of outcomes, and there is consensus that, in the long
term, numerical criteria for radioactive waste disposal should be
considered as references or indicators, addressing the ultimate
safety objectives, rather than as absolute limits in a legal
context.'' (``Regulating the Long-Term Safety of Geological
Disposal: Towards a Common Understanding of the Main Objectives and
Bases of Safety Criteria,'' NEA-6182, Docket No. EPA-HQ-OAR-2005-
0083-0408, p. 24) Similarly, ICRP Publication 81 contrasts the
approach of ``consideration of quantitative estimates of dose or
risk on the order of 1000 to 10,000 years'' with ``consideration of
quantitative calculations further into the future making increasing
use of stylized approaches and considering the time periods when
judging the calculated results. Qualitative arguments could provide
additional information to this judgmental process.'' (Docket No.
EPA-HQ-OAR-2005-0083-0417, Paragraph 71) The IAEA consensus document
for geologic disposal (``Safety Requirements for Geological Disposal
of Radioactive Waste,'' WS-R-4, 2006) states: ``It is recognized
that radiation doses to individuals in the future can only be
estimated and that the uncertainties associated with these estimates
will increase for times farther into the future. Care needs to be
exercised in using the criteria beyond the time when the
uncertainties become so large that the criteria may no longer serve
as a reasonable basis for decisionmaking.'' (Docket No. EPA-HQ-OAR-
2005-0083-0383, Paragraph 2.12)
    \10\ Such considerations are not unusual in other applications.
For example, in making plans based on weather forecasts, one can
expect the next-day forecast to be fairly accurate. However, one has
to recognize that the same degree of accuracy cannot be expected
from longer-range forecasts. In that case, one would want to have
confidence that the forecast is based upon the most current
scientific understanding of weather patterns.
---------------------------------------------------------------------------

    We conclude that a peak dose standard of 100 mrem/yr for the Yucca
Mountain disposal system for the period between 10,000 and 1 million
years protects public health and safety. Setting the standard as we
have is also consistent with the NAS committee's decision not to
recommend a level for the final peak standard and EPA's broad
discretion to establish standards that are protective while
accommodating technical and policy concerns inherent in projecting and
evaluating potential events hundreds of thousands of years into the
future. See section III.A.3 of this document for more discussion of the
protectiveness of our standards (``How Does Our Final Rule Protect
Public Health and Safety?'').
    The ICRP recommendation for a public dose limit of 100 mrem/yr
relates to the total exposure to members of the public from all manmade
sources (excluding occupational, accidental, and medical, which can be
significantly higher). A number of comments took issue with our
approach and suggestion that it might be reasonable to ``apportion''
the entire 100 mrem/yr to the Yucca Mountain disposal system because of
the lack of other potential sources in the region, and that this could
be considered consistent with the NAS recommendation to rely on current
conditions and present knowledge. The comments expressed the view that
such an approach would be entirely contrary to the NAS recommendation
to apply apportionment, as well as to the principle of apportionment
itself, which recognizes the potential for new or additional sources of
exposure to be developed.
    NAS made no recommendation or finding regarding apportionment. In
its discussion of apportionment, NAS noted that the concept had been
widely adopted (NAS Report pp. 40-41). NAS also noted that ``guidance
to date has been for expected exposures from routine practices. There
is little guidance on potential exposures in the far distant future.''
(NAS Report p. 41). NAS made no specific recommendation that EPA apply
the concept to Yucca Mountain, let alone how the concept should be
applied.
