ML15040A640

LRA - Draft SAMA RAIs

ML15040A640
Person / Time
Site:	Fermi
Issue date:	01/23/2015
From:	Office of Nuclear Reactor Regulation
To:
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Download: ML15040A640 (7)

Text

1 Fermi2LRANPEm Resource From:

Wentzel, Michael Sent:

Friday, January 23, 2015 4:18 PM To:

Randall D Westmoreland (westmorelandr@dteenergy.com)

Subject:

Draft SAMA RAIs Attachments:

Fermi 2 SAMA Clarification RAIs.docx

Randy, As discussed, here are the draft SAMA RAIs.

Thanks, Mike Michael Wentzel Project Manager NRR/DLR/RPB2 (301) 415-6459 michael.wentzel@nrc.gov

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43 Mail Envelope Properties (Michael.Wentzel@nrc.gov20150123161800)

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Draft SAMA RAIs Sent Date:

1/23/2015 4:18:15 PM Received Date:

1/23/2015 4:18:00 PM From:

Wentzel, Michael Created By:

Michael.Wentzel@nrc.gov Recipients:

"Randall D Westmoreland (westmorelandr@dteenergy.com)" <westmorelandr@dteenergy.com>

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Enclosure FERMI 2 SEVERE ACCIDENT MITIGATION ALTERNATIVES (SAMA)

REQUESTS FOR ADDITIONAL INFORMATION (RAI)

By letter dated January 9, 2015, DTE Electric Company (DTE) submitted its responses to U.S.

Nuclear Regulatory Commission (NRC) staffs requests for additional information (RAIs) pertaining to the SAMA review for the Fermi 2 license renewal application. The following RAIs request additional clarification of information provided in your January 9, 2015 letter.

RAI 1 (relating to response to RAI 1.c.iii)

What is the value for the phenomenological failure probability of the common cause failure of all four combustion turbine generators in the event of a weather centered loss of the 345kV (Division 2) Switchyard?

RAI 2 (relating to response to RAI 2.e)

The SAMA analysis release category frequency is based upon a truncation of 1E-12/yr which results in undercounting the Class II frequency by 3.14E-09/yr compared to the Class II frequency from the Level 1 quantification. This is stated to have been resolved by lowering the truncation to 1E-14/yr. It is stated that this 3.14E-09/yr difference was added to the PRA documentation release category (RC) medium/early (M/E) frequency but not that used in the SAMA analysis. Discuss the basis for assigning this undercounting due to truncation to RC M/E and not other RCs such as high/early (H/E) and the impact of not including these truncated out Class II cutsets in the evaluation of the benefit for the SAMAs.

RAI 3 (relating to response to RAI 2.g.iii)

The RAI response provided a wealth of information supporting the selection of representative sequences in terms of the determination of the base case risk, however, the impact of representative selection on the calculation of delta risk for a SAMA is not specifically addressed.

Furthermore, the information provided indicates that the specific example in the RAI will not adversely impact the selection of cost-beneficial SAMAs; however, it does raise concern about the impact of combining Class IIA sequences with Class IV sequences. As indicated in the RAI response, separating the Class IIA sequences from the Class IV sequences in the H/E release category results in a 15% increase in dose risk and a 0.6% increase in OECR in the total risk.

Table 2.g-4 indicates the revised Class II contribution is 2.69 times the person-rem/yr and 1.08 times the OECR contributions when they are included in the H/E base case release category.

Thus, the staff believes, the benefit of any SAMA that significantly reduces the risk of Class IIA (loss of containment heat removal) sequences will be underestimated. Please address the impact of combining Class IIA sequences with Class IV sequences and clarify the impact of representative selection on the calculation of delta risk for a SAMA.

RAI 4 (relating to response to RAI 4.c)

The economic multiplier stated in the RAI response is 2.1384, which is different from the value of 1.2964 stated on page D-96 of the environmental report (ER). The RAI response does not mention any reason for different values. Please clarify which is the correct value for the economic multiplier value used in the assessment of cost beneficial SAMAs.

Enclosure RAI 5 (relating to responses to RAIs 5.a.ii, 5.a.vi, 5.a.vii, 6.h and 7.a)

The response to these RAIs provides the result of new cost benefit analyses. Was this based on doing the complete analysis similar to that for the ER evaluation involving determining the new release category frequencies and resulting cost risks, or were some other assumptions made?

Some of the results do not appear to be consistent with those given in Table D.2-1 for similar SAMAs.

RAI 6 (relating to response to RAI 6.c)

While Fermi 2 may not have the same vulnerability that prompted SAMA 023 to develop procedures to repair or replace failed 4 kV breakers, this SAMA was cited to mitigate a number of important Fermi events in Table D.1-2 and screening it out is not considered appropriate.

Evaluate the benefit of a procedure to develop or replace failed 4 kV breakers where ever it may be of a benefit at Fermi 2.

RAI 7 (relating to response to RAI 6.e)

The response indicates that assuming a 15% reduction in main steam isolation valves (MSIVs) failure to close and safety relief valves (SRVs) failure to open has essentially no impact (~<0.01) on risk. On the other hand, operator failures to depressurize have risk reduction worths of 1.10, 1.05, and 1.03. These are equivalent to SRVs failure to open and would indicate that the above reduction in SRV failure to open would lead to a 2% reduction in CDF. Please discuss the MSIV and SRV hardware failure modeling characteristics included in the Fermi 2 PRA that lead to this very small risk impact.

Enclosure

SUBJECT:

REQUESTS FOR ADDITIONAL INFORMATION FOR THE ENVIRONMENTAL REVIEW OF THE FERMI 2 LICENSE RENEWAL APPLICATIONSEVERE ACCIDENT MITIGATION ALTERNATIVES DISTRIBUTION:

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DLR RF E-MAIL:

PUBLIC RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRpb2 Resource RidsNrrDlrRerb Resource RidsNrrDlrRarb Resource RidsNrrDlrRasb Resource RidsNrrDlrRsrg Resource RidsNrrPMFermi Resource DMeléndez-Colón MWentzel YDiaz-Sanabria BWittick BHarris, OGC MKunowski, RIII BKemker, RIII PSmagacz, RIII VMitlyng, RIII PChandrathil, RIII HLogaras, RIII ABarker, RIII