Implementation of a Dose Standard After 10,000 Years, 53313-53320 [05-17778]

Agencies

• NUCLEAR REGULATORY COMMISSION

[Federal Register Volume 70, Number 173 (Thursday, September 8, 2005)]
[Proposed Rules]
[Pages 53313-53320]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-17778]


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NUCLEAR REGULATORY COMMISSION

10 CFR Part 63

RIN 3150-AH68


Implementation of a Dose Standard After 10,000 Years

AGENCY: Nuclear Regulatory Commission.

ACTION: Proposed rule.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is proposing to 
amend its regulations governing the disposal of high-level radioactive 
wastes in a proposed geologic repository at Yucca Mountain, Nevada. The 
proposed rule would implement the U.S. Environmental Protection 
Agency's (EPA's) proposed standards for doses that could occur after 
10,000 years but within the period of geologic stability. The proposed 
rule also specifies a value to be used to represent climate change

[[Page 53314]]

after 10,000 years, as called for by EPA, and specifies that 
calculations of radiation doses for workers use the same weighting 
factors that EPA is proposing for calculating individual doses to 
members of the public.

DATES: The comment period expires November 7, 2005. Comments received 
after this date will be considered if it is practical to do so, but NRC 
is able to assure consideration only for comments received on or before 
this date.

ADDRESSES: You may submit comments by any one of the following methods. 
Please include the following number (RIN 3150-AH68) in the subject line 
of your comments. Comments on rulemakings submitted in writing or in 
electronic form will be made available to the public in their entirety 
on the NRC rulemaking Web site. Personal information will not be 
removed from your comments.
    Mail comments to: Secretary, U.S. Nuclear Regulatory Commission, 
Washington, DC 20555-0001, ATTN: Rulemakings and Adjudications Staff.
    E-mail comments to: SECY@nrc.gov. If you do not receive a reply e-
mail confirming that we have received your comments, contact us 
directly at (301) 415-1966. You may also submit comments via the NRC's 
rulemaking Web site at https://ruleforum.llnl.gov. Address questions 
about our rulemaking website to Carol Gallagher (301) 415-5905; e-mail 
cag@nrc.gov. Comments can also be submitted via the Federal eRulemaking 
Portal at https://www.regulations.gov.
    Hand deliver comments to: 11555 Rockville Pike, Rockville, Maryland 
20852, between 7:30 a.m. and 4:15 p.m. Federal workdays. (Telephone 
(301) 415-1966).
    Fax comments to: Secretary, U.S. Nuclear Regulatory Commission at 
(301) 415-1101.
    Publicly available documents related to this rulemaking may be 
examined and copied for a fee at the NRC's Public Document Room (PDR), 
Public File Area O1 F21, One White Flint North, 11555 Rockville Pike, 
Rockville, Maryland. Selected documents, including comments, can be 
viewed and downloaded electronically via the NRC rulemaking Web site at 
https://ruleforum.llnl.gov.
    Publicly available documents created or received at the NRC after 
November 1, 1999, are available electronically at the NRC's Electronic 
Reading Room at https://www.nrc.gov/NRC/ADAMS/. From this 
site, the public can gain entry into the NRC's Agencywide Document 
Access and Management System (ADAMS), which provides text and image 
files of NRC's public documents. If you do not have access to ADAMS or 
if there are problems in accessing the documents located in ADAMS, 
contact the NRC Public Document Room (PDR) Reference staff at 1-800-
397-4209, 301-415-4737, or by e-mail to pdr@nrc.gov.

FOR FURTHER INFORMATION CONTACT: Timothy McCartin, Office of Nuclear 
Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, 
Washington, DC 20555-0001, telephone (301) 415-7285, e-mail 
tjm3@nrc.gov; Janet Kotra, Office of Nuclear Material Safety and 
Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-
0001, telephone (301) 415-6674, e-mail jpk@nrc.gov; or Lydia Chang, 
Office of Nuclear Material Safety and Safeguards, U.S. Nuclear 
Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-
6319, e-mail lwc1@nrc.gov.

SUPPLEMENTARY INFORMATION:

