ML15239B292
| ML15239B292 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/03/2015 |
| From: | Juan Uribe Japan Lessons-Learned Division |
| To: | James Shea Tennessee Valley Authority |
| Uribe J, NRR/JLD, 415-3809 | |
| Shared Package | |
| ML15239B287 | List: |
| References | |
| TAC MF5857, TAC MF5858 | |
| Download: ML15239B292 (8) | |
Text
OFFICIAL USE ONLY SECURITY RELATED INFORMATION UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Joseph W. Shea Vice President, Nuclear Licensing Tennessee Valley Authority 1101 Market Street, LP 3R-C Chattanooga, TN 37402-2801 September 3, 2015
SUBJECT:
WATTS BAR NUCLEAR PLANT, 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 (TAC NOS. MF5857 AND MF5858)
Dear Mr. Shea:
The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of the re-evaluated flood-causing mechanisms described in the March 12, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15071A262), flood hazard reevaluation report (FHRR) submitted by Tennessee Valley Authority (TVA, the licensee) for Watts Bar Nuclear Plant, Units 1 and 2 (Watts Bar), 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 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 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. transmitted herewith contains Security-Related Information. When separated from the Enclosure, this document is decontrolled.
OFFICIAb USli ONLY SECURITY RELATED INFORMATION
- oi;i;1c1AL USE ONLY SECURITY RELATED INFORMATION 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 Table 2 includes security-related information, 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 guidance documents currently being finalized by the industry and NRC staff) for Watts Bar. 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.
In addition, 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 Watts Bar 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 SECUR~ELATED INFORMATION
- OFFICIAb USE! ONbY Sl!CURITY RE!bATE!D INFOR~nATION If you have any questions, please contact me at (301) 415-3809 or e-mail at Juan.Uribe@nrc.gov.
Docket Nos. 50-390 and 50-391
Enclosures:
- 1. Summary of Results of Flooding Juan F.
ibe, Project anager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Hazard Re-Evaluation Report (Redacted Version)
- 2. Summary of Results of Flooding Hazard Re-Evaluation Report (NON-PUBLIC) cc w/encl: Distribution via Listserv OFFICIAL USE ONLY SECURITY RELATEE> INFORIUIATIO~
ENCLOSURE 1:
SUMMARY
TABLES OF REEVALUATED FLOOD HAZARD LEVELS-REDACTED VERSION
Watts Bar, Unit 1 and 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/
Design Basis Reference Elevation Run up Hazard Elevation Local Intense Precipitation 728.9 ft MSL Minimal 728.9 ft MSL FHRR Section 3.4.1 Streams and Rivers
- 2) Intake Pumping Station 739.2 ft MSL 2.5 ft 741.7 ft MSL FHRR Section 3.4.2 FHRR Section 3.4.8 Failure of Dams and Onsite Water Control/Storage Structures 731.2 ft MSL Not 731.2 ft MSL FHRR Table 11-1 applicable Storm Surge Not included Not included Not included FHRR Section 3.4.4 in DB in DB in DB Seiche Not included Not included Not included FHRR Section 3.4.4 in DB in DB in DB Tsunami Not included Not included Not included FHRR Section 3.4.5 in DB in DB in DB Ice-Induced Flooding Not included Not included Not included FHRR Section 3.4.6 in DB in DB in DB
Watts Bar, Unit 1 and 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/
Design Basis Reference Elevation Run up Hazard Elevation Channel Migrations/Diversions Not included Not included Not included FHRR Section 3.4.7 in DB in DB in DB Note: Reported values are rounded to the nearest one-tenth of a foot.
Watts Bar, Unit 1 and 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism Stillwater Waves/
Reevaluated Reference Elevation Run up Hazard Elevation Local Intense Precipitation 729.2 ft MSL Minimal 729.2 ft MSL FHRR Table 11-1 Streams and Rivers
[Redacted]
[Redacted]
[Redacted]
[Redacted]
[Redacted]
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 ML152398287; LTR: ML152398292; ENCL 1: ML15226A597 PUBLIC) *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM1/TR*
NRO/DSEA/RHM2/BC*
NAME JUribe Slent SBreithaupt ARiveraVarona DATE 8/27/15 8/27/15 8/17/15 8/17/15 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME MShams JUribe DATE 8 / 28 /15 9 / 3 /15