    Further, given our statutory obligation under the EnPA to establish
a site-specific standard, allocating 100 mrem/yr to a single source at
the time of peak dose is reasonable because other contributors
currently in the Yucca Mountain area are negligible by comparison
(FEIS, DOE/EIS-0250, section 8.3.2, Docket No. EPA-HQ-OAR-2005-0083-
0086). By relying on current conditions, as recommended by NAS, rather
than speculating on potential future sources of exposure to the local
population, it is reasonable for EPA to allocate the entire 100 mrem/yr
to the Yucca Mountain disposal system. By assuming that current
conditions will apply in the future, we are applying an approach
routinely applied internationally, as well as by EPA in its WIPP
compliance criteria (the ``future states'' assumption at 40 CFR
194.25).\11\
---------------------------------------------------------------------------

    \11\ For example, IAEA notes that in modeling over longer time
frames, ``The emphasis of assessment should therefore be changed so
that the calculations relating to the near-surface zone and human
activity are simplified by assuming present day communities under
present conditions.'' (TECDOC-767, Docket No. EPA-HQ-OAR-2005-0083-
0044, p. 19) The French Basic Safety Rule III.2.f specifies that
``The characteristics of man will be considered to be constant
(sensitivity to radiation, nature of food, contingency of life, and
general knowledge without assuming scientific progress, particularly
in the technical and medical fields).'' (Docket No. EPA-HQ-OAR-2005-
0083-0389, Section 3.2)
---------------------------------------------------------------------------

    EPA's application of the concept of apportionment is, moreover,
reasonable. We addressed the apportionment approach in conjunction with
our 10,000-year standard of 15 mrem/yr as consistent with EPA's overall
risk management approach and past actions. However, we do not agree
that it is either required or reasonable to follow the apportionment
approach over hundreds of thousands of years, when the level of
uncertainty in dose projections is significantly increased and the
ability to project the performance of engineered barriers and the
overall disposal system with a high degree of certainty decreases. This
position is consistent with general

international practice and guidance, in which regulatory judgments rely
less on compliance with quantitative standards and more on other
qualitative factors supporting the overall safety case. Thus, for
example, IAEA recognizes in the consensus document ``Safety
Requirements for Geological Disposal of Radioactive Waste'' (WS-R-4,
Docket No. EPA-HQ-OAR-2005-0083-0383) the general agreement of the
geologic disposal community that, while apportionment is pertinent to
geologic disposal, it cannot be assumed to apply indefinitely.\12\
Moreover, IAEA reaches this conclusion on the basis of uncertainty in
projecting exposure from a specific long-term source, without regard to
the presumed knowledge, or lack thereof, of other potential sources of
exposure. We believe our approach is consistent with the long-held
international view of 10,000 years generally as a demarcation point
prior to which quantitative dose projections can be reasonably well-
managed, but beyond which those projections become progressively more
uncertain and less valuable.\13\ In our view, it is preferable to
follow this well-established precedent rather than to attempt to define
a different transition point based on the level and timing of
uncertainty in dose projections. As discussed in more detail later in
this section, countries that have established dose or risk standards
for geologic disposal have typically applied them for 10,000 years or
less, suggesting that this is a period of time within which standards
comparable to those applied to current practices can ``serve as a
reasonable basis for decision making.'' Beyond that time, the initial
``criteria,'' or dose standards, are viewed more qualitatively or
entirely different criteria that are not expressed in terms of risk or
dose are applied.\14\
---------------------------------------------------------------------------

    \12\ In describing criteria relevant to apportionment, IAEA
states: ``It is recognized that radiation doses to individuals in
the future can only be estimated and that the uncertainties
associated with these estimates will increase for times farther into
the future. Care needs to be exercised in using the criteria beyond
the time when the uncertainties become so large that the criteria
may no longer serve as a reasonable basis for decision making.''
(Paragraph 2.12, emphasis added) Similarly, NEA cites IAEA and ICRP
in noting that ``Generally speaking, these documents recommend that
the same criteria should be used as are applied for radiation
protection from current practices. These documents also recognise,
however, that such criteria cannot be applied in the same way for
the distant future as they are for current practices.'' (NEA-6182,
Docket No. EPA-HQ-OAR-2005-w0083-0408, p. 19, emphasis added)
    \13\ ICRP clearly expresses this view in Publication 81: ``To
evaluate the performance of waste disposal systems over long time
scales, one approach is the consideration of quantitative estimates
of dose or risk on the order of 1000 to 10,000 years. This approach
focuses on that period when the calculation of doses most directly
relates to health detriment and also recognises the possibility that
over longer time frames the risks associated with cataclysmic
geologic changes such as glaciation and tectonic movements may
obscure risks associated with the disposal system. Another approach
is the consideration of quantitative calculations further into the
future making increased use of stylised approaches and considering
the time periods when judging the calculated results. Qualitative
arguments could provide additional information to this judgmental
process.'' (Docket No. EPA-HQ-OAR-2005-0083-0417, Paragraph 71)
Similarly, IAEA suggests that within 10,000 years, ``While it is
recognized that considerable uncertainty can exist during this time
period, it is still reasonable to attempt to make quantitative
estimates of the indicators to be used.'' However, beyond that time,
``While it may be possible to make general predictions about
geological conditions, the range of possible biospheric conditions
and human behaviour is too wide to allow reliable modeling * * *
Such calculations can therefore only be viewed as illustrative and
the `doses' as indicative.'' (``Safety Indicators in Different Time
Frames for the Safety Assessment of Underground Radioactive Waste
Repositories,'' TECDOC-767, Docket No. EPA-HQ-OAR-2005-0083-0044,
pp. 18-19)
    \14\ France applies a dose standard for the first 10,000 years
that ``will be applied for determining the acceptability of the
radiological consequences.'' However, at later times, ``the same [25
mrem/yr] limit shall be used as a reference value.'' (Basic Safety
Rule III.2.f, Section 3.2.1, Docket No. EPA-HQ-OAR-2005-0083-0389,
emphasis added) Sweden specifies quantitative analyses to be judged
against a numerical standard for the first 1,000 years, but requires
examination of ``various possible sequences for the development of
the repository's properties, its environment and the biosphere''
after that time. (SSI FS 1998:1, Docket EPA-HQ-OAR-2005-0083-0047)
Similarly, Finland applies a dose standard for ``at least several
thousands of years,'' but when ``human exposure'' is no longer
``adequately predictable,'' an activity release standard is in
place. (YVL 8.4, Docket EPA-HQ-OAR-2005-0083-0392)
---------------------------------------------------------------------------

    Moreover, we note that under 10 CFR 20.1301, NRC requires that
licensees conduct operations so that the total effective dose
equivalent to individual members of the public from ``the licensed
operation'' does not exceed 100 mrem/yr. Thus, this regulatory limit
applies to individual licensees operating today, without reference to
other potential sources of exposure to the public. Of course, some
types of NRC licensees, such as fuel cycle facilities subject to our
standards in 40 CFR part 190, must meet dose constraints lower than the
100 mrem/yr limit. Nonetheless, 100 mrem/yr is the public dose limit
from licensed operations imposed in NRC regulations.
