ML15280A022

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood Causing Mechanism Reevaluation (TAC MF5546, MF5547 and MF5548)

ML15280A022
Person / Time
Site:	Palo Verde
Issue date:	10/08/2015
From:	Uribe J F Japan Lessons-Learned Division
To:	Edington R K Arizona Public Service Co
Uribe J, 415-3809, O-13F15M
References
TAC MF5546, TAC MF5547, TAC MF5548
Download: ML15280A022 (3)

Text

October 8, 2015

Mr. Randall K. Edington Executive Vice President Nuclear/CNO Arizona Public Service Company P.O. Box 52034, MS 7602 Phoenix, AZ 85072-2034

SUBJECT:

PALO VERDE NUCLEAR GENERATING STATION, UNITS 1, 2 AND 3 - CORRECTION TO INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION (TAC NOS. MF5546, MF5547 AND MF5548)

Dear Mr. Edington:

By letter dated September 28, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15268A413) the U.S.

Nuclear Regulatory Commission (NRC) transmitted to you the Interim Staff Response to the reevaluated flood hazards for Palo Verde Nuclear Generating Station, Units 1, 2 and 3 (Palo Verde). In that letter, Table 2 is referenced and contains the reevaluated hazards not bounded by current design basis for Palo Verde.

Table 2 was inadvertently omitted from the document and not included in the final version that was transmitted to you. This letter supersedes the September 28, 2015 letter with the only change being the inclusion of Table 2 in the Enclosure to this letter.

The purpose of this letter is to provide a summary of the NRC staff's assessment of the re-evaluated flood-causing mechanisms described in the December 12, 2014 (ADAMS Accession No. ML14350A466), FHRR submitted by APS, for Palo Verde.

By letter dated March 12, 2012, the NRC issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Section 50.54(f) (hereafter referred to as the 50.54(f) letter) (ADAMS Accession No. ML12053A340). The request was issued as part of implementing lessons-learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 2 to the 50.54(f) letter requested licensees to re-evaluate flood-causing mechanisms using present-day methodologies and guidance. Concurrently, with the reevaluation of flooding hazards, licensees were required to develop and implement mitigating strategies in accordance with NRC Order EA-12-049, "Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML12054A735). On March 30, 2015, the Commission provided Staff Requirements Memoranda (SRM) (ADAMS Accession No. ML15089A236) to COMSECY-14-0037, "Integration of Mitigating Strategies for Beyond-Design-Basis External Events and the Reevaluation of Flooding Hazards," dated November 21, 2014 (ADAMS Accession No. ML14309A256), affirming that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyond-design-basis external events.

The NRC staff has reviewed the information submitted by the licensee and has summarized the results of the review in the tables provided as an Enclosure to this letter.

Table 1 provides the current design-basis flood hazard mechanisms. Table 2 provides the reevaluated flood hazard mechanisms; however, the reevaluated flood hazard mechanisms bounded by the current design-basis (Table 1) are not included.

The NRC staff has concluded that the licensee's reevaluated flood hazards information, as summarized in the Enclosure, is suitable for the assessment of mitigating strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in guidance documents currently being finalized by the industry and NRC staff) for

Palo Verde. Further, the NRC staff has concluded that the licensee's reevaluated flood hazard information is a suitable input for other assessments associated with Near-Term Task Force Recommendation 2.1 "Flooding". The NRC staff pl ans to issue a staff assessment documenting the basis for these conclusions at a later time.

In addition, Nuclear Energy Institute (NEI) guidance document NEI 12-06 "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide" is currently being revised. This revision will include a methodology to perform a Mitigating Strategies Assessment (MSA) with respect to the reevaluated flood hazards. Once this methodology is endorsed by the NRC, flood event duration parameters and applicable flood associated effects should be considered as part of the Palo Verde MSA. The NRC staff will evaluate the flood event duration parameters (including warning time and period of inundation) and flood-related associated effects developed by the licensee during the NRC staff's review of the MSA.

As stated above, Table 2 of the enclosure to this letter describes the reevaluated flood hazards that exceed the current design-basis. In order to complete its response to the information requested by Enclosure 2 to the 50.54(f) letter, the licensee is expected to submit an integrated assessment or a focused evaluation, as appropriate, to address these reevaluated flood hazards, as described in the NRC letter, "Coordination of Request for Information Regarding Flooding Hazard Reevaluation and Mitigating Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML15174A257). This letter describes the changes in the NRC's approach to the flood hazard reevaluations that were approved by the Commission in its SRM to COMSECY-15-0019, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants" (ADAMS Accession No. ML15209A682).

If you have any questions, please contact me at (301) 415-3809 or e-mail at Juan.Uribe@nrc.gov@nrc.gov.

Sincerely, /RA/ Juan F. Uribe, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation

Docket Nos. 50-528, 50-529 and 50-530

Enclosure:

Summary of Results of Flooding Hazard Re-Evaluation Report

cc w/encl: Distribution via Listserv

PKG ML15280A024; LTR: ML15280A022; ENCL: ML15240A362 *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA* NRO/DSEA/RHM1/TR* NRO/DSEA/RHM1/BC* NAME JUribe SLent MLee KErwin(A) DATE 10/5/2015 10/5/15 8/31/2015 8/31/2015 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME MShams JUribe DATE 10/8/2015 10/8/2015

ENCLOSURE:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS