[Federal Register Volume 90, Number 167 (Tuesday, September 2, 2025)]
[Notices]
[Pages 42451-42453]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-16769]
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NUCLEAR REGULATORY COMMISSION
[NRC-2025-0775]
Level 3 Probabilistic Risk Assessment Project Documentation
(Volume 5)
AGENCY: Nuclear Regulatory Commission.
ACTION: Draft report; request for comment.
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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing for
public comment a draft report on the Level 3 Probabilistic Risk
Assessment (PRA) project; specifically, ``Volume 5: Overview of
Reactor, Low-Power and Shutdown, Level 1, 2, and 3 PRAs for Internal
Events.''
DATES: Submit comments by November 3, 2025. Comments received after
this date will be considered if it is practical to do so, but the
Commission is able to ensure consideration only for comments received
on or before this date.
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ADDRESSES: You may submit comments by any of the following methods;
however, the NRC encourages electronic comment submission through the
Federal rulemaking website:
Federal rulemaking website: Go to https://www.regulations.gov and search for Docket ID NRC-2025-0775. Address
questions about Docket IDs in Regulations.gov to Bridget Curran;
telephone: 301-415-1003; email: [email protected]. For technical
questions, contact the individual(s) listed in the For Further
Information Contact section of this document.
Mail comments to: Office of Administration, Mail Stop:
TWFN-7-A60M, U.S. Nuclear Regulatory Commission, Washington, DC 20555-
0001, ATTN: Program Management, Announcements and Editing Staff.
For additional direction on obtaining information and submitting
comments, see ``Obtaining Information and Submitting Comments'' in the
SUPPLEMENTARY INFORMATION section of this document.
FOR FURTHER INFORMATION CONTACT: Alan Kuritzky, Office of Nuclear
Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001; telephone: 301-415-1552; email: [email protected].
SUPPLEMENTARY INFORMATION:
I. Obtaining Information and Submitting Comments
A. Obtaining Information
Please refer to Docket ID NRC-2025-0775 when contacting the NRC
about the availability of information for this action. You may obtain
publicly available information related to this action by any of the
following methods:
Federal Rulemaking Website: Go to https://www.regulations.gov and search for Docket ID NRC-2025-0775.
NRC's Agencywide Documents Access and Management System
(ADAMS): You may obtain publicly available documents online in the
ADAMS Public Documents collection at https://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``Begin Web-based ADAMS
Search.'' For problems with ADAMS, please contact the NRC's Public
Document Room (PDR) reference staff at 1-800-397-4209, at 301-415-4737,
or by email to [email protected]. For the convenience of the reader,
instructions about obtaining materials referenced in this document are
provided in the ``Availability of Documents'' section.
NRC's PDR: The PDR, where you may examine and order copies
of publicly available documents, is open by appointment. To make an
appointment to visit the PDR, please send an email to
[email protected] or call 1-800-397-4209 or 301-415-4737, between 8
a.m. and 4 p.m. eastern time (ET), Monday through Friday, except
Federal holidays.
B. Submitting Comments
The NRC encourages electronic comment submission through the
Federal rulemaking website (https://www.regulations.gov). Please
include Docket ID NRC-2025-0775 in your comment submission.
The NRC cautions you not to include identifying or contact
information that you do not want to be publicly disclosed in your
comment submission. The NRC will post all comment submissions at
https://www.regulations.gov as well as enter the comment submissions
into ADAMS. The NRC does not routinely edit comment submissions to
remove identifying or contact information.
If you are requesting or aggregating comments from other persons
for submission to the NRC, then you should inform those persons not to
include identifying or contact information that they do not want to be
publicly disclosed in their comment submission. Your request should
state that the NRC does not routinely edit comment submissions to
remove such information before making the comment submissions available
to the public or entering the comment into ADAMS.
