ML16083A551

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood-Causing Mechanism Reevaluation

ML16083A551
Person / Time
Site:	Diablo Canyon
Issue date:	03/30/2016
From:	Victor Hall Japan Lessons-Learned Division
To:	Halpin E Pacific Gas & Electric Co
Shared Package
ML16083A552	List: ML16083A551 ML16084A610
References
CAC MF6039, CAC MF6040
Download: ML16083A551 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 30, 2016 Mr. Edward D. Halpin Senior Vice President and Chief Nuclear Officer Pacific Gas and Electric Company P.O. Box 56 Mail Code 104/6 Avila Beach , CA 93424

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NOS . 1 AND 2 - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION (CAC NOS. MF6039 AND MF6040)

Dear Mr. Halpin:

The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of the re-evaluated flood-causing mechanisms described in the March 11 , 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15071A045), flood hazard reevaluation report (FHRR) submitted by Pacific Gas and Electric Company (PG&E, the licensee) for Diablo Canyon Power Plant, Unit Nos. 1 and 2 (Diablo Canyon), as well as supplemental information resulting from requests for additional information and audits.

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.

E. Halpin 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 informati.on described in Nuclear Energy Institute (NEI) guidance document NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide") for Diablo Canyon. 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 plans to issue a staff assessment documenting the basis for these conclusions at a later time .

Revision 2 of NEI 12-06 includes a methodology to perform a Mitigating Strategies Assessment (MSA) with respect to the reevaluated flood hazards. On February 29, 2016, the NRC staff published Japan Lessons-Learned Division Interim Staff Guidance (ISG) JLD-ISG-2012-01 ,

Revision 1, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," (ADAMS Accession No. ML15357A142) in the Federal Register(81FR10283). This ISG endorses Revision 2 of NEI 12-06 (ADAMS Accession No. ML16005A625), dated December 2015.

Based on the guidance provided in Revision 2 of the NEI 12-06 guidance document, flood event duration parameters and applicable flood associated effects should be considered as part of the Diablo Canyon 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).

E. Halpin If you have any questions, please contact me at (301) 415-2915 or e-mail at Victor.Hall@nrc.gov.

Victor Hall, Senior Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323

Enclosure:

Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl : Distribution via Listserv

ENCLOSURE:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Diablo Canyon Nuclear Power Plant, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/ Design Basis Reference Elevation Run up Hazard Elevation I

Local Intense Precipitation I

I No Impact No Impact No Impact FHRR Section 2.3.2.1

on the Site on the Site on the Site Identified Identified Identified I

I i

I Streams and Rivers i Diablo Creek 81 .9 ft. Not 81 .9 ft. FHRR Section 2.3.2.2 NAVD88 applicable NAVD88 I

Failure of Dams and Onsite I Water I

Control/Storage Structures I

I No Impact No Impact No Impact FHRR Section 2.3.2 .3 I on the Site on the Site on the Site Identified Identified Identified I Storm Surge II I Storm Surge No Impact No Impact No Impact FHRR Section 2.3 .2.4 I on the Site on the Site on the Site Identified Identified Identified I

I Seiche No Impact No Impact No Impact FHRR Section 2.3.2.5 on the Site on the Site on the Site Identified Identified Identified I

Tsunami I

' Distantly-Generated Tsunamis 20 .0 ft. 10.3ft 30 .3 ft. FHRR Section 2.3.2.6.1 NAVD88 NAVD88 I

FHRR Section 2.3.2.13 I

I I Near-Shore Tsunamis 9.2 ft. 25.7 ft 34 .9 ft. FHRR Section 2.3.2.6.2 NAVD88 NAVD88 FHRR Section 2.3.2.13 I

!I Ice-Induced Flooding I

I I Not included Not included Not included FHRR Section 2.3.2 .7 I

I I

in DB in DB in DB I

I

Diablo Canyon Nuclear Power Plant, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA

- ------ - -- -- - ~

Mechanism ,Stillwater Waves/ Design Basis Reference Elevation Run up Hazard Elevation Channel Migrations/Diversions Not included Not included Not included FHRR Section 2.3.2.8 in DB in DB in DB I

Note 1: Reported values are rou nded to the nearest one-tenth of a foot.

