ML16285A421
| ML16285A421 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 10/20/2016 |
| From: | Frankie Vega Japan Lessons-Learned Division |
| To: | Pierce C Southern Nuclear Company |
| Vega F, NRR/JLD 301-415-1617 | |
| References | |
| CAC MF3772, CAC MF3773 | |
| Download: ML16285A421 (4) | |
Text
UNITED ST ATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. C. R. Pierce Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
P.O. Box 1295 /BIN B038 Birmingham, AL 35201-1295 October 20, 2016
SUBJECT:
EDWIN I. HATCH NUCLEAR PLANT, UNITS 1 AND 2 - STAFF REVIEW OF LOW FREQUENCY LIMITED-SCOPE EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1 (CAC NOS. MF3772 AND MF3773}
Dear Mr. Pierce:
The purpose of this letter is to inform Southern Nuclear Operating Co., Inc. (the licensee) of the results of the U.S. Nuclear Regulatory Commission (NRC) staff's review of the low frequency (LF) limited scope evaluation for Edwin I. Hatch Nuclear Plant, Units 1 and 2 (HNP, Hatch),
which was submitted in response to NRC's March 12, 2012, request for information (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340), issued under Title 1 O of the Code of Federal Regulations Part 50, Section 50.54(f) (hereafter referred to as the 50.54(f) letter). Electric Power Research Institute (EPRI)
Report 1025287, "Seismic Evaluation Guidance: Screening, Prioritization and Implementation Details (SPID)" (ADAMS Accession No. ML12333A170) provides guidance for licensees to evaluate LF exceedances. The NRC staff concludes that the licensee's assessment was performed consistent with the NRG-endorsed SPID Guidance and that the licensee has provided sufficient information to complete the response to Item 4 of the 50.54(f) request for information.
BACKGROUND By letter dated March 12, 2012, the NRC issued a request for information. The request was issued as part of implementing lessons learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 1 to the 50.54(f) letter requested that licensees reevaluate seismic hazards at their sites using present-day methodologies and guidance. Enclosure 1, Item 4, of the 50.54(f) letter requested that licensees perform a comparison of the ground motion response spectrum (GMRS) and safe shutdown earthquake (SSE); if the GMRS exceeds the SSE at higher frequencies, information related to the functionality of high-frequency sensitive structures, systems, and components (SSCs) is requested. This request also applies to cases in which the GMRS exceeds the SSE in the LF range (i.e., below 2.5 Hertz (Hz)). The licensee's HF evaluation is expected by August 31, 2017. The staff's assessment of the information provided in response to Items 1-3 and 5-7 of the 50.54(f) is provided by letter dated April 27, 2015 (ADAMS Accession No. ML15097A424).
By letter dated October 27, 2015 (ADAMS Accession No. ML15194A015), the NRG staff stated that a limited-scope LF evaluation for HNP was expected by December 31, 2016. The licensee's HF evaluation is expected by August 31, 2017 REVIEW OF LICENSEE LIMITED-SCOPE LOW FREQUENCY EVALUATION By letter dated August 10, 2016 (ADAMS Accession No. ML16223A544), SNP submitted its limited-scope LF evaluation for Hatch for NRG review.
TECHNICAL EVALUATION Section 3.2.1.1 of the SPID provides guidance to licensees when performing evaluations for LF exceedances at low seismic hazard sites. This section states that for these sites, licensees should identify and evaluate the seismic capacity of all safety-significant SSCs that are potentially susceptible to damage from spectral accelerations at frequencies below 2.5 Hz.
Section 3.2.1.1 of the SPID provides examples of SSCs and failure modes that are considered to be potentially susceptible to damage from spectral accelerations at LF and provides criteria to evaluate the capacity of such SSCs. The staff's review consists of reviewing the licensee's approach to ensure that potentially LF susceptible SSCs are properly identified and evaluated as described in the SPID.
1.1 HNP Limited-Scope LF Evaluation The licensee followed the guidance in SPID Section 3.2.1.1 when performing LF evaluations for HNP. The licensee stated that it used available information from previous and ongoing seismic evaluations to assess the seismic capacities of SSCs that were considered to be potentially susceptible to LF considerations and identify any potential safety significant vulnerabilities due to the LF exceedances. The licensee performed seismic capacity vs. demand comparisons of those SSCs listed in the SPID and for other SSCs that were identified as potentially susceptible to LF based on previous or ongoing seismic evaluations. The licensee concluded that no LF vulnerabilities exsist and that those potentially LF vulnerable SSCs were found to have seismic capacities greater than the GMRS.
1.2 NRG Staff Technical Assessment The NRG staff reviewed HNP's evaluation used to address SSCs that could be susceptible to damage from spectral accelerations at LFs. The NRG staff reviewed the applicability of the licensee's approach in using previous and ongoing seismic evaluations to perform their assessment. The staff notes that these evaluations, which used ground motions greater that the GMRS, were appropriately used to identify and evaluate the respective seismic capacities of those SSCs. The staff also notes that the licensee's approach followed the guidance in the SPID.
CONCLUSION The NRG staff reviewed SNP's limited-scope low frequency evaluation. Based on its review, the NRG staff concludes that the licensee acceptably evaluated those SSCs that could be susceptible to damage from spectral accelerations at LFs.
In addition, the NRC staff concludes that the licensee's implementation of the LF evaluation met the SPID Guidance for HNP and therefore, the licensee responded appropriately to Item 4 in of the NRC's 50.54(f) letter.
If you have any questions, please contact me at (301) 415-1617 or via e-mail at Frankie.Vega@nrc.gov.
Docket Nos. 50-321 and 50-366 cc: Distribution via Listserv Sincerely, Frankie Vega, ~anager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
- via e-mail OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRR/JLD/JHMB/BC NAME FVega SLent GBowman DATE 10/19/2016 10/18/2016 10/20/2016 OFFICE NRR/JLD/JHMB/PM NAME FVega DATE 10/20/2016