ML110420425

Lr - Phone Call to Clarify Seabrook SAMA RAI Responses

ML110420425
Person / Time
Site:	Seabrook
Issue date:	02/11/2011
From:	Office of Nuclear Reactor Regulation
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Download: ML110420425 (5)

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1 SeabrookNPEm Resource From:

Wentzel, Michael Sent:

Friday, February 11, 2011 1:03 PM To:

Cliche, Richard

Subject:

Phone call to clarify Seabrook SAMA RAI responses Attachments:

Final Seabrook SAMA RAI Response Clarifcations.docx

Rick, Below is the call-in information and time for our follow-up phone call to discuss the SAMA RAI responses.

Also, Ive attached the list of clarifications that we would like to discuss on the phone call. If you have any questions or comments, please let me know.

Thanks, Mike Date and time: 2/15 at 2:00pm Phone number: 800-779-9112 Passcode: 37829 MichaelWentzel ProjectManager NRR/DLR/RPB1 (301)4156459 michael.wentzel@nrc.gov

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Phone call to clarify Seabrook SAMA RAI responses Sent Date:

2/11/2011 1:02:49 PM Received Date:

2/11/2011 1:02:48 PM From:

Wentzel, Michael Created By:

Michael.Wentzel@nrc.gov Recipients:

"Cliche, Richard" <Richard.Cliche@fpl.com>

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Clarifications to the RAI Responses Regarding the Analysis of Severe Accident Mitigation Alternatives for the Seabrook Station

1. Response to RAI 1.a. Relative to SAMA #192, provide the change in population dose-risk, and describe NextEras plans for further consideration of this potentially cost-beneficial SAMA. Clarify why the Upper Bound Cost Benefit is only a factor of 1.4, rather than a factor of 1.9, greater than the Nominal Cost Benefit.

2. Response to RAI 1.b.1. Provide the fire and seismic CDF based on the 2006 PRA model used for the SAMA evaluation.

3. The responses to RAI 1.f and 2.e state that Tables F.3.1.1.1-2 and F.3.2.1-2 consider initiating events. However, Tables F.3.1.1.1-2 and F.3.2.1-2 show only basic events, and so it is not clear how initiating events are explicitly considered in the importance analysis. For example, the most dominant initiating event contributor according to the listing in Table F.3.1.1.1-1 is LOSPW, but there appears to be no corresponding event in Tables F.3.1.1.1-2 or F.3.2.1-2. As an example, demonstrate in Tables F.3.1.1.1-2 and F.3.2.1-2 how LOSPW is considered.

4. The responses to RAI 1.f and 2.e also state that Attachment F.A describes a number of SAMA PRA cases that specifically addressed initiating events. While this is the case, it is unclear if all of the dominant initiating events in Table F.3.1.1.1-1 are addressed. For example, while Attachment F.A describes NOLOSP as the modeling case used to determine the benefit of eliminating all Loss of Off-Site Power (LOSP) events, none of the SAMAs evaluated using this case (i.e., SAMA s 13, 14, 16, 24, and 156) specifically addressed initiating event FLLP, Flood in Turbine Building (causing LOSP). Other examples from Attachment F.A are PRA cases FIRE1 and FIRE2, which are the PRA model cases used to determine the benefit of eliminating control room induced LOCA and fire in Turbine Building causing loss of power to emergency buses, respectively.

Neither of these modeling cases addresses the specific scenario of a fire in Switchgear Rooms A or B and no SAMAs were identified or developed to specifically address fire in Switchgear Rooms A and B. In the absence of initiating events in the RRW importance listing, provide a correlation of one or more SAMAs to each of the risk significant initiating events (and a justification for any initiating events not addressed by a SAMA).

5. Response to RAI 1.e. states that the Seabrook Station PRA Group instructions are consistent with requirements of the ASME PRA standard, but neither the ASME standard nor its version is referenced. ER Section F.3.3 states that 2005 focused peer review is against the ASME PRA standard, but again the version is not cited. Identify the version of the ASME standard that applies in these two cases.

6. The response to RAI 2.a. states that Therefore, all Level 1 sequences are evaluated by the CET and it is not necessary to summarize and group similar sequences into Level 1 plant damage states. In light of this response, clarify if the text in the 5th paragraph of ER Section F.3.2.1 about grouping inputs to the Level 2 analysis and the benefits of grouping as a way to focus on the limited number of representative sequences is erroneous or if is there an explanation for this wording.

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7. RAI 2.f response.

i.