    We disagree with those comments generally questioning both the
legality and the protectiveness of our proposal to establish a long-
term standard higher than 15 mrem/yr. As described previously in
section III.A (``What Dose Standards Will Apply?''), commenters stated
that the NAS Report and Court decision required us to retain a single
dose standard (i.e., 15 mrem/yr) for the entire 1 million-year
compliance period, equivalent to the period of geologic stability
defined in our rule. Commenters pointed out that the proposed level was
well above the range identified by NAS as a starting point for our
rulemaking, and therefore stated that only the 15 mrem/yr level could
be considered consistent with the committee's recommendation.
Similarly, some commenters interpreted the Court ruling to require us
to adjust the time period covered by the existing 15 mrem/yr standard,
which was not challenged. We do not believe this interpretation to be
correct. It should be emphasized that NAS identified a range of risks
represented by current national and international standards, ``all of
which are consistent with recommendations from authoritative radiation
protection bodies,'' suggested only a ``reasonable starting point'' for
our rulemaking, and that none of the regulatory precedents considered
by NAS applied for periods approaching 1 million years. (NAS Report pp.
5 and 49, respectively) In fact, NAS explicitly declined to recommend a
level of protection, recognizing that this was a matter best left to
EPA to establish through rulemaking: ``We have not recommended what
levels of risk are acceptable * * * The specific level of acceptable
risk cannot be identified by scientific analysis, but must rather be
the result of a societal decision-making process. Because we have no
particular authority or expertise for judging the outcome of a properly
constructed social decision-making process on acceptable risk, we have
not attempted to make recommendations on this important question.''
(NAS Report p. 20) Indeed, NAS explicitly acknowledged ``that
determining what risk level is acceptable is not ultimately a question
of science but of public policy.'' (NAS Report p. 5) Further, NAS noted
that the final outcome of the rulemaking might diverge substantially
from the starting point suggested by NAS: ``Finally we have identified
several instances where science cannot provide all of the guidance
necessary to resolve an issue * * * In these cases, we have tried to
suggest positions that could be used by the responsible agency in
formulating a proposed rule. Other starting positions are possible, and
of course the final rule could differ markedly from any of them.'' (NAS
Report p. 3, emphasis added) Thus, we agree with NAS that the selection
of a level for the peak dose standard is one of the regulatory policy
issues left to EPA's discretion by the EnPA. As stated earlier, we find
that the annual risk associated with the final peak dose standard of
100 mrem/yr is

protective of public health and comparable to the domestic and
international standards NAS suggested that EPA consider, particularly
when considering the extended time frames under consideration for this
rulemaking. (NAS Report p. 49 and Tables 2-3 and 2-4)
    We also find it instructive to consider again the personal Senate
testimony of NAS committee chair Robert Fri, as described in Section
III.A (``What Dose Limits Will Apply?'') (Docket Nos. EPA-HQ-OAR-2005-
0083-0380 and 0402). Mr. Fri noted that simply extending the compliance
period in our 2001 rule to 1 million years ``runs the risk of excessive
conservatism'' and could place our standard where the ``committee
specifically did not want to be.'' He recognized that a higher standard
at the time of peak dose would be one way to reduce that conservatism.
Mr. Fri did not address the consistency of our proposed dose level with
the NAS findings and recommendations; however, he indicated that, in
his view, retaining the 15 mrem/yr standard at the time of peak dose
would not be consistent with those findings and recommendations if
other aspects of our rule remained unchanged (specifically, the choice
of receptor). We find this perspective noteworthy, in that it suggests
that there are circumstances in which applying 15 mrem/yr throughout
the 1 million-year compliance period could result in a standard
contrary to the committee's overall goals, which emphasized the use of
``cautious, but reasonable'' assumptions and care in the use of
``pessimistic scenarios and parameter values.'' (NAS Report pp. 100 and
79, respectively)
    Further, we do not believe the Court's decision provides direction
independent of the NAS Report; rather, the decision requires only that
we ensure that our standards are consistent with the NAS committee's
findings and recommendations, as required by the EnPA.
