ML16337A109

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

ML16337A109
Person / Time
Site:	Columbia
Issue date:	12/07/2016
From:	Lauren Gibson Japan Lessons-Learned Division
To:	Reddemann M Energy Northwest
Gibson L, NRR/JLD, 415-1056
References
TAC MF3039
Download: ML16337A109 (10)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 7, 2016 Mr. Mark E. Reddemann Chief Executive Officer Energy Northwest MD 1023 76 North Power Plant Loop P.O. Box 968 Richland, WA 99352

SUBJECT:

COLUMBIA GENERATING STATION - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION (CAC NO. MF3039)

Dear Mr. Reddemann:

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 October 6, 2016 (Agencywide Document Access and Management System (ADAMS) Accession No. ML16286A309), flood hazard reevaluation report (FHRR) submitted by Energy Northwest (the licensee) for Columbia Generating Station.

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 that licensees reevaluate flood-causing mechanisms using present-day methodologies and guidance. Concurrent 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 the staff requirements memorandum (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 in its FHRR 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.

M. Reddemann The NRC staff has concluded that the licensee's reevaluated flood hazard 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 Columbia Generating Station.

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 NEI 12-06, flood event duration parameters and applicable flood associated effects should be considered as part of the 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 SAM to COMSECY-15-0019, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants" (ADAMS Accession No. ML15209A682).

M. Reddemann If you have any questions, please contact me at (301) 415-1056 or e-mail at Lauren.Gibson@nrc.gov.

Sincerely, ot~ ;&$, _b,'6:J,,V Lauren K. Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket No. 50-397

Enclosure:

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

ENCLOSURE 1:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Columbia Generating Station Table 1. Current Design Basis Flood Hazards for Use in the MSA 1 Mechanism Stillwater Waves/ Design Basis *.* Reference Elevation Run up Hazard 1 Elevation j Local Intense Precipitation i Not included Not included Not included FHRR Table 3 in DB in DB in DB Streams and Rivers Columbia River2 390.0 ft MSL Minimal 390.0 ft MSL FHRR Table 3 Local Drainage (Combined Effect) 431.1 ft MSL 2.2 ft 433.3 ft MSL FHRR Table 3 Failure of Dams and Onsite Water Control/Storage Structures 2 Combined Effect I 422.0 ft MSL 2 ft 424.0 ft MSL FHRR Table 3 Storm Surge No Impact No Impact No Impact FHRR Table 3 on the Site on the Site on the Site Identified Identified Identified Seiche No Impact No Impact No Impact FHRR Table 3 on the Site on the Site on the Site Identified Identified Identified Tsunami No Impact No Impact No Impact FHRR Table 3 on the Site on the Site on the Site Identified Identified Identified Ice-Induced Flooding No Impact No Impact No Impact FHRR Table 3 the Site on the Site on the Site Identified Identified Identified

Columbia Generating Station Table 1. Current Design Basis Flood Hazards for Use in the MSA 1 Mechanism Stillwater Waves/ Design Basis Reference Elevation Run up Hazard Elevation Channel Migrations/Diversions No Impact No Impact No Impact FHRR Table 3 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.

Note 2: These hazards remain within the Columbia River Basin, a separate sub-basin away from CGS. CGS is not exposed to these hazards due to intervening topography. This remains true for the re-evaluated hazards.

Columbia Generating Station Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA 1*2 Mechanism Stillwater Waves/ Reevaluated Reference l Local Intense Precipitation Elevation Run up Hazard Elevation-High point near Radwaste 441.2 ft MSL Minimal 441.2 ft MSL FHRR Table 1 Building truck ramp DG Building Exterior Door (DG2) ' 440.9 ft MSL Minimal 440.9 ft MSL FHRR Table 1 DG Building Exterior Door (DG1) 440.9 ft MSL Minimal 440.9 ft MSL FHRR Table 1 DG Building Exterior Door 440.9 ft MSL Minimal 440.9 ft MSL ' FHRR Table 1 (HPCS DG)

Reactor Building railroad bay 441.1 ft MSL Minimal 441.1 ft MSL FHRR Table 1 door Service Water B pump house 441.0 ft MSL Minimal 441.0 ft MSL FHRR Table 1 personnel door Service Water B spray pond wall 435.2 ft MSL Minimal 435.2 ft MSL FHRR Table 1 Service Water A pump house Minimal 439.0 ft MSL FHRR Table 1 personnel door Service Water A spray pond wall 435.1 ft MSL Minimal , 435.1 ft MSL FHRR Table 1 Roof drain (storm sewer) header 440.3 ft MSL Minimal 440.3 ft MSL FHRR Table 1 manhole MH-S5 Vehicle Barrier System high point 438.0 ft MSL Minimal 438.0 ft MSL FHRR Table 1

Columbia Generating Station Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA 1*2 Mechanism Stillwater Waves/ Reevaluated Reference Elevation Run up Hazard Elevation 1

Benchmark infront of TSC 440.6 ft MSL Minimal 440.6 ft MSL FHRR Table 1 entrance Benchmark in by NW remote air 441.0 ft MSL Minimal 1 441.0 ft MSL FHRR Table 1 intake Benchmark infront of GSB 440.9 ft MSL Minimal 440.9 ft MSL FHRR Table 1 entrance Benchmark infront of Building 88 440.6 ft MSL Minimal 440.6 ft MSL FHRR Table 1 North Side of Flex Building 82 440.6 ft MSL Minimal 440.6 ft MSL FHRR Table 1 North Side of Flex Building 600 437.8 ft MSL Minimal 437.8 ft MSL FHRR Table 1 South Side of Flex Building 600 438.0 ft MSL Minimal 438.0 ft MSL FHRR Table 1 ISFSI Pad (North) 443.3 ft MSL Minimal 443.3 ft MSL FHRR Table 1 ISFSI Pad (South) 443.3 ft MSL Minimal 443.3 ft MSL FHRR Table 1 Facilities Fuel Station 440.6 ft MSL Minimal 440.6 ft MSL FHRR Table 1 Diesel Generator Tank Access 442.1 ft MSL Minimal 442.1 ft MSL FHRR Table 1 Flex Gasoline Storgae Module 440.8 ft MSL Minimal 440.8 ft MSL FHRR Table 1

Columbia Generating Station Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA 1 *2 Mechanism Stillwater Waves/ Reevaluated Reference Elevation Run up Hazard Elevation Streams and Rivers Local Drainage 432.0 ft MSL Minimal 432.0 ft MSL FHRR Table 3 Note 1: Reevaluated hazard mechanisms bounded by the current design basis (see Table 1) are not included in this table Note 2: Reported values are rounded to the nearest one-tenth of a foot.

PKG ML16337A111; LTR: ML16337A109; ENCL: ML16333A094 *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM2/TR* N RO/DSEA/RH M 1/BC*

NAME LKGibson Slent KSee CCook DATE 12/5/16 12/ 5 /16 11 I 29 /16 11 I 29 /16 OFFICE NRR/JLD/JHMB/BC (A) NRR/JLD/JHMB/PM NAME GBowman LKGibson DATE 12 I 6 /16 12 /7/16