ML16286A161
| ML16286A161 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/17/2016 |
| From: | Lauren Gibson Japan Lessons-Learned Division |
| To: | Northard S Northern States Power Company, Minnesota |
| Gibson L, NRR/JLD 301-415-1056 | |
| Shared Package | |
| ML16248A005 | List: |
| References | |
| CAC MF7710, CAC MF7711 | |
| Download: ML16286A161 (5) | |
Text
Mr. Scott D. Northard Acting Vice President UNITED ST ATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 17, 2016 Northern States Power Company - Minnesota Prairie Island Nuclear Generating Plant 1717 Wakonade Drive East Welch, MN 55089-9642
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 -
CORRECTION TO INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST-FLOOD-CAUSING MECHANISM REEVALUATION (CAC NOS. MF7710 AND MF7711)
Dear Mr. Northard:
By letter dated September 16, 2016 (Agencywide Document Access and Management System (ADAMS) Accession No. ML16248A005), the U.S. Nuclear Regulatory Commission transmitted to you the Interim Staff Response to the reevaluated flood hazards for Prairie Island Nuclear Generating Plant, Units 1 and 2 (Prairie Island). In that letter, the second page was inadvertently omitted from the electronic version. This letter supersedes the September 16, 2016, letter with the only change being the inclusion of the second page of the cover letter.
The purpose of this letter is to provide a summary of the NRC's staff's assessment of the reevaluated flood-causing mechanisms described in the May 9, 2016 (ADAMS Accession No. ML16133A041 ), flood hazard reevaluation report (FHRR) submitted by Northern States Power Company, a Minnesota corporation (the licensee), doing business as Xcel Energy, for Prairie Island, as well as supplemental information resulting from the NRC's audit of the FHRR.
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. 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 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 NRC's review in the tables provided as an enclosure 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.
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 Prairie Island. 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 Nuclear Energy Institute (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'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) 415-1056 or e-mail at Lauren.Gibson@nrc.gov.
Docket Nos. 50-282 and 50-306
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv Sincerely, c1~
l<d A:tr~
Lauren K. Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
ENCLOSURE:
SUMMARY
TABLES OF REEVALUATED FLOOD HAZARD LEVELS
Prairie ls/and Nuclear Generating Plant, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/ JDeJign Basis Reference Elevation Run up Hazard levation Local Intense Precipitation i
' I Not included Not included Not included FHRR Sections 1.5, 2.1.3 & Table 4 in DB in DB in DB i
I i
Streams and Rivers I
Mississippi River Probable 703.6 ft 3.1 ft 706.7 ft FHRR Section 1.5.1 & Table4 Maximum Precipitation NGVD29 NGVD29 Failure of Dams and Onsite Water Control/Storage Structures 676.5 ft Not 676.5 ft FHRR Section 1.5.2 & Table 4 NGVD29 applicable NGVD29 i
~---
Storm Surge I
Not included Not included Not included FHRR Section 1.5 & Table 4 i
I
--+--*
i
- ------- **----------------------*----+-------
--~
- 1 Seiche i
I Not included Not included Not included FHRR Section 1.5 & Table 4 I
in DB in DB in DB I i Tsunami Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB Ice-Induced Flooding Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB i
Channel Migrations/Diversions Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB Note 1: Reported values are rounded to the nearest one-tenth of a foot.
Prairie Island Nuclear Generating Plant, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA
---.. -~---
---*----------*------~-----------------------*- *~--
Mechanism Local Intense Precipitation Stillwater Elevation 695.4 ft NGVD29 Waves/
Run up Minimal Reevaluated Hazard Elevation 695.4 ft NGVD29 Reference FHRR Section 2.1.2 & Tables 4 and 5 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 ML16248A005; LTR: ML16248A006; ENCL: ML16245A763 (Correction ML16286A161)
- via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM2/TR*
N RO/DSEA/RH M2/BC*
NAME LKGibson Slent PChaput ARiveraVarona DATE 10/17/16 10/14/16 09/1 /2016 09/ 1 /2016 OFFICE NRR/JLD/JHMB/BC (A)
NRR/JLD/JHMB/PM NAME GBowman LKGibson DATE 10/17/16 10/17/16