    In considering appropriate dose standards for periods approaching 1
million years, we also considered the development of our generic
standards in 40 CFR part 191. In both our 1985 and 1993 rulemakings
establishing those generic standards, we emphasized that the 10,000-
year compliance period for both the containment requirements and
individual-protection limit would lead to a combination of site
characteristics and engineered barriers that would be capable of
providing containment and isolation of the waste for these long periods
of time. We did not, however, anticipate that such performance could be
maintained indefinitely. Our generic technical analyses, in fact,
suggested that significant releases and doses to individuals could
result at later times, depending on the characteristics of the site in
question and the presumed location of the receptor. (See 58 FR 66401,
December 20, 1993)
    We note that sites whose natural features alone did not provide
total containment were not necessarily considered unsuitable, but we
recognized that in those instances, the focus would have to be on ``the
design of more robust engineered barrier systems capable of
significantly impeding radionuclide releases.'' We believe that it is
unrealistic to assume that these sites would then exhibit better
performance after the failure of those barriers than they would in the
initial 10,000-year period. Consequently, we believe that the potential
for doses higher than 15 mrem/yr to individuals in the far future has
always been implicit in the concept of geologic disposal. Over time,
the initial static system consisting of intact waste packages and other
engineered barriers in the natural geologic setting gives way to a more
dynamic system in which episodic and gradual processes combine to
transport radionuclides to the accessible environment. The sequence and
timing of barrier failures strongly influence, and introduce
considerable uncertainty into, the timing and magnitude of projected
doses over the 1 million-year period. The range of projected doses
widens considerably as the containment capability of the engineered
barriers diminishes. Interpreting the safety of the disposal system for
regulatory purposes, in our judgment, involves more than comparison of
projected doses to a regulatory standard, and a single standard
applicable to the initial static system would not adequately capture
the essential nature of a system that will evolve over 1 million years.
    In developing our final standards, we have given much attention to
guidance from international organizations and examples from specific
national programs. In general, we find few similarities in the details
of the international approaches that are directly applicable, and no
clear basis for comparing the different approaches. At the same time,
we did find broad points of similarity in the overall approach to long-
term projections, and referred in our proposal to organizations such as
IAEA and NEA, as well as specific countries, such as Sweden. The more
typical approach internationally is to require compliance with
quantitative performance assessment for only a limited period of time
(in some cases, less than 10,000 years). Longer-term dose projections
may be compared to dose or risk targets or reference levels, but are
viewed more as qualitative indicators of performance than as ``accurate
predictions of the expected behavior of a geologic repository'' (NAS
Report p. 71), to be weighed in conjunction with other qualitative
arguments for confidence in the overall safety of the facility. At
longer times, the weight given to quantitative projections typically
decreases.\15\ More detailed discussion of specific international
approaches may be found in Section 4 of the Response to Comments
document for this final rule (Docket No. EPA-HQ-OAR-2005-0083-0431).
---------------------------------------------------------------------------

    \15\ The standard issued by the Swedish Radiation Protection
Authority (SSI, formerly the Swedish Radiation Protection Institute)
(SSI FS 1998:1, ``Regulations on the Protection of Human Health and
the Environment in Connection with the Final Management of Spent
Nuclear Fuel and Nuclear Waste,'' Docket EPA-HQ-OAR-2005-0083-0047)
includes a numerical standard during the initial period after
disposal and adopts a more qualitative approach at later times.
Specifically, for the first 1,000 years following closure of a
repository, ``the assessment of the repository's protective
capability shall be based on quantitative analyses of the impact on
human health and the environment.'' (Section 11) Thus, initially the
performance projections may be used to make decisions regarding the
protectiveness of the disposal system. However, beyond the first
thousand years, ``the assessment of the repository's protective
capability shall be based on various possible sequences for the
development of the repository's properties, its environment and the
biosphere.'' (Section 12) Similarly, the Finnish Radiation and
Nuclear Safety Authority's (STUK) regulations for ``Long-term Safety
of Disposal of Spent Nuclear Fuel'' (YVL 8.4, May 2001, Docket EPA-
HQ-OAR-2005-0083-0392) include two primary protection standards. The
first is an individual-protection standard of 10 mrem/yr (0.1 mSv/
yr), which applies to ``an assessment period that is adequately
predictable with respect to assessments of human exposure but that
shall be extended to at least several thousands of years.'' (Section
2.2) The second protection standard, which is implied to cover
periods beyond the time for which ``human exposure'' is ``adequately
predictable,'' is a radionuclide release standard similar to that
included in 40 CFR part 191 and applied at WIPP. We also refer
readers to the French standard (Basic Safety Rule No. III.2.f,
``Disposal of Radioactive Waste in Deep Geological Formations,''
1991, Docket No. EPA-HQ-OAR-2005-0083-0389). For the initial period,
which is to last ``at least 10,000 years * * * The limit of [25
mrem/yr] will be applied for determining the acceptability of the
radiological consequences.'' However, ``[b]eyond this period'' when
``uncertainty concerning the evolution of the repository increases
progressively with time * * * Quantified estimates of the individual
dose estimates must then be made. These may be supplemented, by more
qualitative assessments of the results of these estimates, as
regards the geological barrier evolution factors, so as to verify
that the release of the radionuclides does not result in an
unacceptable individual dose. In this verification, the same [25
mrem/yr] limit shall be used as a reference value.'' (Section 3.2.1,
emphasis added)

---------------------------------------------------------------------------