I. Background

    On November 2, 2001 (66 FR 55732), NRC published its final rule, 10 
CFR part 63, governing disposal of high-level radioactive wastes in a 
potential geologic repository at Yucca Mountain, Nevada. The U.S. 
Department of Energy (DOE) must comply with these regulations for NRC 
to authorize construction and license operation of a potential 
repository at Yucca Mountain. As mandated by the Energy Policy Act of 
1992, Public Law 102-486 (EnPA), NRC's final rule was consistent with 
the radiation protection standards issued by EPA at 40 CFR Part 197 (66 
FR 32074; June 13, 2001). EPA developed these standards under Congress' 
direction, in Section 801 of EnPA, to issue public health and safety 
standards for protection of the public from releases of radioactive 
materials stored or disposed of in a potential repository at the Yucca 
Mountain site. These standards were to be ``based upon and consistent 
with'' the findings and recommendations of the National Academy of 
Sciences (NAS). The NAS issued its findings and recommendations, on 
August 1, 1995, in a report entitled Technical Bases for Yucca Mountain 
Standards.
    The State of Nevada and other petitioners challenged both the EPA 
standards and the NRC regulations in court. On July 9, 2004, the United 
States Court of Appeals for the District of Columbia Circuit upheld 
both EPA's standards and NRC's regulations on all but one of the issues 
raised by the petitioners. See Nuclear Energy Institute, Inc. v. 
Environmental Protection Agency, 373 F.3d 1251 (D.C. Cir. 2004). The 
court disagreed with EPA's decision to adopt a 10,000-year period for 
compliance with the standards and NRC's adoption of that 10,000-year 
compliance period in NRC's implementing regulations. The court found 
that EPA's 10,000-year compliance period was not ``based upon and 
consistent with'' NAS findings, as required by Section 801 of EnPA. See 
the aforementioned 373 F.3d at 1270. The NAS recommended that a 
standard be developed that would provide protection when radiation 
doses reach their peak within the limits imposed by long-term stability 
of the geologic environment. In addition, NAS found no scientific basis 
for limiting application of the individual-risk standard to 10,000 
years. Thus, the court vacated EPA's rule at 40 CFR part 197 to the 
extent that it specified a 10,000-year compliance period and remanded 
the matter to EPA. The court also vacated NRC's rule at 10 CFR Part 63 
insofar as it incorporated EPA's 10,000-year compliance period.
    In response to the remand, EPA issued its proposed revised 
standards on August 22, 2005 (70 FR 49014). To comply with EnPA and the 
court's remand, NRC must now revise 10 CFR Part 63 to be consistent 
with EPA's revised standards. For that purpose, NRC is proposing 
revisions to 10 CFR part 63 in this notice.

II. Discussion

    To address the court's decision, EPA is retaining the standards 
applicable to the first 10,000 years after disposal and proposes to add 
separate requirements for the peak dose after 10,000 years and within 
the period of geologic stability. EPA also proposes to revise the 
approach for calculating doses, based on International Commission on 
Radiological Protection (ICRP) recommendations, for the periods before 
and after 10,000 years. Specifically, EPA's proposed revisions to its 
standards: (1) Provide a limit for the peak dose after 10,000 years; 
(2) specify criteria DOE must use in performance assessments for 
estimating doses after 10,000 years; and (3) specify ``weighting 
factors'' for DOE's use when calculating individual dose during the 
operational or preclosure phase as well as after the disposal or 
postclosure phase. Also, in its proposal, EPA states that NRC should 
specify a value or values that DOE must use to represent climate change 
after 10,000 years.
    In this rulemaking, the NRC proposes to (1) adopt the limit EPA 
sets for the peak dose after 10,000 years; (2) adopt the criteria EPA 
has specified for performance assessments that estimate

[[Page 53315]]

doses after 10,000 years; (3) adopt the ``weighting factors'' EPA 
specifies for calculating individual doses during the operational or 
preclosure phase, as well as after the disposal or postclosure phase; 
(4) require that calculations of radiation doses for workers use the 
same weighting factors EPA is proposing for calculating individual 
dose; and (5) specify a value that DOE must use to project the long-
term impact of climate variation after 10,000 years, as called for by 
EPA. These proposals are more fully described below.
    The NRC's proposal of these changes to part 63 coincides with EPA's 
publication of its proposal to provide important and timely information 
to the public on how NRC plans to incorporate and implement EPA's 
standards in NRC's regulations. In general, the changes to part 63 
adopt the same or approximately the same wording as used by EPA in its 
proposed revisions to 40 CFR part 197. Comments on EPA's proposal 
(e.g., the dose limit) should be directed to EPA and refer to EPA's 
proposal published on August 22, 2005. NRC's existing regulations, 
which are applicable for the first 10,000 years after disposal, remain 
in place [e.g., the 0.15 millisieverts/year (15 millirem/year) 
individual protection standard] consistent with the existing EPA 
standards, and are not affected by this rulemaking except insofar as 
NRC's rule adopts more up-to-date dosimetry for dose calculations.
    The Commission welcomes comments on NRC's proposed implementation 
of EPA's proposed revisions to its standards as well as on NRC's 
revisions for use of specific weighting factors for calculating worker 
doses, and on NRC's specification of a value for climate change. NRC 
requests and will respond to comments only on those provisions of part 
63 that we are now proposing to change. A description of these changes 
follows.

1. Dose Limit

    EPA's proposed standards would require DOE to estimate peak dose 
after 10,000 years as part of the evaluations for both individual 
protection and human intrusion. DOE must then compare the results of 
these estimates to an annual dose limit of 3.5 mSv/yr (350 mrem/yr). 
For this comparison, EPA proposes that DOE use the median value of the 
projected doses after 10,000 years and through the period of geologic 
stability. NRC proposes to incorporate the new EPA dose limit and 
statistical measure for compliance directly into NRC's regulations at 
Sec.  63.311 for individual protection and at Sec.  63.321 for human 
intrusion.