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Diablo Canyon Nuclear Power Plant, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism Stillwater Waves/ Reevaluated Reference Elevation Run up Hazard Elevation Local Intense Precipitation Door/Unit No. A2 .1 87.4 ft. Minimal 87.4 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No. BU102 87.4 ft. Minimal 87.4 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Un it NoBU103 87.3 ft. Minimal 87.3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoA3.1 87.4 ft. Minimal 87.4 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoA3.2 87.4 ft. Minimal 87.4 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoA3.3 87.3 ft. Minimal 87.3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoBU104/5 87.3 ft. Minimal 87.3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.101-1 87.7 ft. Minimal 87.7 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Un it No.102-1 87 .7 ft. Minimal 87.7 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.119-1 87 .9 ft. Min imal 87 .9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.122-1 88 .1 ft. Minimal 88.1 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88

Diablo Canyon Nuclear Power Plant, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA I

Mechanism Stillwater Waves/ Reevaluated Reference Elevation Run up Hazard Elevation Door/Unit No.C1 .1 87 .6 ft. Minimal 87 .6 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.1 29 87.6 ft. Minimal 87 .6 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No .1 30 87 .5 ft. Minimal 87 .5 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.C1 .2 87 .7 ft. Minimal 87.7 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoBU108-2 87 .3 ft. Minimal 87 .3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No BU 105-2 87.3 ft. Minimal 87.3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoBU106-2 87.5 ft. Minimal 87.5 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoB2.1 87 .6 ft. Minimal 87 .6 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No. BU101 87.3 ft. Minimal 87.3 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoB1 .1 87 .6 ft. Minimal 87 .6 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit NoB1 .2 87 .6 ft. Minimal 87 .6 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No .101-2 87 .8 ft. Min imal 87.8 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 2

Diablo Canyon Nuclear Power Plant, Units I & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism Stillwater Waves/  ! Reevaluated Reference Elevation Run up Hazard Elevation Door/Unit No.102-2 87.8 ft. Minimal 87 .8 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.119-2 87 .9 ft. Minimal 87 .9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.122-2 88.0 ft. Minimal 88 .0 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.192-1 88.2 ft. Minimal 88.2 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.191-1 88 .0 ft. Minimal 88.0 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No .194-1 88 .0 ft. Minimal 88.0 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Un it No.192-2 88.1 ft. Minimal 88.1 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.191-2/191 A-2 88.0 ft. Minimal 88.0 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No.194-2 87.9 ft. Minimal 87.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No363-1 117.6 ft. Minimal 117.6ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No361-1 117.9 ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No360-1 117.9 ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 3

Diablo Canyon Nuclear Power Plant, Units 1 & .2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism Stillwater Waves/  ! Reevaluated Reference Elevation Run up Hazard Elevation Door/Unit No355-1 117.9 ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No354-1 117.9 ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No360-2 117.9ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No361 -2 117.9ft. Minimal 117.9 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Door/Unit No363-2 117.5 ft. Minimal 117.5 ft. FHRR Enclosure 1 Table 3-5 NAVD88 NAVD88 Note 1: The licensee is expected to develop flood event duration parameters and applicable flood associated effects to conduct the MSA. The staff will evaluate the flood event duration parameters (including warning time and period of inundation) and flood associated effects during its review of the MSA.

Note 2: Reevaluated hazard mechanisms bounded by the current design basis (see Table 1) are not included in this table Note 3: Reported values are rounded to the nearest one-tenth of a foot.

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PKG: ML16083A552; LTR: ML16083A551; ENCL: ML16084A610 *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSENRHM1/TR* NRO/DSENRHM2/BC*

NAME VHall Slent KQuinlan ARivera-Varona DATE 03/22/16 03/24/16 03/25/16 03/25/16 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME MS hams VHall DATE 03/30/16 03/30/16