2. What is the Dose Standard for 10,000 Years After Disposal?
    Section 801(a)(1) of the EnPA directs us to ``promulgate, by rule,
public health and safety standards'' that ``prescribe the maximum
annual effective dose equivalent to individual members of the public''
from releases of radioactive material from the Yucca Mountain
repository. Promulgation of the standard described in section III.A.1
of this document, which will apply beyond 10,000 years and up to 1
million years, fulfills this statutory direction. Today's final rule
also retains the standard promulgated in 2001 as Sec.  197.20, which
requires that DOE demonstrate a reasonable expectation that the RMEI
will not incur annual doses greater than 15 mrem from releases of
radionuclides from the Yucca Mountain disposal system for 10,000 years
after disposal. We believe this is an appropriate exercise of our
policy discretion, protective of public health and safety, and
consistent with our generic standards at 40 CFR part 191 (now applied
to the WIPP) and other applications in both our regulations for
hazardous materials and internationally for radioactive waste. Further,
this dose level is also within the range of risks identified by NAS as
consistent with current national and international regulations. (NAS
Report p. 49, Tables 2-3 and 2-3) Moreover, the 15 mrem/yr standard for
10,000 years is consistent with EPA's overall risk management policies
\16\ and serves as a logical foundation for us to incorporate concerns
regarding far future projections (such as the specifications regarding
seismic, igneous, and climatic events and processes discussed in
section III.B of this document).
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    \16\ The annual fatal cancer risk of 15 mrem is 8.6 x
10-6, based on a conversion factor of 5.75 x
10-4 fatal cancers per rem.
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    As we stated in our proposal, an important reason for retaining a
standard applicable for the first 10,000 years is to address the
possibility, however unlikely, that significant doses could occur
within 10,000 years, even if the peak dose occurs significantly later,
as NAS believed likely. (NAS Report p. 2) We received some comments
suggesting that DOE's estimates of waste package performance are overly
optimistic and that significant early package failures are possible, if
not to be expected. Some commenters incorrectly argued that we had
inappropriately ``ratified'' DOE's projections of waste package
performance and our proposal ``would provide essentially no protection
for the period before 10,000 years,'' because early failure of a system
licensed against a post-10,000-year dose standard in excess of 15 mrem/
yr would have greater consequences than would early failure of a system
licensed against a 15 mrem/yr standard that applied at all times. We
recognize that DOE's estimates of waste package integrity rely heavily
on extrapolations of laboratory testing data, which involve significant
uncertainties, especially when considering time frames well in excess
of all practical experience. It is not possible to claim unequivocally
that no information will come to light that might cause a reassessment
of the containers' behavior and its effect on disposal system
performance. However, while DOE must defend its estimates in licensing,
our rulemaking is not dependent on resolution of this issue. DOE will
have to demonstrate that there is a reasonable expectation that the
dose to the RMEI will not exceed 15 mrem/yr in the first 10,000 years
after closure. Thus, the addition of the peak dose standard in no way
weakens the protection provided by our 2001 standards, since disposal
system performance must still be assessed against the 15 mrem/yr limit
during the relevant time period.
    In fact, the reverse is true. The peak dose standard adds a new
level of public health protection for the post-10,000-year period that
was not defined in our 2001 standards. It may in fact be highly
unlikely, if not impossible, for projected doses to exceed (or even
approach) 15 mrem/yr within the first 10,000 years without also
exceeding 100 mrem/yr at some other time during the compliance period
(see section III.A.4, ``How Did We Consider Uncertainty and Reasonable
Expectation?''). In that case, the peak dose standard of 100 mrem/yr
alone would provide the necessary public health protection at all times
during the compliance period. The 10,000-year standard would not, then,
control projected doses during that period but would instead represent
an explicit statement of the level of performance that is required to
be achieved by the peak dose standard in that initial period. We
believe it is important to structure our regulations to make it clear
that the standard of protection at Yucca Mountain would not be less
than that provided for WIPP or the Greater Confinement Disposal
facility (GCD).\17\
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    \17\ GCD is a group of 120-feet deep boreholes, located within
the Nevada Test Site, which contain disposed transuranic wastes.
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3. How Do Our Standards Protect Public Health and Safety?