2. Criteria for Performance Assessments Used to Estimate Peak Dose 
After 10,000 Years

    EPA proposes using the performance assessment for the first 10,000 
years as the basis for projecting repository performance after 10,000 
years. EPA asserts that its requirements for the performance assessment 
for the first 10,000 years (e.g., consideration for features, events, 
and processes with a probability of occurrence greater than 
10-\8\ per year) provide a suitable basis for projecting 
performance after 10,000 years. NRC's existing regulations at 10 CFR 
Part 63 already include additional requirements, governing the 
preparation of the performance assessment, that ensure that features, 
events, and processes considered for inclusion in the performance 
assessment over the 10,000-year compliance period represent a wide 
range of both favorable and detrimental effects on performance.
    Because of the uncertainties associated with estimating performance 
over very long times (e.g., hundreds of thousands of years) and to 
limit speculation, EPA proposes specific constraints on the 
consideration of features, events, and processes after 10,000 years. 
First, EPA asserts that data and models used to prepare the performance 
assessment for the first 10,000 years provide adequate support for 
projections used in the performance assessment after 10,000 years. For 
example, DOE may apply the seismic hazard curves used in the 10,000-
year assessment to project seismic activity after 10,000 years. Second, 
EPA proposes to (1) limit the analysis of seismic activity to the 
effects caused by damage to the drifts and the waste package; (2) limit 
analysis of igneous activity to effects on the waste package that 
result in release of radionuclides to the atmosphere or ground water; 
(3) limit the effect of climate variation to those resulting from 
increased water flowing to the repository; and (4) require DOE to 
include general corrosion in its analysis of engineered barrier 
performance. NRC proposes to incorporate these criteria into NRC 
regulations at Sec.  63.342. NRC also proposes revising requirements 
for the performance assessment, specified at Sec.  63.114, to be 
consistent with EPA's proposal that the performance assessment for the 
first 10,000 years serve as the basis for projecting repository 
performance assessment after 10,000 years.

3. Individual Dose Calculations

    EPA proposes that DOE use specific weighting factors provided in 
proposed Appendix A of its standards at 40 CFR 197. These weighting 
factors reflect current methods of dosimetry and updated models for 
calculating individual exposures from radiation. EPA cites, as a basis 
for this proposal, recommendations and guidance from ICRP Publications 
60 through 72. NRC supports the use of current dosimetry and proposes 
to adopt this specification.

4. Worker Dose Calculations

    Consistent with EPA's specification of dosimetry for calculating 
individual doses to members of the public (public doses), NRC proposes 
to revise its part 63 regulations to allow DOE to use the same methods 
for calculating doses to workers during the operational period as those 
required for calculating public doses. NRC believes that calculations 
of doses to workers and the public should rely on a single set of 
weighting factors, based on current dosimetry. This approach would 
avoid the unnecessary complication and potential confusion for 
stakeholders that could result from the use of two sets of weighting 
factors. NRC proposes to add a definition for ``weighting factor'' to 
Sec.  63.2 that specifies the weighting factors provided in the EPA 
proposal, and to amend Sec.  63.111(a)(1) to provide that calculation 
of doses to meet the requirements of 10 CFR part 20 shall use the 
definition for ``weighting factor'' in Sec.  63.2. Calculation of both 
worker and public doses would use the weighting factor as defined.

5. Values Used To Project Climate Variation After 10,000 Years

    EPA proposes that DOE should assume that the effect of climate 
variation, after 10,000 years, is limited to the results of increased 
water flowing through the repository. EPA also proposes that NRC 
specify, in regulation, steady-state (constant-in-time) values that DOE 
should use to project the long-term impact of climate variation after 
10,000 years. This approach focuses on ``average'' climate conditions 
over the long term rather than on time-varying aspects of climate 
(e.g., timing, size, and duration of short-term variations) that can be 
both uncertain and speculative. The NRC has considered what parameter 
or parameters would represent the average climate conditions. 
Precipitation and temperature are the most readily identified 
parameters, associated with climate, that directly influence the amount 
of water, or deep percolation, flowing to the repository horizon. It is 
the rate of deep percolation, however, that directly influences 
repository performance. Therefore, the NRC proposes to specify use of 
the deep

[[Page 53316]]

