[Federal Register Volume 83, Number 21 (Wednesday, January 31, 2018)]
[Notices]
[Pages 4520-4521]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-01901]


=======================================================================
-----------------------------------------------------------------------

NUCLEAR REGULATORY COMMISSION

[NRC-2012-0110]


An Approach for Using Probabilistic Risk Assessment in Risk-
Informed Decisions on Plant-Specific Changes to the Licensing Basis

AGENCY: Nuclear Regulatory Commission.

ACTION: Regulatory guide; issuance.

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

SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing 
Revision 3 to Regulatory Guide (RG) 1.174, ``An Approach for Using 
Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-
Specific Changes to the Licensing Basis.'' This proposed guide, 
Revision 3, has been revised to incorporate additional information 
related to the evaluation of defense-in-depth since Revision 2 of RG 
1.174 was issued in 2011. The proposed revision includes additional 
guidance on defense-in-depth to assure the defense-in-depth philosophy 
is interpreted and implemented consistently.

DATES: Revision 3 to RG 1.174 is available on January 31, 2018.

ADDRESSES: Please refer to Docket ID NRC-2012-0110 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 http://www.regulations.gov and search for Docket ID NRC-2012-0110. Address 
questions about NRC dockets to Carol Gallagher; telephone: 301-415-
3463; 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 
(ADAMS): You may obtain publicly-available documents online in the 
ADAMS Public Documents collection at http://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``ADAMS Public Documents'' and 
then 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. Revision 3 to RG 1.174 and the regulatory analysis may be 
found in ADAMS under Accession Nos. ML17317A256 and ML16358A156 
respectively.
     NRC's PDR: You may examine and purchase copies of public 
documents at the NRC's PDR, Room O1-F21, One White Flint North, 11555 
Rockville Pike, Rockville, Maryland 20852.
    Regulatory guides are not copyrighted, and NRC approval is not 
required to reproduce them.

FOR FURTHER INFORMATION CONTACT: Anders Gilbertson, telephone: 301-415-
1541, email: [email protected], and Harriet Karagiannis, 
telephone: 301-415-2493, email: [email protected]. Both are 
staff of the Office of Nuclear Regulatory Research, U.S. Nuclear 
Regulatory Commission, Washington, DC 20555-0001.

SUPPLEMENTARY INFORMATION:

I. Discussion

    The NRC is issuing a revision to an existing guide in the NRC's 
``Regulatory Guide'' series. This series was developed to describe and 
make available to the public information regarding methods that are 
acceptable to the NRC staff for implementing specific parts of the 
agency's regulations, techniques that the NRC staff uses in evaluating 
specific issues or postulated events, and data that the NRC staff needs 
in its review of applications for permits and licenses. Revision 3 of 
RG 1.174 describes an approach that is acceptable to the staff of the 
NRC when developing risk-informed applications for a licensing basis 
change that considers engineering issues and applies risk insights.
    Revision 3 of RG 1.174 was issued with a temporary identification 
of Draft Regulatory Guide, DG-1285. This revision (Revision 3) presents 
up-to-date defense-in-depth guidance using precise language to assure 
the defense-in-depth philosophy is interpreted and implemented 
consistently. Revision 3 contains significant changes including 
expansion of the guidance on the meaning of, and the process for 
assessing, the defense-in-depth considerations.
    In addition, this revision adopts the term ``PRA Acceptability,'' 
including related phrasing variants, in place of terms such as ``PRA 
quality,'' ``PRA technical adequacy,'' and ``technical

[[Page 4521]]

adequacy'' to describe the appropriateness of the PRA used to support 
risk-informed licensing submittals. Other changes in this revision 
include expanding the discussions on uncertainties, including 
aggregation of risk results, consistent with NUREG-1855, ``Guidance on 
the Treatment of Uncertainties Associated with PRAs in Risk-Informed 
Decisionmaking'' (ADAMS Accession No. ML17062A466), updating the risk 
acceptance guideline figures, and incorporating discussions related to 
application of this guide to new reactors.
    Regarding the guidance in Section C.6.3 of the guide on the 
licensee submittal documentation, the NRC has accepted via a letter 
issued on May 3, 2017 (See ADAMS Accession No. ML17079A427), an 
industry process entitled ``Close-out of Facts and Observations 
(F&Os)'' (See ADAMS Accession No. ML17086A431) that allows a licensee 
to formally close F&Os that were generated during a peer review 
process. If a licensee meets the conditions of acceptance as described 
in the NRC's letter, a licensee does not need to submit the closed F&Os 
in any future applications. It should be noted that the NRC position in 
the May 3rd letter is expected to be incorporated into the next 
revision of RG 1.200, ``An Approach for Determining the Technical 
Adequacy of Probabilistic Risk Assessment Results for Risk-Informed 
Activities.''

II. Additional Information

    The NRC published a notice of the availability of DG-1285 in the 
Federal Register on April 7, 2017 (82 FR 17042), for a 45-day public 
comment period. The public comment period closed on May 22, 2017. 
Public comments on DG-1285 and the staff responses to the public 
comments are available under ADAMS under Accession No. ML17261A618.

III. Congressional Review Act

    This RG is a rule as defined in the Congressional Review Act (5 
U.S.C. 801-808). However, the Office of Management and Budget has not 
found it to be a major rule as defined in the Congressional Review Act.

IV. Backfitting and Issue Finality

    RG 1.174 describes an approach that the NRC staff considers 
acceptable when developing risk-informed applications for a licensing 
basis change that considers engineering issues and applies risk 
insights. Issuance of this RG does not constitute backfitting as 
defined in section 50.109 of title 10 of the Code of Federal 
Regulations (10 CFR) (the Backfit Rule) and is not otherwise 
inconsistent with the issue finality provisions in 10 CFR part 52. As 
discussed in the ``Implementation'' section of this RG, the NRC has no 
current intention to impose this guidance on holders of current 
operating licenses or combined licenses.
    This RG may be applied to applications for amendments to operating 
licenses or combined licenses docketed by the NRC as of the date of 
issuance, as well as future applications submitted after the issuance 
of this regulatory guide. Such action would not constitute backfitting 
as defined in the Backfit Rule or be otherwise inconsistent with the 
applicable issue finality provision in 10 CFR part 52, inasmuch as such 
applicants or potential applicants are not within the scope of entities 
protected by the Backfit Rule or the relevant issue finality provisions 
in part 52.

    Dated at Rockville, Maryland, this 25th day of January 2018.

    For the Nuclear Regulatory Commission.
Edward O'Donnell,
Acting Chief, Regulatory Guidance and Generic Issues Branch, Division 
of Engineering, Office of Nuclear Regulatory Research.
[FR Doc. 2018-01901 Filed 1-30-18; 8:45 am]
 BILLING CODE 7590-01-P