    The peak dose standard we are establishing today, 1 mSv/yr (100
mrem/yr), will protect public health and safety for the period beyond
10,000 years and up to 1 million years. This standard is consistent
with the public dose limit recommended by ICRP and widely adopted
internationally and nationally. Section 801(a)(1) of the EnPA directs
us to ``promulgate, by rule, public health and safety standards'' that
``prescribe the maximum annual effective dose equivalent to individual
members of the public'' from releases of radioactive material from the
Yucca Mountain repository. In promulgating these standards, we have
given special consideration to the EnPA mandate that our standards be
``based upon and consistent with'' the recommendations of the NAS,
which included setting a ``health-based individual standard'' ``that
sets a limit on risk to individuals of adverse health effects.'' (NAS
Report pp. 65 and 4) We understand this to mean that we should select
the standard based, in part, on the level of risk, although NAS
declined to recommend such a level. (NAS Report p. 49) We have chosen
to express the standard in terms of dose, for the reasons described in
our 2001 final rulemaking (66 FR 32085-32086). In that rulemaking, we
did consider both the NAS views on risk and EPA policies and precedents
in establishing the dose standard. The risk associated with the 15
mrem/yr standard applicable for the initial 10,000-year period is
consistent with both the Agency's overall risk management policies and
the suggested NAS ``starting point'' (NAS Report p. 49) The nominal
annual risk associated with the final peak dose standard of 100 mrem/
yr, 5.75 x 10-5, is comparable to the range of risks
represented by domestic and international standards that NAS suggested
for EPA to consider.\18\ This is a protective level of risk given the
extremely long time frames contemplated for this standard, and
reasonable in that it effectively addresses the associated uncertainty
in projecting doses for up to 1 million years. Given this fact and the
broad consensus regarding 100 mrem/yr as a protective public dose
limit, EPA finds that the dose standard of 100 mrem/yr, with its
associated risk, is protective of the RMEI over the period from 10,000

years to 1 million years, as required by the EnPA.
---------------------------------------------------------------------------

    \18\ This document focuses on annual risk rather than lifetime
risk because NAS identified annual risk as the appropriate metric,
although it did not recommend a particular risk level.
---------------------------------------------------------------------------

    The Agency believes it important to emphasize two aspects of this
decision. First, modeling of a complex system such as the Yucca
Mountain disposal system over such time frames involves significant
uncertainties in both the knowledge of characteristics of the site and
the conceptual representation of the processes contributing to release
and transport of radionuclides. The NAS recommendation has extended the
application of regulatory judgment beyond the period when substantially
complete containment might reasonably be provided, and through a period
during which complete loss of containment cannot be discounted. The
sequence and timing of scenarios resulting in waste package failure are
highly dependent on initial assumptions and are the most significant
factors in estimating the timing and magnitude of doses to the RMEI.
Dose projections involve extrapolation of assumptions, models, and data
over time periods much longer than those considered in other regulatory
contexts. Such projections therefore cannot be confirmed in the usual
sense (i.e., through measurements or monitoring), nor is it expected
that long-term maintenance of the repository will be performed. Such
considerations lead us to conclude that it would not be realistic to
demand that projections from such complex systems be readily
distinguishable from one another at the level of incremental risk
customarily addressed by the Agency in situations where results can be
confirmed, modeling is utilized on a more limited scale, or
institutional controls are more applicable.
    The Agency's second concern is the correlation of risk with health
detriment. NAS specifically framed its recommendation to establish a
risk standard in the context of health effects. (NAS Report pp. 4 and
65) In doing so, it explicitly extended the traditional reliance on
``present knowledge'' in the framing of performance assessments to
assume that future societies would not have eliminated radiation cancer
risks.\19\ (NAS Report p. 100) However, the reliance on risk to express
the results of long-term safety assessments has been approached more
cautiously, and it has primarily been viewed as a mechanism to
incorporate the likelihood of scenarios affecting potential exposures,
rather than as a direct measure of health impacts or as a firm
compliance criterion.\20\
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    \19\ Dose can be converted to risk by use of either
radionuclide-specific or overall conversion factors. The NAS
committee referred only to overall conversions (i.e., risk per rem),
which is the typical approach applied to dose standards when the
specific mix of radionuclides is not well-defined in advance. The
committee saw the direct use of risk as an advantage if the
relationship should change in the future through new research on
low-dose health effects, because the underlying risk could be viewed
as representing the level of societal acceptance of health impacts,
which the committee saw as less likely to change, whereas dose could
become further removed from this level of societal acceptance. (NAS
Report p. 64) In fact, we use a conversion factor slightly higher
than that cited by the NAS committee (5.75 x 10-4 fatal
cancers per rem, compared to the committee's figure of 5 x
10-4 per rem). See 66 FR 32080-32081, for more discussion
of health risks from ionizing radiation.