percolation rate to represent the effect of future climate in 
performance assessments after 10,000 years.
    Southern Nevada has experienced significant variation in mean 
annual precipitation and temperature over the past 1 to 3 million years 
(Forester, R. M. ``Pliocene-Climate History of the Western United 
States Derived from Lacustrine Ostracodes,'' Quaternary Science 
Reviews, Volume 10, pages 133-146, 1991). Estimates of future climate 
over the next 1 million years involve many assumptions and are 
uncertain. One approach, discussed when NRC issued its regulations for 
Yucca Mountain at 10 CFR part 63 (page 66 FR 55757; November 2, 2001), 
is to assume that fundamental mechanisms that will change the future 
climate will be the same as those that changed it in the past. 
Paleoclimate data suggest that, in general, over the past 1 million 
years, Southern Nevada has been cooler and wetter than it is today 
(Thompson, R. S., K. H. Anderson, and P. J. Bartlein, ``Quantitative 
Paleoclimatic Reconstructions from Late Pleistocene Plant Macrofossils 
of the Yucca Mountain Region,'' U.S. Geological Survey Open-File Report 
99-338, U.S. Geological Survey, Denver, CO, 1999; and Reheis, M., 
``Highest Pluvial Lake Shorelines and Pleistocene Climate in the 
Western Great Basin,'' Quaternary Research, Volume 52, pages 196-205, 
1999). Thus, NRC expects ``average'' conditions 10,000 years in the 
future, and later, to be cooler and wetter. Those conditions will allow 
more water to percolate to the repository horizon than expected during 
the first 10,000 years.
    According to climatologists, the so-called intermediate and monsoon 
climate states, which occur between the warmer ``interglacial'' and the 
cooler ``full glacial'' climate states, are both wetter than the 
present climate state. Climatologists estimate a mean annual 
precipitation, during these climate states, at about twice that of 
present mean annual precipitation at Yucca Mountain. Over the past 
million years, these two wetter climate states were the predominate 
climate states (Civilian Radioactive Waste Management System, 
Management and Operating Contractor, ``Future Climate Analysis--10,000 
years to 1,000,000 Years After Present,'' MOD-01-001 Rev. 00, 2002). To 
the extent that climate is controlled by changes in solar radiation 
arising from variations in the Earth's orbit [op. cit.], it is 
reasonable to assume that climate patterns during the next 1 million 
years would follow a similar cycle. Deep percolation rates depend on 
both precipitation and temperature and their associated effects on 
evaporation and plant transpiration. Today, the mean precipitation, 
measured at Yucca Mountain, is 125 millimeters/year (mm/year) (4.9 
inches/year) (Thompson, R. S., K. H. Anderson, and P. J. Bartlein, 
``Quantitative Paleoclimatic Reconstructions from Late Pleistocene 
Plant Macrofossils of the Yucca Mountain Region,'' U.S. Geological 
Survey Open-File Report 99-338, U.S. Geological Survey, Denver, CO, 
1999). About 4 percent of that water reaches the repository horizon. 
This corresponds to an estimated deep percolation rate of 5 mm/year 
(0.20 inches/year) when averaged over the repository footprint (Zhu, 
C., J. R. Winterle, and E. I. Love, ``Late Pleistocene and Holocene 
Groundwater Recharge from the Chloride Mass Balance Method and 
Chlorine-36 Data,'' Water Resources Research, Vol 39, No. 7, page 1182, 
2003). Examination of locations in the United States, analogous to 
Yucca Mountain in some future intermediate and monsoon climates, 
suggests potential precipitation rates of between 266 and 321 mm/year 
[10.5 and 12.6 inches/year] (Thompson, R. S., K. H. Anderson, and P. J. 
Bartlein, ``Quantitative Paleoclimatic Reconstructions from Late 
Pleistocene Plant Macrofossils of the Yucca Mountain Region,'' U.S. 
Geological Survey Open-File Report 99-338, U.S. Geological Survey, 
Denver, CO, 1999).
    Estimates of deep percolation rate as a fraction of precipitation 
have been calculated for various climate conditions. Between 5 to 20 
percent of precipitation could reach the repository depth under 
intermediate/monsoon to ``full glacial'' climate conditions. The larger 
percentage reflects ``full glacial'' conditions (Mohanty, S., R. 
Codell, J. M. Menchaca, et al., System-Level Performance Assessment of 
the Proposed Repository at Yucca Mountain Using the TPA Version 4.1 
Code, CNWRA 2002-05 Revision 2, Center for Nuclear Waste Regulatory 
Analyses, San Antonio, TX, 2004). Given that average deep percolation 
at Yucca Mountain is about 4 percent of precipitation, under current 
conditions, and assuming between 5 to 20 percent for the fraction of 
precipitation that remains as deep percolation under intermediate/
monsoon climates, one may estimate higher average water flow to the 
repository than observed today. On this basis, the NRC proposes that 
DOE represent the effects of climate change after 10,000 years by 
assuming that deep percolation rates vary between 13 to 64 mm/year (0.5 
to 2.5 inches/year) \1\. DOE would implement this assumption in its 
performance assessment by sampling values of deep percolation rates 
within this range, and, for a given calculation, by assuming the deep 
percolation rate remained constant, at the sampled rate, after 10,000 
years.
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    \1\ The low value of the range is derived using the lower 
estimated fraction of precipitation that results in deep percolation 
and the lower precipitation rate (i.e., 5 percent of 266 is 
approximately 13) and the high value of the range from using the 
higher estimated fraction of precipitation that results in deep 
percolation and the higher value for precipitation rate (i.e., 20 
percent of 321 is approximately 64).
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    Thus, NRC proposes that DOE use a time-independent deep percolation 
rate, after 10,000 years, based on a log uniformly distributed range of 
deep percolation rates from 13 to 64 mm/year (0.5 to 2.5 inches/year). 
This ``average'' deep percolation rate represents the average amount of 
water flowing to the repository horizon. Specifying a rate that is 
constant over time, however, does not imply that this same rate should 
necessarily be held constant spatially over the entire repository 
horizon. To the contrary, current understanding of site behavior (e.g., 
NRC staff and DOE staff representations of infiltration and percolation 
processes at Yucca Mountain) shows significant variation in current 
deep percolation rates across the repository horizon. This would be 
expected to continue to occur into the far future. NRC expects DOE to 
continue such calculations of spatial variation, subject to the 
constraint that, across the repository footprint, the ``average'' 
overall percolation rate would remain within the range and distribution 
specified by NRC.
    The Commission considers it appropriate to specify these 
constraints on how DOE must account for the effects of climate change 
during the period after 10,000 years because this approach: (1) Is 
consistent with EPA's proposal for treatment of climate change after 
10,000 years; (2) specifies, in a straightforward way, how DOE shall 
represent climate change in its performance assessment; (3) results in 
a mean deep percolation rate of approximately 32 mm/year \2\ (1.3 
inches/year), a rate that is approximately six times greater than the 
current rate, representing wetter and cooler conditions (e.g., 
interglacial and monsoon climate states); and (4) provides information 
on the relative significance of the deep percolation rate

