ML15211A482
| ML15211A482 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 09/03/2015 |
| From: | Tekia Govan Japan Lessons-Learned Division |
| To: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| Minarik A, NRR/JLD, 415-6185 | |
| References | |
| TAC MF3655, TAC MF3656 | |
| Download: ML15211A482 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.c: 20555-0001 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 September 3, 2015
SUBJECT:
LASALLE COUNTY STATION, 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. MF3655 AND MF3656)
Dear Mr. Hanson:
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, 2014 (Agencywide Document Access and Management System (ADAMS) Accession No. ML14079A417), flood hazard reevaluation report (FHRR) submitted by Exelon Generation Company, LLC (Exelon, the licensee) for LaSalle County, Units 1 and 2 (LaSalle), 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 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 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 COM-SECY-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 flood hazard 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 LaSalle. 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 LaSalle 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 NRC letter, "Coordination of Request for Information Regarding Flooding Hazard Reevaluation and Mitigating Strategies for Beyond Design Bases 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 forthe Reevaluation of Flooding Hazards for Operating Nuclear Power Plants" (ADAMS Accession No. ML15209A682).
If you have any questions, please contact me at (301) 415-6197 or e-mail at Tekia.Govan@nrc.gov.
Docket Nos. 50-373 and 50-37 4
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv Tekia Govan, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
ENCLOSURE:
SUMMARY
TABLES OF REEVALUATED FLOOD HAZARD LEVELS
LaSalle, Units 1 & 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 LIP Zone 1 (North portion of site) 710.1 ft MSL Not 710.1 ft MSL FHRR Section 2.2.1 applicable LIP Zone 2 (South portion of site) 710.3 ft MSL Not 710.3 ft MSL FHRR Section 2.2.1 applicable Streams and Rivers Riverine 521.8 ft MSL 0.7 ft 522.5 ft MSL USFAR Revision 19 Section 2.4.3 FHRR Section 2.2.2 Failure of Dams and Onsite I
Water Control/Storage Structures No impact on No impact on No impact on the site the site the site FHRR Section 2.2.3 identified identified identified Storm Surge PMF on Lake at Dike 704.3 ft MSL 2.9 ft 707.2 ft MSL FHRR Section 2.2.4 PMF on Cooling Lake at Plant 704.3 ft MSL 1.3 ft 705.6 ft MSL FHRR Section 2.2.4 PMF on Cooling Lake at Lake 704.3 ft MSL 1.8 ft 706.1 ft MSL FHRR Section 2.2.4 Screen House Seiche Not included Not included Not included FHRR Section 2.2.5 in DB in DB in DB Tsunami Not included Not included Not included FHRR Section 2.2.6 in DB in DB in DB
LaSalle, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA r-- ****----------------------
**--*~------------*------- --------****
Mechanism Stillwater Waves/
Design Basis Reference i
Elevation Run up Hazard I
Elevation Ice-Induced Flooding No impact on No impact on No impact on the site the site the site FHRR Section 2.2.7 identified identified identified Channel Migrations/Diversions i
No impact on No impact on No impact on the site the site the site FHRR Section 2.2.8 identified identified identified Note: Reported values are rounded to the nearest one-tenth of a foot.
LaSalle, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA
-I Stillv,;,-a-te_r_~*-***-w-a_v_e_s_/
~1-R_e_e-va_l_u._a te-d~--- _____
R
___ e
___ fe_r_e-nc_e ____ -------------
Elevation Run up Hazard Elevation i---------------t------+------+-------+-------------~-~
I Local Intense Precipitation I
I 1
~-
Mechanism
! LIP for entire site 710.8 MSL Minimal 710.8 MSL FHRR Section 3.1
! Storm Surge j Lake screen house 701.0 MSL 9.6 ft 710.6 MSL FHRR Section 3.4.4 I
i
' I Inlet structure 701.0 MSL 11.0 ft 712.0 MSL FHRR Section 3.4.4 I
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) 415-6197 or e-mail at Tekia.Govan@nrc.gov.
Sincerely,
/RN Tekia Govan, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-373 and 50-37 4
Enclosure:
Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv DISTRIBUTION:
PUBLIC TGovan, NRR RidsNrrDorllpl3-2 Resource RidsRgn3MailCenter Resource RidsOpaMail Resource ARivera-Varona, NRO MWillingham, NRO MShams, NRR JLD R/F LQuinn-Willingham, NRO RidsNrrDorl Resource RidsN rrLASLent RidsAcrsAcnw_MailCtr Resource KErwin, NRO RRivera-Lugo, NRO RidsNRRJLD Resource RidsNroDsea Resource RidsNrrPMLaSalle Resource RidsOgcMailCenter Resource CCook, NRO ACampbell, NRO BHarvey, NRO ADAMS A N
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via ema1 OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM2/TR NRO/DSEA/RHM2/BC*
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