ML16267A131
| ML16267A131 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/13/2016 |
| From: | Lauren Gibson Japan Lessons-Learned Division |
| To: | Heacock D Dominion Nuclear |
| Sebrosky NRC/NRR/JLD 301-415-1132 | |
| Shared Package | |
| ML16267A170 | List: |
| References | |
| TAC MF6109, TAC MF6110 | |
| Download: ML16267A131 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. David A. Heacock President and Chief Nuclear Officer Dominion Nuclear Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711 October 13, 2016
SUBJECT:
MILLSTONE 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. MF6109, AND MF6110)
Dear Mr. Heacock:
The purpose of this letter is to provide a partial 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. ML15078A203}, flood hazard reevaluation report (FHRR) submitted by Dominion Nuclear Connecticut, Inc. (the licensee) for Millstone Power Station, Unit Nos. 2 and 3 (MPS2 and MPS3), as well as supplemental information resulting from audits. The staff's review of the storm surge flooding mechanism continues and future correspondence with you on this mechanism will be forthcoming.
By letter dated March 12, 2012, the NRC issued a request for information pursuant to Title 1 O 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 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 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. Because of the difference in the licensing basis and the elevations for MPS2 and MPS3, there is a Table 1 and Table 2 for each site.
The attached tables do not include the staff's assessment of flooding due to storm surge. The staff's evaluation of this mechanism is continuing and future correspondence documenting the results of the staff's review will be forthcoming. For other flood causing mechanisms, 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 MPS2 and MPS3. 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, dated December 2015, 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). 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 MPS2 and MPS3 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, each 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). The staff notes that a separate integrated assessment or focused evaluation for the storm surge flooding mechanism maybe needed based on the results of the staff's review.
If you have any questions, please contact me at (301) 415-1056 or e-mail at Lauren.Gibson@nrc.gov.
Docket Nos. 50-336 and 50-423
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv Sincerely, Lauren Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
Table 1. Millstone Power Station, Unit 2: Current Design Basis Flood Hazards for Use in the MSA Mechanism Stlllwa~ves/
Design Basis I Reference Elevation Run up Hazard Elevation Local Intense Precipitation 14.5 ft Minimal 14.5ft FHRR Table 1.2-1 NGVD29 NGVD29 Streams and Rivers No Impact No Impact No Impact FHRR Table 1.2-1 on the Site on the Site on the Site Identified Identified Identified Failure of Dams and Onsite Water Control/Storage Structures Not included Not included Not included FHRR Sections 2.3.3 & 3.3 in DB in DB in DB Storm Surge Storm Surge within the Intake 26.5 ft Not 26.5 ft FHRR Table 1.2-1 Structure for Unit 2 NGVD29 applicable NGVD29 Storm Surge at the Powerblock 21.3 ft 3.8 ft 25.1 ft FHRR Table 1.2-1 NGVD29 NGVD29 Seiche No Impact No Impact No Impact FHRR Table 1.2-1 on the Site on the Site on the Site Identified Identified Identified Tsunami Not included Not included Not included FHRR Table 1.2-1 in DB in DB in DB Ice-Induced Flooding No Impact No Impact No Impact FHRR Table 1.2-1 on the Site on the Site on the Site Identified Identified Identified I
Table 1. Millstone Power Station, Unit 2: Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/
Design Basis Reference Elevation Run up Hazard Elevation Channel Migrations/Diversions No Impact No Impact No Impact FHRR Table 1.2-1 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.
Table 2. Millstone Power Station, Unit 2: Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA I
Mechanism I
Local Intense Precipitation Streams and Rivers Storm Surge Tsunami Stillwater Elevation 17.5 ft NGVD29 11.2 ft NGVD29 Under Review
- 14. 7 ft NGVD29 Waves/
Run up Minimal Not applicable Under Review Not applicable Reevaluated Hazard Elevation 17.5 ft NGVD29 11.2 ft NGVD29 Under Review
- 14. 7 ft NGVD29 Reference FHRR Section 3.1 FHRR Section 2.2 FHRR Section 2.6 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.
