ML16091A136

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request- Flood-causing Mechanism Reevaluation (CAC Nos. MF6598 and MF6599)

ML16091A136
Person / Time
Site:	Peach Bottom
Issue date:	03/31/2016
From:	Tekia Govan Japan Lessons-Learned Division
To:	Bryan Hanson Exelon Nuclear
Tekia Govan, NRR/JLD/JHMB 415-6197
Shared Package
ML16091A120	List: ML16089A353 ML16091A136
References
CAC MF6598, CAC MF6599
Download: ML16091A136 (7)

Text

OFFICIAL USE ONLY ~°'§'fA~TED INFORMATION NUCLEAR REGULATORY COMMISSION WASHINGTON , D.C. 20555-0001 March 31, 2016 Mr. Bryan C. Hanson President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3- INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST- FLOOD-CAUSING MECHANISM REEVALUATION (CAC NOS. MF6598 AND MF6599)

Dear Mr. Hanson :

The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of the reevaluated flood-causing mechanisms described in the August 12, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15233A067), flood hazard reevaluation report (FHRR) submitted by Exelon Generation Company, LLC (the licensee) for Peach Bottom Atomic Power Station, Units 2 and 3 (Peach Bottom), 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.

Enclosure two transmitted herewith contains Security-Related Information. When separated from the Enclosure, this document is decontrolled.

OFFICIAL USE ONLY SECURITY RELATED INFORMATION

OFFICIAL USE ONLY SECURITY RELATED INFORMATION B. Hanson The NRC staff has reviewed the information submitted by the licensee and has summarized the results of t~e review in the tables provided as Enclosure 1 to this letter. Table 1 provides the current design-basis flood hazard mechanisms. Table 2 provides reevaluated flood hazard mechanisms; however, reevaluated hazard mechanisms bounded by the current design-basis (Table 1) are not included. Because Table 2 includes security-related information, Enclosure 1 contains the redacted version of Table 2. Enclosure 2 is withheld from public disclosure and restores the security-related information to Table 2.

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 Nuclear Energy Institute (NEI) guidance document NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide") for Peach Bottom . 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 (JLD) 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 (81 FR 10283). 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 Peach Bottom 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).

OFFICIAL USE ONLY SECURITY RELATED INFORMATION

OFFICIAL USE ONL'f SECURITY RELATED INFORMATION B. Hanson If you have any questions, please contact me at (301) 415-6197 or e-mail at Tekia .Govan@nrc.gov.

~=t+lll ~

Tekia Govan, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-277 and 50-278

Enclosures:

1. Summary of Results of Flooding Hazard Re-Evaluation Report (Redacted Version)

2. Summary of Results of Flooding Hazard Re-Evaluation Report (Non-Public Version) cc w/encl : Distribution via Listserv

< OFFICIAL USE ONLY SECURITY RELATED INFORMATION

OFFICIAL USE ONLY SECURITY RELATED INFORMATION ENCLOSURE 1:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

[REDACTED VERSION]

OFFICIAL USE ONLY SECURITY RELATED INFORMATION

Peach Bottom Atomic Power Station , Units 2 & 3 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 Not included Not included I Not included FHRR Section 2.3.1 in DB in DB I in DB

_______l --

Streams and Rivers II Probable Maximum Flooding Not included Not included  ! Not included FHRR Section2.3.2.2 from Rock Run Creek in DB in DB I in DB Probable Maximum Flooding 131.4ft Not 131.4ft FHRR Section 2.3.2 .1 from Susquehanna River NAVD88 applicable NAVD88 REDACTED REDACTED REDACTED REDACTED REDACTED I

I I

Failure of Dams and Onsite Water Control/Storage Structures REDACTED REDACTED REDACTED REDACTED REDACTED Storm Surge Not included Not included Not included FHRR Section 2.3.4 in DB in DB in DB I

Seiche Not included Not included Not included FHRR Section 2.3.5 in DB in DB in DB I

Tsunami I

Not included Not included Not included FHRR Section 2.3.6 in DB in DB in DB

_]

Peach Bottom Atomic Power Station, Un its 2 & 3 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater I Waves/ Design Basis Reference Elevation I Run up Hazard Elevation Ice-Induced Flooding Not included Not included Not included FHRR Section 2.3.7 in DB in DB in DB Channel Migrations/Diversions Not included Not included Not included FHRR Section 2.3.8 in DB in DB in DB Note 1: Reported values are rounded to the nearest one-tenth of a foot.

PKG: ML16091A120; LTR: ML16091A136ENCL1: ML16089A353 (PUBLIC);

ENCL2: ML16089A364 (NON-PUBLIC) *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSENRHM1/TR* NRO/DSENRHM1 /BC*

NAME TGovan Slent KSee CCook DATE 3/ 31/2016 3/ 31/2016 03/29/16 03/29/16 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME MShams TGovan (JUribe for)

DATE 3/ 31/2016 3/ 31/2016