ML15240A183
| ML15240A183 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| 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 | |
| ML15240A189 | List: |
| References | |
| TAC MF6034, TAC MF6035, TAC MF6036 | |
| Download: ML15240A183 (5) | |
Text
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 37 402-2801 September 3, 2015
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNITS 1, 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 (TAC NOS. MF6034, MF6035 and MF6036)
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. ML15072A130), flood hazard reevaluation report (FHRR) submitted by Tennessee Valley Authority (TVA, the licensee) for Browns Ferry Nuclear Plant, Units 1, 2 and 3 (Browns Ferry),
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.
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.
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 Browns Ferry. 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 Browns Ferry 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).
If you have any questions, please contact me at (301) 415-3809 or e-mail at Juan.Uribe@nrc.gov.
Docket Nos. 50-259, 50-260 and 50-296
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv
~~
Juan Uribe, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
ENCLOSURE:
SUMMARY
TABLES OF REEVALUATED FLOOD HAZARD LEVELS
Browns Ferry, Units 1, 2, & 3 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Local Intense Precipitation East Switchyard
! Lower plant area I
West Channel i
I Streams and Rivers L_ -
Failure of Dams and Onsite Water Control/Storage Structures I
Storm Surge I
I Seiche I I I I
Tsunami Ice-Induced Flooding Stillwater Elevation 578.0 ft msl 565.0 ft msl 592.0 ft msl 572.5 ft msl Waves/
Run up Minimal Minimal Minimal 5.5 ft Not included I Not included in DB in DB i
I Not included
! Not included in DB I
in DB i
Not included Not included in DB in DB Design Basis Hazard Elevation I 578.0 ft msl i
I i
565.0 ft msl 592.0 ft msl I
I 578.0 ft msl Not included in DB Not included in DB I
- Not included I
in DB Not included Not included I Not included in DB in DB in DB Not included Not included Not included in DB in DB in DB Reference I
FHRR Section 3.4.1 I
FHRR Section 3.4.1 FHRR Tabel 11-1 FHRR Section 3.4.2 FHRR Section 3.4.8.1 FHRR Section 3.4.3 I
I I I
FHRR Section 3.4.4 I
FHRR Section 3.4.4 I
FHRR Section 3.4.5 FHRR Section 3.4.6 i
I I
I I
I
Browns Ferry, Units 1, 2, & 3 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism T
I Stillwater Elevation i Channel Migrations/Diversions Not included in DB Waves/
Run up Not included in DB Design Basis Hazard Elevation Not included in DB Note: Reported values are rounded to the nearest one-tenth of a foot.
--- -- - -i Reference I
FHRR Section 3.4.7
Browns Ferry, Units 1, 2, & 3 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA
~-- -
I Stillwater Waves/
Elevation Run up Mechanism Local Intense Precipitation
! Switchyard 578.2 ft msl Minimal Lower plant area 566.6 ft msl Minimal
-T-------------,-
- Reevaluated Hazard i
i Elevation 578.2 ft msl 566.6 ft msl Reference FHRR Section 9.1.2 FHRR Section 9.1.2 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 ML15240A189; LTR: ML15240A183; ENCL: ML15226A594 *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 / 28 /15 8 / 28 /15 8 / 17 /15 8 / 17 /15 OFFICE NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME MS hams JUribe DATE 8 / 28 /15 9 / 3 /15