[Federal Register Volume 84, Number 126 (Monday, July 1, 2019)]
[Notices]
[Pages 31354-31355]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-13928]


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NUCLEAR REGULATORY COMMISSION

[NRC-2019-0119]


Methodology for Modeling Fire Growth and Suppression for 
Electrical Cabinet Fires in Nuclear Power Plants

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 entitled, ``Methodology for Modeling Fire 
Growth and Suppression for Electrical Cabinet Fires in Nuclear Power 
Plants'' (NUREG-2230/EPRI 3002016051). This report is a joint product 
of the NRC and the Electric Power Research Institute (EPRI) 
collaborating under a memorandum of understanding for fire research. 
The purpose of this report is to provide an approach that more closely 
models the types of fire progressions and response activities observed 
in operating experience. This report provides a revised set of 
parameters addressing both the fire growth portion and the suppression 
response for electrical cabinet fires.

DATES: Submit comments by July 31, 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: You may submit comments by any of the following methods:
     Federal Rulemaking Website: Go to https://www.regulations.gov/ and search

[[Page 31355]]

for Docket ID NRC-2019-0119. Address questions about docket IDs in 
Regulations.gov to Jennifer Borges; telephone: 301-287-9127; email: 
[email protected]. For technical questions, contact the 
individuals 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: David W. Stroup, Office of Nuclear 
Regulatory Research, telephone: 301-415-1649, email: 
[email protected]; or Nicholas Melly, Office of Nuclear Regulatory 
Research, telephone: 301-415-2392, email: [email protected]. Both 
are staff of the U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001.

SUPPLEMENTARY INFORMATION:

I. Obtaining Information and Submitting Comments

A. Obtaining Information

    Please refer to Docket ID NRC-2019-0119 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-2019-0119.
     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, 301-415-4737, or 
by email to [email protected]. The draft NUREG on ``Methodology for 
Modeling Fire Growth and Suppression Response of Electrical Cabinet 
Fires in Nuclear Power Plants'' is available in ADAMS under Accession 
No. ML19163A293.
     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-2019-0119 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

    Over the past decade, modern fire probabilistic risk assessments 
(PRAs) have been developed using NUREG/CR-6850 (EPRI 1011989), EPRI/NRC 
Fire PRA Methodology for Nuclear Power Facilities. The results show 
that fire can be a significant portion of the overall site risk 
profile, however, the methodology was never fully piloted tested before 
implementation. As a result, some areas of the fire PRAs have been 
found to be overly conservative resulting in potentially unrealistic 
results. Additional research is being conducted to improve the tools, 
methods, and data used for fire PRAs and refine the estimates of risk 
and close technical gaps in the methodology.
    Recent research efforts focused on obtaining more detailed 
information regarding the fire incidents at nuclear power plants. This 
data collection has enabled researchers to obtain more details on the 
fire attributes, timeline, and plant impact. This project specifically 
reviewed the available electrical cabinet fire incident data in an 
effort to update the methodology to better reflect the observed 
operating experience. Insights from the data review served as the basis 
for amending portions of the fire modeling and suppression response to 
more accurately align with operating experience.
    Specifically, the methodology described in this report provides:
     A conceptual fire event tree progression model developed 
through a review of insights from the fire event database. From this 
review, guidance was developed to allow for consistent classification 
of fire events into two different growth profiles, Interruptible and 
Growing.
     Split fractions for Interruptible and Growing fires for 
use in the revised detection-suppression event tree.
     A revised electrical cabinet heat release rate (HRR) 
profile for use in the detailed fire modeling of Interruptible Fires. 
This revised profile includes a pre-growth period of up to 8 minutes of 
negligible HRR. The treatment for the HRR profile for Growing Fires was 
not modified in this research.
     Revisions to the detection-suppression event tree to 
include paths for crediting early intervention by plant personnel as 
well as new parameters to facilitate these revisions. These new 
parameters include an opportunity to credit detection by general plant 
personnel.
     An opportunity for main control room (MCR) indications as 
a means for fire detection when applicable in the detection-suppression 
event tree.
     New suppression curves for electrical cabinets (Bin 15) 
applicable to Interruptible and Growing electrical cabinet fire 
scenarios.
     New suppression curves for the MCR.
     A new electrical fire suppression curve for use with other 
non-cabinet electrical ignition sources (e.g., motors, pumps, 
transformers).
     A probability of automatic smoke detection effectiveness 
for characterizing the ability of spot type smoke detection devices to 
operate in a range of geometric conditions and heat release rates. This 
is necessary for better alignment with operating experience, which 
suggests that the majority of the fires are detected by plant personnel 
and MCR indicators instead of automatic smoke detection systems.
     An updated Bin 15 fire frequency that makes use of the 
fire event data classified in EPRI 3002005302, Fire Events Database 
Update for the Period 2010-2014.

    Dated at Rockville, Maryland, this 25th day of June 2019.

    For the Nuclear Regulatory Commission.
Mark H. Salley,
Branch Chief, Fire and External Hazards Analysis Branch, Division of 
Risk Analysis, Office of Nuclear Regulatory Research.
[FR Doc. 2019-13928 Filed 6-28-19; 8:45 am]
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