Table 1. Millstone Power Station, Unit 3: Current Design Basis Flood Hazards for Use in the MSA Mechanism Local Intense Precipitation Auxiliary Building Door A-24-1 Control Building Emergency Generator Enclosure Demineralized Water Storage Tank Block House Fuel Building Auxiliary Building Door A-24-6 Engineered Safety Features Building Main Steam Valve Building Valve Enclosure Hydrogen Recombiner Building Streams and Rivers Stillwater Elevation 24.9 ft NGVD29 24.3 ft NGVD29 24.3 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 No Impact on the Site Identified Waves/
Run up Minimal Minimal Minimal Minimal Minimal Minimal Minimal Minimal Minimal Minimal No Impact on the Site Identified Design Basis Hazard Elevation 24.9 ft NGVD29 24.3 ft NGVD29 24.3 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 24.9 ft NGVD29 No Impact on the Site Identified Reference FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-3 FHRR Table 1.2-2
Table 1. Millstone Power Station, Unit 3: Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/ 1*sign Basis Reference Elevation Run up Hazard Elevation Failure of Dams and Onsite Water Control/Storage Structures Not included Not included Not included FHRR Sections 2.3.3 & 3.3 in DB in DB in DB Storm Surge Storm Surge at Seaward Wall of 41.2 ft Not 41.2 ft FHRR Table 1.2-2 Intake Structure for Unit 3 NGVD29 applicable NGVD29 Storm Surge at Powerblock 19.?ft 4.1 ft 23.8 ft FHRR Table 1.2-2 NGVD29 NGVD29 Seiche No Impact No Impact No Impact FHRR Table 1.2-1 on the Site on the Site on the Site Identified Identified Identified Tsunami Not included Not included, Not included FHRR Table 1.2-2 in DB in DB in DB Ice-Induced Flooding No Impact No Impact No Impact FHRR Table 1.2-1 on the Site on the Site on the Site Identified Identified Identified Channel Migrations/Diversions No Impact No Impact No Impact FHRR Table 1.2-1 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.
Table 2. Millstone Power Station, Unit 3: Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism I Stillwater Waves/
Reevaluated I
Elevation Run up Hazard Elevation Reference Streams and Rivers 11.2 ft Not 11.2 ft FHRR Section 2.2 NGVD29 applicable NGVD29 Storm Surge Under Under Under Review Review Review 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.
If you have any questions, please contact me at (301) 415-1056 or e-mail at Lauren.Gibson@nrc.gov.
Sincerely, IRA/
Lauren Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-336 and 50-423
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv DISTRIBUTION:
PUBLIC LGibson, NRR RidsNrrDorllpl1-2 Resource RidsRgn1 MailCenter Resource RidsOpaMail Resource ARivera-Varona, NRO MWillingham, NRO MShams, NRR JLD R/F LQuinn-Willingham, NRO RidsNrrDorl Resource RidsNrrLASLent RidsAcrsAcnw_MailCtr Resource KErwin, NRO LHibler, NRO RRivera-Lugo, NRO RidsNRRJLD Resource RidsNroDsea Resource RidsNrrPMMillstone Resource RidsOgcMailCenter Resource CCook, NRO ACampbell, NRO BHarvey, NRO GBowman, NRR ADAMS Accession Nos.: PKG ML16267A170 LTR: ML16267A131 ENCL: ML16267A168 *via email OFFICE NRR/JLD/JHMB/PM*
NRR/JLD/LA NRO/DSENRHM2/TR*
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DATE 9/30/16 9/30/2016 9/22/2016 OFFICE NRO/DSENRHM2/BC*
NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME ARiveria-Varona GBowman LGibson DATE 10/11/2016 10/13/2016 10/13/2016 OFFICIAL AGENCY RECORD