    \20\ For example, a 2007 NEA document on ``Consideration of
Timescales in Post-Closure Safety of Geological Disposal of
Radioactive Waste'' (NEA/RWMC/IGSC/(2006)3), which was based on
surveys of Member Countries, points out that ``In evaluating
compliance with regulatory criteria, or in formulating these
criteria, extreme scenarios or parameter distributions can generally
be assigned less weight. This is, for example, inherent in criteria
expressed in terms of risk.'' (Docket No. EPA-HQ-OAR-2005-0083-0411,
p. 38) Similarly, the UK Environment Agency has stated: ``In the
1995 White Paper, the Government stated that reliance cannot be
placed exclusively on estimates of risk to determine whether the
facility is safe. Whilst such calculations can inform a judgement on
the safety of the facility, other technical factors, including some
of a more qualitative nature, will also need to be considered. The
Government therefore considers it inappropriate to rely on a
specified risk limit or risk constraint as an acceptance criterion
for a disposal facility after control is withdrawn. It is, however,
considered appropriate to apply a risk target in the design
process.'' (Guidelines for Authorisation of Disposal Facilities for
Low- and Intermediate-Level Radioactive Waste, Docket No. EPA-HQ-
OAR-2005-0083-0063, Paragraph 6.14)
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    Risk correlations are highly dependent on population
characteristics and baseline cancer rates, which change over time with
dietary, lifestyle, medical, industrial, environmental, demographic,
and other contributing factors. ICRP has expressed caution that
``[d]oses and risks, as measures of health detriment, cannot be
forecast with any certainty for periods beyond around several hundreds
of years into the future * * * Such estimates must not be regarded as
predictions of future health detriment.'' However, ICRP has also
suggested that it is not unreasonable for shorter-term assessments to
relate dose or risk to health effects: ``To evaluate the performance of
waste disposal systems over long time scales, one approach is the
consideration of quantitative estimates of dose or risk on the order of
1000 to 10,000 years. This approach focuses on that period when the
calculation of doses most directly relates to health detriment * * *''
(ICRP Publication 81, ``Radiation Protection Recommendations as Applied
to the Disposal of Long-Lived Radioactive Waste,'' Docket No. EPA-HQ-
OAR-2005-0083-0417, Paragraphs 41 and 71, respectively) Thus, the
Agency finds that its requirements for the probabilistic calculation of
doses effectively incorporates the issue of risk as it has customarily
been considered in long-term safety assessments. Further, the Agency
believes its decision to view the 10,000-year standard within its
traditional risk-management framework is reasonable and consistent with
views on shorter-term safety assessments.
    The nominal annual risk level for fatal cancer associated with the
100 mrem/yr dose standard is 5.75 x 10-5. This is comparable
to the range of risks represented by national and international
regulations identified by NAS for EPA to consider, and is premised on a
dose level the NAS has addressed favorably as a matter of international
regulatory consensus (NAS Report pp. 40-41, Tables 2-3 and 2-4).
Considering that this standard will apply for up to 1 million years, we
believe this represents a level of risk that will protect public health
and safety in the far future. However, for the reasons described above,
we do not believe it is appropriate to view the standard through a
strict risk perspective, and caution against doing so. Further, even if
the risk correlations could be assumed valid over such times, the
nominal risk represented by projected doses may be a reflection of the
uncertainties inherent in such projections, and therefore overstated.
ICRP states, for example, that ``as the time frame increases, some
allowance should be made for assessed dose or risk exceeding the dose
or risk constraint * * * This must not be misinterpreted as a reduction
in the protection of future generations, and, hence, as a contradiction
of the principle of equity of protection, but rather as an adequate
consideration of the uncertainties associated with the calculated
results.'' (ICRP Publication 81, Docket No. EPA-HQ-OAR-2005-0083-0417,
Paragraph 77).
    As a result of these considerations, for a standard covering
periods up to 1 million years, the Agency believes it is more
appropriate to view protectiveness from a broader perspective. This
perspective must include consideration of the modeling issues discussed
earlier, as well as be cognizant of the regulatory context in which
dose projections will be presented. NRC's judgment of ``reasonable
expectation'' will not rely on a simple comparison of the mean
projected dose with the regulatory standard, but will encompass the
data, assumptions, and models underlying those projections, including
the sources and treatment of uncertainties and conservatisms. We are
also mindful that the post-10,000-year peak dose standard

covers an extremely wide time window, far beyond that for any previous
regulatory situation in this country, and that a peak mean dose could
be projected to occur at any point within that time span. Where the
precision and predictive capabilities of performance assessment models
diminish over such long times, we believe it is appropriate that NRC
``weigh how the scientific basis for analysis changes with time'' in
reaching its judgment (NAS Report pp. 30-31).
    In that context, the 100 mrem/yr public dose limit recommended by
ICRP and widely adopted by national and international organizations and
government agencies represents a key element of radiation protection
practice that can be applied to the estimation of potential future
exposures. It provides a standard for public protection today and, by
extension in the far future. This judgment reflects our view that the
selected level must take into account larger, less quantifiable factors
such as the uncertainties involved in projecting doses over 1 million
years and the meaning that can be assigned to such projections (both in
terms of their value as predictions of expected behavior of the
disposal system and in their correlation with health effects), as well
as the relative importance they should assume, in a regulatory context.
