[Federal Register Volume 86, Number 174 (Monday, September 13, 2021)]
[Notices]
[Pages 50913-50914]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-19636]
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NUCLEAR REGULATORY COMMISSION
[NRC-2020-0237]
Considerations for Estimating Site-Specific Probable Maximum
Precipitation at Nuclear Power Plants in the United States of America
AGENCY: Nuclear Regulatory Commission.
ACTION: NUREG; issuance.
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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing a
knowledge management NUREG, NUREG/KM-0015, ``Considerations for
Estimating Site-Specific Probable Maximum Precipitation at Nuclear
Power Plants in the United States of America.'' The NRC staff and Oak
Ridge National Laboratory have prepared a reference document
summarizing recent lessons-learned in connection with a review of the
site-specific probable maximum precipitation (SSPMP) estimates used by
some nuclear power plant owners and operators in connection with a
recent re-evaluation of external flooding at their respective project
sites.
DATES: NUREG/KM-0015 is available on September 13, 2021.
ADDRESSES: Please refer to Docket ID NRC-2020-0237 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-2020-0237. Address
questions about Docket IDs in Regulations.gov to Stacy Schumann;
telephone: 301-415-0624; email: [email protected]. For technical
questions, contact the individual 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 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]. NUREG/KM-0015, ``Considerations for
Estimating Site-Specific Probable Maximum Precipitation at Nuclear
Power Plants in the United States of America'' is available in ADAMS
under Accession No. ML21245A418.
Attention: The PDR, where you may examine, and order
copies of public documents, is currently closed. You may submit your
request to the PDR via email at [email protected] or call 1-800-397-
4209 or 301-415-4737, between 8:00 a.m. and 4:00 p.m. (ET), Monday
through Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT: Kevin Quinlan, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001; telephone: 301-415-6809, email: [email protected].
SUPPLEMENTARY INFORMATION:
I. Background
By letter dated March 12, 2012, the NRC issued a request for
information to all power reactor licensees and holders of construction
permits in active or deferred status licensees to reevaluate seismic
and external flooding for their sites against current Commission
requirements and guidance. This request was made consistent with
paragraph 50.54(f) of title of the Code of Federal Regulations (10
CFR), ``Conditions of licenses.'' The request was issued in connection
with implementing lessons-learned identified by the staff, and
described in their Near-Term Task Force Report, following the 2011
accident at the Fukushima Dai-ichi nuclear power plant. In connection
with this request, owners and operators were to re-evaluate flood
hazards at their respective sites using present-day methods and
regulatory guidance used by the NRC staff when reviewing 10 CFR part 52
applications for Early Site Permits and Combined Operating Licenses.
In response to the staff's 2012 Sec. 50.54(f) information request,
owners and licensees submitted about 60 external flood hazard re-
evaluation reports (FHRRs) corresponding to the operating fleet of
power reactors. In the matter of the probable maximum precipitation
(PMP) value used for some of the flood-hazard re-evaluations (primarily
the estimation of local intense precipitation and riverine-based
floods), current NRC guidance documents recommend the use of the PMP
estimation methods described in a series of Hydrometeorological Reports
(HMRs) developed by the National Oceanographic and Atmospheric
Administration (NOAA). The PMP event itself is generally defined as the
greatest depth of precipitation for a given duration meteorologically
possible for a design watershed or a given storm area at a particular
time of year. The estimated PMP over a particular watershed or basin
results in a flood magnitude for which there is virtually no risk of
exceeding. The challenge, however, is that HMR-derived PMP estimates
are based on methodologies and data which have not been updated with
rainfall and storm events which have occurred in the decades since the
HMRs were last published.
Upon review of the FHRRs, the staff found that about 26 project
sites responding to the Sec. 50.54(f) information request submitted
PMP estimates that were not based on NOAA HMRs but were developed by a
commercial interest. As part of the FHRR process, the staff conducted
an audit of the commercial vendor who developed the site-specific PMP
estimates to better-understand the technical basis underlying the
approach. In all cases, these SSPMP estimates were less than those
obtained from the applicable HMR. Although the development and
estimation of the SSPMP studies reviewed by the staff generally
followed processes similar to those described in the existing guidance,
several different methods, data sources, assumptions, and procedures
were used to obtain site specific results other than those found using
the HMR methodology.
Based on the staff's Sec. 50.54(f) review experience and in
anticipation of its continued use, this NUREG summarizes the lessons-
learned concerning the review and application of a SSPMP. To that end,
this NUREG addresses the following topics:
Storm Selection
Storm Reconstruction
Storm Transposition
[[Page 50914]]
Storm Representative Dew Point Selection
Precipitable Water Estimation
Dew Point Climatology, Moisture Maximization, and Moisture
Transposition
Terrain Adjustment
Envelopment and Probable Maximum Precipitation Determination
Spatial and Temporal Distributions for SSPMP Applications
This reference document describes the technical theory, data
sources, and analysis methodology that could be used to derive a SSPMP
estimate. Certain new terms are also introduced and defined. This
reference document also identifies key technical (meteorological)
considerations when reviewing a SSPMP estimate.
To date, there is no clear NRC guidance on this topic or a commonly
agreed-to approach on the estimation of SSPMP. As the staff may be
reviewing additional SSPMP estimates in the future in connection with
its regulatory responsibilities, it was decided to elicit stakeholder
views on the matters and approaches discussed in this draft document.
This document contains no regulatory guidance or regulatory
positions.
A request for comments on draft NUREG/KM-0015, (ADAMS Accession No.
ML20356A293) was published in the Federal Register on December 29, 2020
(85 FR 85683), with a 60-day comment period ending on March 1, 2021.
Comments received on NUREG/KM-0015 can be found on the Federal
Rulemaking website (https://www.regulations.gov) under Docket ID NRC-
2020-0237.
II. Knowledge Management
Since its inception, the Atomic Energy Commission and its
successor, the NRC, have focused on preserving the (explicit)
documentary record of its decision-making in the form of NUREGs, SECY
Papers, Regulatory Guides, and other documents. However, in 2006, the
agency recognized that there was a need to engage in a more-formal
program of knowledge management that also reflects the less-tangible
(implicit) human capital aspect of the agencies' knowledge base. This
feature was particularly important as the agency enters its fifth
decade of operation--a period characterized by an increasing number of
retirements among long-serving staff involved in many of the agencies'
early regulatory programs and associated licensing actions. Staff
efforts thus far in preserving this legacy of experience that describe
important historical events, facts, and research that were instrumental
in shaping NRC's regulatory programs, can be found at https://www.nrc.gov/reading-rm/doc-collections/nuregs/knowledge/.
The purpose of this knowledge management NUREG (or NUREG/KM) is
intended to satisfy an NRC goal of maintaining and preserving knowledge
concerning the lessons-learned from the recent flood hazard re-
evaluations at current and planned nuclear power plant sites performed
most recently in connection with the staff 2012 Sec. 50.54(f) reviews.
Dated: September 8, 2021.
For the Nuclear Regulatory Commission.
Luissette Candelario-Quintana,
Project Manager, External Hazards Branch, Division of Engineering and
External Hazards, Office of Nuclear Reactor Regulation.
[FR Doc. 2021-19636 Filed 9-10-21; 8:45 am]
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