[[Page 53317]]

(e.g., results of the performance assessment when the deep percolation 
rate is assumed to be at the low value of the range versus the high 
value of the range).
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    \2\ The mean value of a log-uniform distribution of deep 
percolation that ranges from 13 mm/year to 64 mm/yr is equal to (64 
mm/year -13 mm/year)/[loge(64 mm/year) -
loge(13 mm/year)] = 32 mm/year.
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III. Discussion of Proposed Amendments by Section

Section 63.2s Definitions

    This section would be modified to revise the definition of 
``performance assessment'' to exclude the limitation of ``10,000 years 
after disposal,'' consistent with EPA's modified definition of 
``performance assessment.'' This section also would be modified to 
include a definition for ``weighting factor'' that conforms the 
weighting factors to be used in dose calculations to the values EPA 
proposes.

Section 63.111 Performance Objectives for the Geologic Repository 
Operations Area Through Permanent Closure

    This section specifies requirements for radiation exposures for the 
geologic repository operations area. This section would be modified to 
require use of the definition for ``weighting factor'' in Sec.  63.2 
when calculating doses to meet the requirements of part 20 of this 
chapter.

Section 63.114 Requirements for Performance Assessment

    This section specifies the requirements for the performance 
assessment used to demonstrate compliance with the requirements 
specified at Sec.  63.113(b), (c), and (d). This section would be 
revised to conform to EPA's proposed standards that specify what DOE 
must consider in the performance assessment for the period after 10,000 
years.

Section 63.302 Definitions for Subpart L

    The definition for the ``period of geologic stability'' would be 
modified to clarify that this period ends at 1 million years after 
disposal.

Section 63.303 Implementation of Subpart L

    This section provides a functional overview of this subpart. This 
section would be revised to conform to EPA's proposed standard that 
specifies the arithmetic mean of the projected doses to be used for 
determining compliance for the period within 10,000 years after 
disposal and the median value of the projected doses to be used for 
determining compliance for the period after 10,000 years and through 
the period of geologic stability.

Section 63.305 Required Characteristics of the Reference Biosphere

    This section specifies characteristics of the reference biosphere 
to be used by DOE in its performance assessments to demonstrate 
compliance with the requirements specified at Sec.  63.113. This 
section would be modified to conform to EPA's proposed standards, which 
specify the types of changes DOE shall account for in the performance 
assessment for the period after 10,000 years and through the period of 
geologic stability.

Section 63.311 Individual Protection Standard After Permanent Closure

    This section specifies the dose limit for individual protection 
after permanent closure for any geologic repository at the Yucca 
Mountain site. This section would be modified to conform with the 
public health and environmental radiation standards EPA proposes for 
the peak dose after 10,000 years and through the period of geologic 
stability.

Section 63.321 Individual Protection Standard for Human Intrusion

    This section directs DOE to estimate the dose resulting from a 
stylized human intrusion drilling scenario and specifies the dose limit 
that any geologic repository at the Yucca Mountain site must meet as 
the result of a hypothetical human intrusion. This section would be 
modified to conform with the public health and environmental radiation 
standards EPA proposes for the peak dose after 10,000 years and through 
the period of geologic stability.

Section 63.341 Projections of Peak Dose

    This section has been removed.

Section 63.342 Limits on Performance Assessments

    This section specifies how DOE will identify and consider features, 
events, and processes in the dose assessments described in subpart L to 
part 63. This section would be modified to conform to EPA's proposed 
standards, which specify the types of changes DOE shall account for in 
the performance assessment for the period after 10,000 years and 
through the period of geologic stability. A range of values has been 
specified that DOE shall use to represent the effects of climate change 
after 10,000 years and through the period of geologic stability.

IV. Agreement State Compatibility

    Under the ``Policy Statement on Adequacy and Compatibility of 
Agreement State Programs'' approved by the Commission on June 30, 1997, 
and published in the Federal Register on September 3, 1997 (62 FR 
46517), this rule is classified as Compatibility Category ``NRC.'' 
Compatibility is not required for Category ``NRC'' regulations. The NRC 
program elements in this category are those that relate directly to 
areas of regulation reserved to the NRC by the Atomic Energy Act of 
1954, as amended (AEA), or the provisions of Title 10 of the Code of 
Federal Regulations. An Agreement State may not adopt program elements 
reserved to NRC.