Relative to SAMA #193, provide the change in CDF and change in population dose-risk, and describe NextEras plans for further consideration of this potentially cost-beneficial SAMA.

ii.

Relative to basic event #10, page 38 of 116, confirm acronym BE means basic event or provide its meaning if not.

8. Response to RAI 3.b.

i.

Relative to the FIVE fire risk analysis methodology, clarify if fire-induced failures of components or human actions credited for mitigating the initiator are assessed, given that the initiator is now fire-induced (including identifying either new components or actions to be modeled or requantifying the random failure probabilities of previously modeled ones). In addition, clarify if hot shorts are considered and, if so, what probabilities are assigned to these.

ii.

Relative to the Fire-induced ISLOCA & Containment Impact section. For the only area where isolation valves both inside and outside containment could be affected, clarify how important isolation valves [that] could be controlled locally at the valve would be so controlled for valves inside containment during operation. For the letdown system and its several; fail closed AOVs, clarify the basis for the statement it is not credible for all three valves to hot short. For isolation failure of one or more valves of a single train, clarify the statement the ability to remove power from fail closed valves to provide isolation and the case for failed open valves due to hot shorting (which could not be de-powered?).

9. The response to RAI 3.c.a states that However, the present PRA model has been updated to the more recent EPRI hazards and that This was done because, while the methodology and experts used in developing the EPRI hazard are essentially the same as the SSPSA, the EPRl hazard is more recent and the EPRl uniform hazard spectrum (UHS) developed for the Seabrook Station site is more realistic than that used in the SSPSA. Since the EPRI hazard curve was assessed in the IPEEE as a sensitivity case, clarify what has changed to conclude that the EPRI hazard curve is more realistic than the SSPSA hazard curve.

10. RAI 3.g response. A seismic CDF of 2.2E-05 per year, based on the updated 2008 USGS seismic hazard curves (as determined from GI-199 information), was used to develop a factor of 2.6 multiplier on the MAB. The revised MAB was used to re-assess only those Phase II SAMAs that were qualitatively screened based on high cost or low benefit. Phase II SAMAs that were quantitatively evaluated and determined to not be cost-beneficial in the original analysis were not re-assessed in the RAI response. Based on a scoping assessment by the NRC staff, applying the 2.6 multiplier to the estimated benefit for these non-re-assessed SAMAs will result in many SAMAs becoming potentially cost-beneficial, based on the current cost estimates. Provide an assessment of the impact of the higher seismic CDF on all SAMAs, including those identified and evaluated in response to RAIs.

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11. The response to RAI 5.b states that all top ranked basic events related to LERF have been addressed in response to RAI 2.f. This appears to be the case with the exception of basic event FWP161.FS, which has a LERF RRW of 1.0886 (see ER Table F.3.2.1-2).

Provide an assessment of this basic event for SAMAs.

12. The response to RAI 5.b provides the same disposition (not beneficial based on eliminating all SEPS failures), same associated SAMAs (#9 and #14), and same two pairs of case studies (PRA cases SEPES for #s 8-9 and OSEP1 for #s 10-11) for basic events #8, #9, #10, and #11, yet the estimated benefits are different between the pairs

1. s 8-9 and #s 10-11. Clarify the differences in the treatment of these four SAMAs, including the two different case studies.

13. In the response to RAI 5.f for Essential Switchgear Rooms, clarify if electrical raceway fire barriers also considered for areas where cables for redundant trains may be co-located.

14. The results of a Phase II evaluation of SAMA 79 are provided in response to RAI 5.g.

Provide the change in CDF and change in population dose-risk for this SAMA (Case FW01, while as described in ER Appendix F.A, does not appear to have been used for any other SAMA).

15. RAI 5.n response. Provide the change in CDF and change in population dose-risk for SAMA 105 (PRA Case OLPRS).

16. RAI 6.a response. The OECR reduction is shown to be 9% for SAMAs 96, 108, and 109, yet the benefit at both 7% discount rate and for the Upper Bound are reported in the ER to be <$1K. Clarify the basis for the <$1K benefit given the 9% reduction in OECR.

17. RAI 6.k response. Clarify why NextEra believes the uncertainty distribution adequately represents the uncertainty in the fire and seismic portions of the PRA model. Include a discussion of whether probability distributions were assigned for external events (such as for fire ignition frequencies, non-suppression probabilities, hot short probabilities, seismic frequencies, other seismic parameters) and, if not, how this incompleteness impacts the SAMA analysis.