[Federal Register Volume 87, Number 199 (Monday, October 17, 2022)]
[Notices]
[Pages 62894-62896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-22536]


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NUCLEAR REGULATORY COMMISSION

[NRC-2022-0052]


Acceptability of Probabilistic Risk Assessment Results for Non-
Light Water Reactor Risk-Informed Activities

AGENCY: Nuclear Regulatory Commission.

ACTION: Regulatory guide for trial use; response to comments.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is addressing 
comments received after issuing for public comment on the trial use of 
the new regulatory guide (RG) 1.247, ``Acceptability of Probabilistic 
Risk Assessment Results for Non-Light Water Reactor Risk-Informed 
Activities.'' The NRC will not make any changes to the RG as a result 
of these comments.

DATES: The public comment period for RG 1.247 ended on May 23, 2022.

ADDRESSES: Please refer to Docket ID NRC-2022-0052 when contacting the 
NRC about the availability of information regarding this document. You 
may obtain publicly available information related to this document 
using any of the following methods:
     Federal Rulemaking Website: Go to https://www.regulations.gov and search for Docket ID NRC-2022-0052. Address 
questions about Docket IDs in Regulations.gov to Stacy Schumann; 
telephone: 301-415-0624; email: [email protected]. For technical 
questions, contact the individuals listed in the FOR FURTHER 
INFORMATION CONTACT section of this document.
     NRC's Agencywide Documents Access and Management System

[[Page 62895]]

(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, 301-415-4737, or 
by email to [email protected]. The ADAMS accession number for each 
document referenced (if it is available in ADAMS) is provided the first 
time that it is mentioned in this document.
     NRC's PDR: You may examine and purchase copies of public 
documents, by appointment, at the NRC's PDR, Room P1 B35, One White 
Flint North, 11555 Rockville Pike, Rockville, Maryland 20852. 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 
8:00 a.m. and 4:00 p.m. Eastern Time (ET), Monday through Friday, 
except Federal holidays.
    RG 1.247 for trial use and the regulatory analysis may be found in 
ADAMS under Accession Nos. ML21235A008 and ML21235A010, respectively.
    Regulatory guides are not copyrighted, and NRC approval is not 
required to reproduce them.

FOR FURTHER INFORMATION CONTACT: Michelle Gonzalez, telephone: 301-415-
5661, email: [email protected], Anders Gilbertson, telephone: 
301-415-1541, email: [email protected], or Harriet Karagiannis, 
telephone: 301-415-2493, email: [email protected]. These 
individuals are staff in the Office of Nuclear Regulatory Research at 
the U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

SUPPLEMENTARY INFORMATION:

I. Background

    The NRC has issued for trial use this new RG titled, 
``Acceptability of Probabilistic Risk Assessment Results for Non-Light 
Water Reactor Risk-Informed Activities,'' and it is designated as trial 
use RG 1.247. It describes one acceptable approach for determining 
whether a design-specific or plant-specific probabilistic risk 
assessment (PRA) used to support an application is sufficient to 
provide confidence in the results, such that the PRA can be used in 
regulatory decision-making for non-light water reactors (NLWRs) for 
implementing the requirements in part 50 and 52 of title 10 of the Code 
of Federal Regulations (10 CFR). In addition, this trial use RG is 
intended to be consistent with the NRC's PRA Policy Statement and 
reflects and endorses, with staff exceptions, national consensus PRA 
standards provided by standards development organizations and guidance 
provided by nuclear industry organizations. As a trial use RG, this 
issuance allows early use prior to general implementation, and the 
guidance may be revised based on experience obtained by the NRC from 
the implementation of the trial use RG.
    The staff is planning to conduct a public meeting by the end of 
calendar year 2022 to obtain stakeholder feedback on the development of 
a draft guide, which will be issued at the conclusion of the trial use 
period, and subsequent final publication of RG 1.247. The NRC will also 
provide an additional opportunity for formal public comment on the 
planned draft RG, with feedback considered prior to final RG 
publication.