V. Plain Language

    The Presidential memorandum, dated June 1, 1998, entitled, ``Plain 
Language in Government Writing,'' directed that the Government's 
writing be in plain language. This memorandum was published on June 10, 
1998 (63 FR 31883). NRC requests comments on this proposed rule 
specifically with respect to the clarity and effectiveness of the 
language used. Comments should be sent to the address listed under the 
heading of ADDRESSES, above.

VI. Voluntary Consensus Standards

    The National Technology Transfer and Advancement Act of 1995 (Pub. 
L. 104-113) requires that Federal agencies use technical standards that 
are developed or adopted by voluntary consensus standards bodies unless 
the use of such a standard is inconsistent with applicable law or 
otherwise impractical. In this proposed rule, NRC would implement site-
specific standards proposed by EPA and developed solely for application 
to a proposed geologic repository for high-level radioactive waste at 
Yucca Mountain, Nevada. This action does not constitute the 
establishment of a standard that establishes generally applicable 
requirements.

VII. Finding of No Significant Environmental Impact: Availability

    Pursuant to Section 121(c) of the Nuclear Waste Policy Act, this 
proposed rule does not require the preparation of an environmental 
impact statement under Section 102(2)(c) of the National Environmental 
Policy Act of 1969 or any environmental review under subparagraph (E) 
or (F) of Section 102(2) of such act.

VIII. Paperwork Reduction Act Statement

    This proposed rule does not contain new or amended information 
collection requirements subject to the Paperwork Reduction Act of 1995 
(44 U.S.C. 3501

[[Page 53318]]

et seq.). Existing requirements were approved by the Office of 
Management and Budget (OMB), approval number 3150-0199.

Public Protection Notification

    NRC may not conduct nor sponsor, and a person is not required to 
respond to, a request for information nor an information collection 
requirement, unless the requesting document displays a currently valid 
OMB control number.

IX. Regulatory Analysis

    The Commission has prepared a draft regulatory analysis on this 
proposed regulation. The analysis examines the costs and benefits of 
the alternatives considered by the Commission, consistent with the 
options that are open to NRC in carrying out the statutory directive of 
EnPA. The Commission requests public comment on the draft regulatory 
analysis. Comments on the draft analysis may be submitted to NRC, as 
indicated under the ADDRESSES, heading. The analysis is available for 
inspection in the NRC PDR, 11555 Rockville Pike, Rockville, MD 20852. 
Single copies of the regulatory analysis may be obtained from Lydia 
Chang, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear 
Regulatory Commission, Washington, DC 20555-0001, telephone (301) 415-
6319, e-mail lwc1@nrc.gov.

X. Regulatory Flexibility Certification

    In accordance with the Regulatory Flexibility Act of 1980 [5 U.S.C. 
605(b)], NRC certifies that this proposed rule will not, if issued, 
have a significant economic impact on a substantial number of small 
entities. This proposed rule affects only the licensing of one entity, 
DOE, which does not fall within the scope of the definition of ``small 
entities'' set forth in the Regulatory Flexibility Act nor the Small 
Business Size Standards set out in regulations issued by the Small 
Business Administration at 13 CFR part 121.

XI. Backfit Analysis

    NRC has determined that the backfit rule (Sec. Sec.  50.109, 70.76, 
72.62, or 76.76) does not apply to this proposed rule because this 
amendment would not involve any provisions that would impose backfits, 
as defined in the backfit rule. Therefore, a backfit analysis is not 
required.

List of Subjects in 10 CFR Part 63

    Criminal penalties, High-level waste, Nuclear power plants and 
reactors, Reporting and recordkeeping requirements, Waste treatment and 
disposal.

    For the reasons set out in the preamble and under the authority of 
the Atomic Energy Act of 1954, as amended; the Energy Reorganization 
Act of 1974, as amended; the Nuclear Waste Policy Act of 1982, as 
amended; and 5 U.S.C. 553, the NRC is proposing to adopt the following 
amendments to 10 CFR part 63.

PART 63--DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN A GEOLOGIC 
REPOSITORY AT YUCCA MOUNTAIN, NEVADA

    1. The authority citation for part 63 continues to read as follows:

    Authority: Secs. 51, 53, 62, 63, 65, 81, 161, 182, 183, 68 Stat. 
929, 930, 932, 933, 935, 948, 953, 954, as amended (42 U.S.C. 2071, 
2073, 2092, 2093, 2095, 2111, 2201, 2232, 2233); secs. 202, 206, 88 
Stat.1244, 1246 (42 U.S.C. 5842, 5846); secs. 10 and 14, Pub. L. 95-
601, 92 Stat. 2951 (42 U.S.C. 2021a and 5851); sec. 102, Pub. L. 91-
190, 83 Stat. 853 (42 U.S.C. 4332); secs. 114, 121, Pub. L. 97-425, 
96 Stat. 2213g, 2238, as amended (42 U.S.C. 10134, 10141); and Pub. 
L. 102-486, sec. 2902, 106 Stat. 3123 (42 U.S.C. 5851); sec. 1704, 
112 stat. 2750 (44 U.S.C. 3504 note).