II. Discussion
As directed in SRM-SECY-11-0089, ``Options for Proceeding with
Future Level 3 Probabilistic Risk Assessment (PRA) Activities,'' the
staff is conducting a full-scope multi-unit site Level 3 PRA (Level 3
PRA project) that addresses all internal and external hazards; all
plant operating modes; and all reactor units, spent fuel pools, and dry
cask storage. For definitional purposes, a Level 1 PRA estimates the
frequency of accidents that cause damage to the nuclear reactor core;
this is commonly called core damage frequency. A Level 2 PRA starts
with the Level 1 core damage accidents and estimates the frequency of
accidents that release radioactivity from the nuclear power plant. A
Level 3 PRA starts with the Level 2 radioactivity release accidents and
estimates the consequences in terms of injury to the public and damage
to the environment.
The reference site for this study contains 2 four-loop Westinghouse
pressurized water reactors with large dry containments. The objectives
of the Level 3 PRA project are to (1) develop a Level 3 PRA, generally
based on current state-of-practice methods, tools, and data, that (a)
reflects technical advances since the last NRC-sponsored Level 3 PRAs
(NUREG-1150), which were completed over 30 years ago, and (b) addresses
scope considerations that were not previously considered (e.g., low-
power and shutdown risk, multi-unit risk, other radiological sources);
(2) extract new insights to enhance regulatory decision making and to
help focus limited NRC resources on issues most directly related to the
agency's mission to protect public health and safety; (3) enhance PRA
staff capability and expertise and improve documentation practices to
make PRA information more accessible, retrievable, and understandable;
and (4) demonstrate technical feasibility and evaluate the realistic
cost of developing new Level 3 PRAs.
The work performed under this project is being documented as a
multi-volume report. The current Level 3 PRA project reports (Volume 5)
describe the analyses and results for the reactor, low-power and
shutdown, Level 1, 2, and 3 PRAs for internal events. Each set of Level
3 PRA project reports covering the Level 1, 2, and 3 PRAs for a
specific site radiological source, plant operating state, and hazard
group (or groups) is accompanied by an overview report. The overview
reports summarize the results and insights from all three PRA levels.
The Level 3 PRA project analyses reflect the reference plant as it
was designed and operated as of 2012. To provide results and insights
better aligned with the current design and operation of the reference
plant, the overview reports also provide a reevaluation of the plant
risk based on a set of new plant equipment and PRA model assumptions
and compare the results of the reevaluation to the original study
results. This reevaluation reflects the potential impact of FLEX
strategies (which reduce the risk to the public), as well as the
current reactor coolant pump shutdown seal design (which has limited
risk impact during low-power and shutdown conditions).
As documented in Section 2 of the Volume 5 overview report, the
results of the original Level 3 PRA project analyses and the
reevaluation both show that the combination of this plant design and
site location has substantial margin to the quantitative health
objectives related to the NRC's safety goal policy when considering
internal events during reactor shutdown, though the margins are
noticeably less for the surrogate risk metrics of core damage frequency
and large, early release frequency. Even though these margins can vary
for other
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plants due to variations in their design and siting, the estimates
derived for the reference plant, when adjusted for siting and design
variations, would provide useful qualitative risk insights for other
U.S. operating plants.
III. Availability of Documents
The documents identified in the following table are available to
interested persons through ADAMS, as indicated.
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Adams accession
Document description No.
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SRM-SECY-11-0089, ``Options for Proceeding with ML112640419
Future Level 3 Probabilistic Risk Assessment (PRA)
Activities,'' dated September 21, 2011..............
Level 3 PRA Project, Volume 5: Overview of Reactor, ML25157A084
Low-Power and Shutdown, Level 1, 2, and 3 PRAs for
Internal Events (draft for public comment),
published September 2025............................
Level 3 PRA Project, Volume 5a: Reactor, At-Shutdown, ML25157A085
Level 1 PRA for Internal Events, published September
2025................................................
Level 3 PRA Project, Volume 5b: Reactor, At-Shutdown, ML25157A086
Level 2 PRA for Internal Events, published September
2025................................................
Level 3 PRA Project, Volume 5c: Reactor, At-Shutdown, ML25157A087
Level 3 PRA for Internal Events, published September
2025................................................
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Dated: August 28, 2025.
For the Nuclear Regulatory Commission.
Latonia Enos-Sylla,
Acting Chief, Probability Risk Assessment Branch, Division of Risk
Analysis, Office of Nuclear Regulatory Research.
[FR Doc. 2025-16769 Filed 8-29-25; 8:45 am]
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