II. Public Comments

    This trial use RG was not published for public comment as a draft 
RG. Trial use RG 1.247 was issued for a 60-day, post-promulgation 
public comment in the Federal Register on March 24, 2022 (87 FR 16770). 
Pursuant to 10 CFR 2.804(e), the NRC must publish in the Federal 
Register an evaluation of any significant comments and describe any 
revisions made as a result of the comments and their evaluation.
    The public comment period ended on May 23, 2022, and comments were 
received from two organizations (Nuclear Energy Institute (NEI) and X-
energy). NEI and X-energy submitted separate comments on the staff 
endorsement of items HLR-HR-E and HR-E4 from the American Society of 
Mechanical Engineers (ASME) and American Nuclear Society (ANS) NLWR PRA 
standard. The staff considers these comments significant to the extent 
they warrant a response to clarify the record. While the staff is not 
responding in this notice to the other comments submitted in response 
to the opportunity to comment the NRC published at 87 FR 16770, the 
staff will consider those comments in preparing a draft of RG 1.247 for 
comment or in considering the experience obtained through trial use of 
RG 1.247.
    For items HLR-HR-E and HR-E4, the staff takes exceptions to the 
ASME and ANS NLWR PRA standard regarding the treatment of errors of 
commission (EOCs) in a PRA. The exceptions provide for consideration of 
EOCs that result in adverse safety impacts for Compatibility Category 
I, (CC-I). CC-I defines the minimum capability needed for a PRA 
element. In contrast, Compatibility Category II (CC-II) defines the 
minimum capability needed to meet current good practice standards for 
each PRA element. The comments indicate that these exceptions are not 
consistent with the current PRA state of practice, which does not call 
for broad consideration of EOCs for PRAs for LWRs as per the NRC 
endorsement of HR-E4 in the trial use RG. Thus, the comment contends 
that broadly considering EOCs goes above and beyond the requirement for 
the current operating fleet. Although no changes were made to the trial 
use RG based on these comments, the staff provides a brief discussion 
on these significant comments.
    Specifically, the comment recommends that this exception to HR-E4 
and the HLR-HR-E be removed from the trial use RG or only be applicable 
for CC-II of HR-E4, the latter of which would represent good practice 
as opposed to a minimum capability. Another comment notes that the 
trial use RG 1.247 includes additional language on the scope of such 
considerations; however, the comment states that this added language 
does not maintain consistency with the LWR PRA standard. The comment 
supports retaining consistency with the LWR PRA standard in the trial 
use RG 1.247, which would call for removal of this added exception 
regarding consideration of EOCs in the NLWR PRA standard.
    The staff is keeping the exceptions related to EOCs in this trial 
use RG, which is based on the following consideration. The development 
efforts for the ASME/ANS NLWR PRA standard relied substantially on the 
development efforts for the next edition of the ASME/ANS Level 1/large 
early release frequency (LERF) LWR PRA standard and, in many cases, the 
NLWR PRA standard adopted the same or similar requirements as the next 
edition of the Level 1/LERF LWR PRA standard. However, the Level 1/LERF 
LWR PRA standard state of practice relies on significant LWR operating 
experience that facilitates a consensus to generally exclude EOCs from 
LWR PRAs, but no similar body of operating experience underlies the 
NLWR PRA standard.
    Because there is limited operating experience regarding EOCs for 
NLWRs and the scope of the ASME/ANS NLWR PRA standard is broader than 
the scope of the ASME/ANS Level 1/LERF LWR PRA standard, EOCs may play 
a more important role in NLWR PRA than for LWR PRA and, therefore, NLWR 
PRA developers will need to demonstrate that EOCs are not an issue 
before

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eliminating them from consideration. However, the staff also notes that 
such identification of EOCs is generally expected to apply to a PRA 
developed for the operational phase of a plant's lifecycle. This is 
based on the premise that there is expected to be a general lack of 
available, relevant information that would allow meaningful 
identification of EOCs in pre-operational stages of a plant's 
lifecycle. Related staff guidance on the treatment of such EOCs during 
pre-operational phases of a plant's lifecycle is currently under 
development.
    A comment states that EOCs are already captured in FHR-A1 at CC-II 
for fires where operating experience supports consideration of spurious 
signals. Therefore, the comment notes that the RG 1.247 position on HR-
E4 requiring EOCs at CC-I is not internally consistent with the trial 
use RG position on FHR-A1 requiring EOCs only at CC-II. The comment 
also states that, for non-fire hazards, spurious signals should occur 
with low frequency and would require significant operator error due to 
the redundancy of information available to the operator.
    The staff notes that, while the consideration of spurious signals 
as a potential cause of an EOC is important and spurious signals may 
occur due to fire damage, such spurious signals are not the only reason 
an EOC may occur. NUREG-1880, ``ATHEANA User's Guide,'' (ADAMS 
Accession No. ML072130359) recommends searching for potential EOCs and 
the contexts that could cause them. However, while the staff maintains 
that other sources of EOCs should be considered for identification in 
CC-I of FHR-A1, the staff did not intend for new, undesired operator 
actions that could result from spurious indications from fire-induced 
failure of a single instrument to be identified to meet CC-I of FHR-A1. 
The staff would therefore not call for such identification as part of 
meeting the trial use RG. The staff notes that while the comment 
characterizes the staff positions as ``requirements,'' no regulatory 
guide establishes requirements. Rather, the exceptions and 
clarifications in a regulatory guide are guidance to an applicant 
stating elements of an acceptable method for complying with NRC 
regulations.

    Dated: October 12, 2022.

    For the Nuclear Regulatory Commission.
Meraj Rahimi,
Chief, Regulatory Guide and Programs Management Branch, Division of 
Engineering, Office of Nuclear Regulatory Research.
[FR Doc. 2022-22536 Filed 10-14-22; 8:45 am]
BILLING CODE 7590-01-P