    2. Section 63.2 is amended by revising paragraph (1) of the 
definition of ``performance assessment'' and by adding a new definition 
for ``weighting factor,'' in alphabetical order, to read as follows:


Sec.  63.2  Definitions.

* * * * *
    Performance assessment means an analysis that:
    (1) Identifies the features, events, processes (except human 
intrusion), and sequences of events and processes (except human 
intrusion) that might affect the Yucca Mountain disposal system and 
their probabilities of occurring;
* * * * *
    Weighting factor for an organ or tissue is the proportion of the 
risk of stochastic effects resulting from irradiation of that organ or 
tissue to the total risk of stochastic effects when the whole body is 
irradiated uniformly. For calculating the effective dose equivalent, 
the values in Appendix A of 40 CFR part 197 are to be used.
    3. In Sec.  63.111, paragraph (a)(1) is revised to read as follows:


Sec.  63.111  Performance objectives for the geologic repository 
operations area through permanent closure.

    (a) * * *
    (1) The geologic repository operations area must meet the 
requirements of part 20 of this chapter. Calculation of doses to meet 
the requirements of part 20 of this chapter shall use the definition 
for ``weighting factor'' in Sec.  63.2.
* * * * *
    4. Section 63.114 is revised to read as follows:


Sec.  63.114  Requirements for performance assessment.

    (a) Any performance assessment used to demonstrate compliance with 
Sec.  63.113 for 10,000 years after disposal must:
    (1) Include data related to the geology, hydrology, and 
geochemistry (including disruptive processes and events) of the Yucca 
Mountain site, and the surrounding region to the extent necessary, and 
information on the design of the engineered barrier system used to 
define, for 10,000 years after disposal, parameters and conceptual 
models used in the assessment.
    (2) Account for uncertainties and variabilities in parameter 
values, for 10,000 years after disposal, and provide for the technical 
basis for parameter ranges, probability distributions, or bounding 
values used in the performance assessment.
    (3) Consider alternative conceptual models of features and 
processes, for 10,000 years after disposal, that are consistent with 
available data and current scientific understanding and evaluate the 
effects that alternative conceptual models have on the performance of 
the geologic repository.
    (4) Consider only features, events, and processes consistent with 
the limits on performance assessment specified at Sec.  63.342.
    (5) Provide the technical basis for either inclusion or exclusion 
of specific features, events, and processes in the performance 
assessment. Specific features, events, and processes must be evaluated 
in detail if the magnitude and time of the resulting radiological 
exposures to the reasonably maximally exposed individual, or 
radionuclide releases to the accessible environment, for 10,000 years 
after disposal, would be significantly changed by their omission.
    (6) Provide the technical basis for either inclusion or exclusion 
of degradation, deterioration, or alteration processes of engineered 
barriers in the performance assessment, including those processes that 
would adversely affect the performance of natural barriers. 
Degradation, deterioration, or alteration processes of engineered 
barriers must be evaluated in detail if the magnitude and time of the 
resulting radiological exposures to the reasonably maximally exposed 
individual, or radionuclide releases to the accessible

[[Page 53319]]

environment, for 10,000 years after disposal, would be significantly 
changed by their omission.
    (7) Provide the technical basis for models used to represent the 
10,000 years after disposal in the performance assessment, such as 
comparisons made with outputs of detailed process-level models and/or 
empirical observations (e.g., laboratory testing, field investigations, 
and natural analogs).
    (b) Any performance assessment used to demonstrate compliance with 
Sec.  63.113 for the period of time after 10,000 years through the 
period of geologic stability must be based on the performance 
assessment specified in paragraph (a) of this section.
    5. In Section 63.302, the definition of ``period of geologic 
stability'' is revised to read as follows:


Sec.  63.302  Definitions for Subpart L.

* * * * *
    Period of geologic stability means the time during which the 
variability of geologic characteristics and their future behavior in 
and around the Yucca Mountain site can be bounded, that is, they can be 
projected within a reasonable range of possibilities. This period is 
defined to end at 1 million years after disposal.
* * * * *
    6. Section 63.303 is revised to read as follows:


Sec.  63.303  Implementation of Subpart L.

    (a) Compliance is based upon the arithmetic mean of the projected 
doses from DOE's performance assessments for the period within 10,000 
years after disposal for:
    (1) Sec.  63.311(a)(1); and
    (2) Sec. Sec.  63.321(b)(1) and 63.331, if performance assessment 
is used to demonstrate compliance with either or both of these 
sections.
    (b) Compliance is based upon the median of the projected doses from 
DOE's performance assessments for the period after 10,000 years of 
disposal and through the period of geologic stability for:
    (1) Sec.  63.311(a)(2); and
    (2) Sec.  63.321(b)(2), if performance assessment is used to 
demonstrate compliance.
    7. Section 63.305, paragraph (c) is revised to read as follows:


Sec.  63.305  Required characteristics of the reference biosphere.