Having considered these factors, we conclude that the post-10,000-year
dose standard of 100 mrem/yr is protective of the RMEI. It must also be
emphasized that the 100 mrem/yr level applies to the RMEI, who is
described as a person whose location, lifestyle, and characteristics
cause that person to be subject to doses at the high end of the local
population. As a result, the RMEI is among the most highly exposed
members of the public. Most residents in the vicinity of Yucca Mountain
would receive much lower doses from the disposal system than the RMEI,
if any dose at all.
    Taken together, the dual standards provide a reasonable test of the
disposal system that appropriately combines protectiveness with
recognition of the limitations of modeling in predicting the evolution
of that system over hundreds of thousands of years. The 10,000-year
standard is solidly grounded in the Agency's risk-management framework
and prior practice for geologic disposal facilities. The longer-term
peak dose standard is widely-accepted domestically and internationally
as protective of public health and safety, reasonable in its
recognition of the regulatory context, and fulfills our EnPA mandate by
extending to the time of peak dose up to 1 million years. However, the
Agency also emphasizes the site-specific nature of this rulemaking,
which should not be viewed as a precedent for other regulatory
situations, but as a reasoned response to unique circumstances
involving issuance of a compliance standard applicable for periods up
to 1 million years after disposal.
4. How Did We Consider Uncertainty and Reasonable Expectation?
    In establishing our final standards pursuant to the EnPA, we have
considered two important statements from the NAS committee: (1) ``We
recognize that there are significant uncertainties in the supporting
calculations and that the uncertainties increase as the time at which
peak risk occurs increases'' and (2) ``No analysis of compliance will
ever constitute an absolute proof; the objective instead is a
reasonable level of confidence in analyses that indicates whether
limits established by the standard will be exceeded.'' (NAS Report pp.
56 and 71, respectively) We have been mindful of these statements, as
well as the fact that NAS deferred to our judgment in setting the level
of the final compliance standard, as indicating that there are limits
to the ability of science to provide definitive answers. ``When all
reasonable steps have been taken to reduce technical uncertainty * * *
there still remains a residual, unquantifiable uncertainty * * * The
only defense against it is to rely on informed judgment.'' (NAS Report
p. 80)
    We believe we have appropriately considered the NAS views in
establishing 1 mSv/yr (100 mrem/yr) as the individual-protection
standard for the period beyond 10,000 years and up to 1 million years.
In order to approve DOE's license application, NRC must determine, at a
minimum, that there is a reasonable expectation that standard will be
met (as well as determine compliance with other NRC requirements, such
as a multiple-barrier system). The primary indicator of compliance with
the individual-protection standard is the mean of the distribution of
projected doses presented by DOE (see Section III.A.9 of this document,
``How Will NRC Determine Compliance?''). However, NRC's compliance
determination will consist of more than a simple comparison of the mean
of projected doses with the dose standard. Rather, as stated in 40 CFR
197.14, NRC will reach its determination ``based upon the full record
before it.'' Regardless of whether the mean of projected doses is well
below the dose standard or not, NRC will examine the assumptions, data,
models, and other aspects of DOE's projections to ensure that it has an
understanding of those projections sufficient to reach a ``reasonable
expectation'' as to their compliance with the standard (40 CFR 197.13).
While applying the principles of reasonable expectation at all times,
NRC may also use its judgment as to whether it would apply the concept
in exactly the same way for times as long as 1 million years as it
would for much shorter times. A key element of reasonable expectation
is that it ``accounts for the inherently greater uncertainties in
making long-term projections of the performance of the Yucca Mountain
disposal system'' (Sec.  197.14(b)), we would consider it logical as
well as practical for NRC, in reaching its compliance decision, to
evaluate the sources and effects of uncertainties in DOE's analyses, as
well as DOE's treatment of them.\21\
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    \21\ ICRP Publication 81: ``Demonstration of compliance with the
radiological criteria is not as simple as a straightforward
comparison of calculated dose or risk with the constraints, but
requires a certain latitude of judgement.'' (Docket No. EPA-HQ-OAR-
2005-0083-0417, Paragraph 86)
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    Uncertainties can influence performance assessments in a number of
ways. Some sources of uncertainty can be addressed, or at least
accounted for, while in other areas our knowledge may be too limited to
even characterize the uncertainty, much less explicitly account for it.
Sources of uncertainty are often discussed in broad categories such as
``data'' or ``model'' uncertainty, although these can take on various
forms within those broader categories that create individual
challenges.\22\
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    \22\ For example, ``data'' uncertainty can cover broad issues
such as whether sufficient data are available, whether the right
kind of data are available, whether the data are of sufficient
quality, and whether the available data adequately capture what NAS