[Federal Register Volume 84, Number 57 (Monday, March 25, 2019)]
[Notices]
[Pages 11136-11137]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-05606]



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NUCLEAR REGULATORY COMMISSION

[NRC-2019-0043]


Credibility Assessment Framework for Critical Boiling Transition 
Models

AGENCY: Nuclear Regulatory Commission.

ACTION: Draft NUREG; request for comment.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing for 
public comment a draft NUREG (U.S. Nuclear Regulatory Commission 
technical report designation), knowledge management NUREG (NUREG/KM) -
0013, ``Credibility Assessment Framework for Critical Boiling 
Transition Models.'' This NUREG describes NRC past practice and staff 
experience in determining the credibility of critical heat flux and 
critical power models and, based on that experience, presents an 
assessment framework that combines aspects of goal structuring notation 
and maturity assessment.

DATES: Submit comments by May 24, 2019. 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 before this 
date.

ADDRESSES: Please refer to Docket ID NRC-2019-0043 when contacting the 
NRC about the availability of information regarding this document. You 
may submit comments by any of the following methods:
     Federal Rulemaking Website: Go to http://www.regulations.gov and search for Docket ID NRC-2019-0043. Address 
questions about NRC dockets IDs in Regulations.gov to Jennifer Borges; 
telephone: 301-287-9127; email: [email protected]. For technical 
questions, contact the individual 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: Joshua Kaizer, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001; telephone: 301-415-1532, email: [email protected].

SUPPLEMENTARY INFORMATION:

I. Obtaining Information and Submitting Comments

A. Obtaining Information

    Please refer to Docket ID NRC-2019-0043 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 http://www.regulations.gov and search for Docket ID NRC-2019-0043.
     NRC's Agencywide Documents Access and Management System 
(ADAMS): You may obtain publicly available documents online in the 
ADAMS Public Document collection at https://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``Begin Web-based ADAMS 
Search.'' For problems with ADAMS, 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. Draft NUREG/KM-0013 is available 
in ADAMS under Accession No. ML19073A249.
     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.

B. Submitting Comments

    Please include Docket ID NRC-2019-0043 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 http://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

    Critical boiling transition (CBT) occurs when a flow regime that 
has a higher heat transfer rate transitions to a flow regime that has a 
significantly lower heat transfer rate. Models that predict a CBT are a 
necessary part of reactor safety analysis because they are used to 
determine plant safety limits. Therefore, the review of CBT models has 
been a focus of the NRC since its inception in 1975.
    Draft NUREG/KM-0013 describes NRC practice and staff experience in 
evaluating CBT models and organizes that practice and staff experience 
in the form of a credibility assessment framework that combines aspects 
of goal structure notation and maturity assessment. The NRC has 
performed many such assessments in the past and has generated this 
framework based on the experience of the current NRC staff and previous 
reviews performed by the staff as summarized in its evaluations. This 
document includes a survey of the important technical and regulatory 
literature; a detailed technical discussion of CBT models and their 
application; and a framework for CBT models that reflects NRC practice 
as a whole, including the level of evidence previously accepted to 
address the various issues relevant to the evaluation of CBT models. 
Accordingly, the NRC is requesting comments on the NUREG-0013/KM 
description of the NRC practice and experience in evaluating CBT models 
and the adequacy of the assessment framework presented.
    The framework presented in NUREG-0013/KM is intended as a 
``textbook'' reference for those interested in the assessment of the 
credibility of CBT models, particularly as applied to reactor safety 
analysis. Nonetheless, Draft NUREG-0013/KM is not guidance to the NRC 
staff, applicants for NRC licenses, or current NRC licensees, and, if 
finalized, would not constitute backfitting, as defined in title 10 of 
the Code of Federal Regulations (10 CFR) 50.109 (the Backfit Rule), or 
otherwise be inconsistent with the issue finality provisions in 10 CFR 
part 52. In the future, the NRC staff may decide to reference NUREG-
0013/KM in guidance to the NRC staff or guidance to applicants or 
licensees, i.e., through an update to the Standard Review Plan or new 
Interim Staff Guidance, or update to a Regulatory Guide, respectively. 
Should the NRC staff decide to do so, the NRC staff will seek public 
comment on the use of NUREG-0013/KM as guidance and will assess any 10 
CFR 50.109 backfitting and part 52 issue

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finality considerations arising from such use.

    Dated at Rockville, Maryland, this 20th day of March 2019.

    For the Nuclear Regulatory Commission.
Robert G. Lukes,
Chief, Nuclear Performance and Code Review, Division of Safety Systems, 
Office of Nuclear Reactor Regulation.
[FR Doc. 2019-05606 Filed 3-22-19; 8:45 am]
 BILLING CODE 7590-01-P