* * * * *
    (c) DOE must vary factors related to the geology, hydrology, and 
climate based upon cautious, but reasonable assumptions consistent with 
present knowledge of factors that could affect the Yucca Mountain 
disposal system during the period of geologic stability and consistent 
with the requirements for performance assessments specified at Sec.  
63.342.
* * * * *
    8. Section 63.311 is revised to read as follows:


Sec.  63.311  Individual protection standard after permanent closure.

    (a) DOE must demonstrate, using performance assessment, that there 
is a reasonable expectation that the reasonably maximally exposed 
individual receives no more than the following annual dose from 
releases from the undisturbed Yucca Mountain disposal system:
    (1) 0.15 mSv (15 mrem) for 10,000 years following disposal; and
    (2) 3.5 mSv (350 mrem) after 10,000 years, but within the period of 
geologic stability.
    (b) DOE's performance assessment must include all potential 
environmental pathways of radionuclide transport and exposure.
    9. Section 63.321 is revised to read as follows:


Sec.  63.321  Individual protection standard for human intrusion.

    (a) DOE must determine the earliest time after disposal that the 
waste package would degrade sufficiently that a human intrusion (see 
Sec.  63.322) could occur without recognition by the drillers.
    (b) DOE must demonstrate that there is a reasonable expectation 
that the reasonably maximally exposed individual receives, as a result 
of human intrusion, no more than the following annual dose:
    (1) 0.15 mSv (15 mrem) for 10,000 years following disposal; and
    (2) 3.5 mSv (350 mrem) after 10,000 years, but within the period of 
geologic stability.
    (c) DOE's analysis must include all potential environmental 
pathways of radionuclide transport and exposure, subject to the 
requirements at Sec.  63.322.


Sec.  63.341  [Removed]

    10. Section 63.341 is removed.
    11. Section 63.342 is revised to read as follows:


Sec.  63.342  Limits on performance assessments.

    (a) DOE's performance assessments conducted to show compliance with 
Sec. Sec.  63.311(a)(1), 63.321(b)(1), and 63.331 shall not include 
consideration of very unlikely features, events, or processes, i.e., 
those that are estimated to have less than one chance in 10,000 of 
occurring within 10,000 years of disposal (less than one chance in 
100,000,000 per year). In addition, DOE's performance assessments need 
not evaluate the impacts resulting from any features, events, and 
processes or sequences of events and processes with a higher chance of 
occurrence if the results of the performance assessments would not be 
changed significantly in the initial 10,000 year period after disposal.
    (b) For performance assessments conducted to show compliance with 
Sec. Sec.  63.321(b) and 63.331, DOE's performance assessments shall 
exclude the unlikely features, events, and processes, or sequences of 
events and processes, i.e., those that are estimated to have less than 
one chance in 10 and at least one chance in 10,000 of occurring within 
10,000 years of disposal (less than one chance in 100,000 per year and 
at least one chance in 100,000,000 per year).
    (c) For performance assessments conducted to show compliance with 
Sec. Sec.  63.311(a)(2) and 63.321(b)(2), DOE's performance assessments 
shall project the continued effects of the features, events, and 
processes included in paragraph (a) of this section beyond the 10,000 
year post-disposal period through the period of geologic stability. DOE 
must evaluate all of the features, events, or processes included in 
paragraph (a) of this section, and also:
    (1) DOE must assess the effects of seismic and igneous scenarios 
subject to the probability limits in paragraph (a) of this section for 
very unlikely features, events, and processes. Performance assessments 
conducted to show compliance with Sec.  63.321(b)(2) are also subject 
to the probability limits in paragraph (b) of this section for unlikely 
features, events, and processes.
    (i) The seismic analysis may be limited to the effects caused by 
damage to the drifts in the repository and failure of the waste 
package.
    (ii) The igneous analysis may be limited to the effects of a 
volcanic event directly intersecting the repository. The igneous event 
may be limited to that causing damage to the waste packages directly, 
causing releases of radionuclides to the biosphere, atmosphere, or 
ground water.
    (2) DOE must assess the effects of climate change. The climate 
change analysis may be limited to the effects of increased water flow 
through the repository as a result of climate change, and the resulting 
transport and release of radionuclides to the accessible environment. 
The nature and degree of climate change may be represented by constant 
climate conditions. The analysis may commence at 10,000 years after 
disposal and shall extend to the

[[Page 53320]]

period of geologic stability. The constant value to be used to 
represent climate change is to be based on a log-uniform probability 
distribution for deep percolation rates from 13 to 64 mm/year (0.5 to 
2.5 inches/year).
    (3) DOE must assess the effects of general corrosion on the 
engineered barriers. DOE may use a constant representative corrosion 
rate throughout the period of geologic stability or a distribution of 
corrosion rates correlated to other repository parameters.

    Dated at Rockville, Maryland, this 1st day of September, 2005.

    For the Nuclear Regulatory Commission.
Annette Vietti-Cook,
Secretary of the Commission.
[FR Doc. 05-17778 Filed 9-7-05; 8:45 am]
BILLING CODE 7590-01-P