ML15357A517

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

ML15357A517
Person / Time
Site:	Limerick
Issue date:	12/24/2015
From:	Tekia Govan Japan Lessons-Learned Division
To:	Bryan Hanson Exelon Generation Co
Govan, Tekia NRR/JLD 415-6197
Shared Package
ML15357A519	List: ML15357A517
References
CAC MF6107, CAC MF6108
Download: ML15357A517 (8)

Text

OFFICIAb YSe ONLY SECURITY RELATED INFORMATION UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 24, 2015 Mr. Bryan C. Hanson President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

LIMERICK GENERATING STATION, UNITS 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. MF6107 AND MF6108)

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 March 12, 2015 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML15084A586), flood hazard reevaluation report (FHRR) submitted by Exelon Generation Company, LLC (the licensee) for Limerick Generating Station, Units 1 and 2 (Limerick), 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 reevaluate 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

I OFFICIAL USE ONLY SECURITY RELATED INFORMl\TION B. Hanson The NRG staff has reviewed the information submitted by the licensee and has summarized the results of the 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 NRG 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 NRG staff) for Limerick. 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 NRG staff plans 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 Limerick 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

• OFFJCIAL. USi ONbY 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.

lb-6~9 Tekia Govan, Project Manager ~

Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-352 and 50-353

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 OfflCIAL USE ONLY SECURITY RELATED INFORMATION

ENCLOSURE 1:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Limerick Generating Station, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA

---**---Mechan-i~--------,-- Stillwater-. ----WavesT- Design- Basis Ref~rence Elevation Run up Hazard Elevation Local Intense Precipitation Turbine Building 218.6 ft NGVD29 II ~inimal M

218.6ft NGVD29 FHRR Section 2.2.1 & Table 4.0.2 Diesel Generator Building

• Not included Not included Not included FHRR Section 2.2.1 & Transmittal in DB in DB in DB Letter j

Streams and Rivers i Schuylkill River 174.0 ft No Impact 174.0 ft FHRR Section 2.2.2 NGVD29 on the Site NGVD29 Identified Sanatoga Creek No Impact No Impact No Impact FHRR Section 2.2.1 I on the Site on the Site on the Site Identified Identified Identified No Impact Possum Hollow Run 159.0 ft on the Site 159.0 ft FHRR Section 2.2.1 & Table 4.0.3 I NGVD29 Identified NGVD29 I

I I

[Redact~]T .

I

-t--* -*- ------ -**-***

Failure of Dams and Onsite Water Control/Storage Structures

[Redacted) [Redacted) [Redacted] [Redacted)

I Storm Surge No Impact No Impact No Impact FHRR Section 2.2.4 on the Site on the Site on the Site I

Identified Identified Identified I I Seiche No Impact No Impact No Impact FHRR Section 2.2.4 on the Site on the Site on the Site Identified Identified Identified I

Tsunami No Impact No Impact No Impact FHRR Section 2.2.5 on the Site on the Site on the Site Identified Identified Identified

Limerick Generating Station, Units r & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA

---

Mechanism * * * - ~~~::~~* - ~~~~~--r*~~~~~:*i* Reference Elevation i

---

-----~ *~-----~

l Ice-Induced Flooding i No Impact No Impact No Impact FHRR Section 2.2.6 i on the Site on the Site on the Site Identified Identified Identified Channel Migrations/Diversions

• 1 No Impact No Impact No Impact FHRR Section 2.2.7 1

on the Site on the Site on the Site Identified Identified Identified Note 1: Reported values are rounded to the nearest one-tenth of a foot.

Limerick Generating Station, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism

,---*--**----~----**

Stillwater Waves/ Ree~aluated _______Reference--------------,

1 I Elevation ' Runup Hazard I Elevation Local Intense Precipitation Diesel Generator Building 217.1 ft Minimal 217.1 ft FHRR Section 3.1.3 & Transmittal NGVD29 NGVD29 Letter 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.

PKG: ML15357A519; LTR: ML15357A517; ENCL 1: ML15355A534 (PUBLIC); ENCL 2:

ML15355A531 (NON-PUBLIC) *via email OFFICE NRR/JLD/JHMB/PM* NRR/JLD/LA NRO/DSEA/RHM1/TR* NRO/DSEA/RHM1/BC*

NAME TGovan SLent WSharp CCook DATE 12 / 24 /2015 12 / 23 /2015 12/21/2015 12/21/2015 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM TGovan (MShams NAME MShams for)

DATE 12 / 24 /2015 12 / 24 /2015