ML17256A775

[External_Sender] Seabrook Flooding MSA

ML17256A775
Person / Time
Site:	Seabrook
Issue date:	09/11/2017
From:	Thomas C NextEra Energy Seabrook
To:	Vega F G Japan Lessons-Learned Division
References
Download: ML17256A775 (3)

Text

1 NRR-PMDAPEm Resource From:Thomas, Christine <Christine.Thomas@nexteraenergy.com>

Sent: Monday, September 11, 2017 8:40 AM To: Vega, Frankie

Subject:

[External_Sender] RE: Seabrook MSAGood morning Frankie, Please see responses in red.

Regards, Christine

From: Vega, Frankie [mailto:Frankie.Vega@nrc.gov

] Sent: Tuesday, August 29, 2017 2:45 PM To: Thomas, Christine

Subject:

Seabrook MSA CAUTION - EXTERNAL EMAIL Hello Mrs. Thomas; The technical staff is currently reviewing Seabrook's MSA and has identified few areas in which clarifications are needed in order to complete the review. Since these are relatively simple clarifications, no formal responses are needed at this moment so replying to this email would work for the staff.

• Flood Event Duration o Between MSA Tables 3-1 and 3-2 the licensee uses the terms "Period of Inundation" for storm surge, and "Duration of Significant Flooding" for LIP. It is not clear if these terms are intended to be different or synonymous. Please clarify if these descriptions represent the same duration parameters for both hazards. Note that "Period of Inundation" is the term utilized and described

in NEI 16-05.

Response: There is no intended significant difference. In the case of LIP, the term "Duration of Significant Flooding" was intended to convey the fact that the durations from the FHRR are for time above door thresholds or floor levels as opposed to a duration of any flooding or ponding on site.

• Associated Effects o Based on the description of Associated Effects parameters throughout the MSA submittal, particularly in Tables 3-1 for LIP, and 3-2 for PMSS, with associated notes, the licensee considers several types of debris, particularly in the footnotes. However, each of the debris categories (e.g. wind generated debris, waterborne debris, and sediment debris, etc.) are not consistently addressed and supported between the evaluated hazards. Please list and explain the various types of debris considered for LIP and PMSS flood hazards.

Response: Debris referred to in Tables 3-1 (LIP) and 3-2 (PMSS), other than Note 6 in both tables, concerns waterborne debris only. With regard to the difference in the description of Associated Effect #3 from Table 3-1 to Table 3-2, there is no technical reason for the difference. The term debris was removed in Table 3-2 Associated Effect #3 to be consistent with the 2referenced Table 3-2 Note 3, which refers to hydrostatic and hydrodynamic loading. In Table 3-2, sediment and debris loading (which are essentially synonymous in this context) and waterborne projectiles are discussed in Associated Effect #4 and #5 and Notes 4 and 5 respectively. The MSA would have been more consistent if a similar change was made in Table 3-1. The statement in the executive summary "PMSS flooding delays access to the site for debris removal and deployment of portable equipment" is only intended to reflect the overall impact of the storm surge with regard to implementation of FLEX strategies. Debris removal in this context is for wind generated debris; removal of which is considered by our FLEX Program. It is not intended to include waterborne debris, consistent in that regard with the later statements that such debris is not a concern for the Seabrook site. This is true for Note 6 in Table 3-1 and 3-2 as well. The note is intended to address the Associated Effect of potential concurrent high wind conditions and to reflect that the FLEX Program considers removal of wind generated debris.

The debris referred to in Note 6 is wind generated, not waterborne.

o MSA Table 3-2 indicate that sedimentation was not considered significant (bounded). Please clarify on how the sediment load coming from offsite as part of the PMSS analysis was estimated, given Note 4 in Table 3-2, and the discussion of drainage area. Response: Sedimentation is not a concern for the PMSS event. During the PMSS, there is no standing water on site. However, water does enter the site from overtopping waves. It is assumed that sediment will be mobilized and transported in Hampton Harbor during the hurricane event, both as bedload transport near the bottom and suspended particles above the bedload movement. However, near the surface, the water column will be relatively sediment free Therefore, minimal sediment will be carried onto the site (in the PA) by the overtopping waves at the peak of the event. The overtopped water will then flow around the site's mostly paved surfaces, so there is little opportunity to mobilize any other sediments.

If you have questions or need clarification on the questions above, please let me know. Also, please provide an estimated response date.

Thanks

Frankie G. Vega, P.E. Project Manager NRR/JLD/JHMB 301-415-1617 Location: O-13H12

Hearing Identifier: NRR_PMDA Email Number: 3724 Mail Envelope Properties (68856126dfe04fb7a690723b70a61b36)

Subject:

[External_Sender] RE: Seabrook MSA Sent Date: 9/11/2017 8:39:53 AM Received Date: 9/11/2017 8:40:04 AM From: Thomas, Christine Created By: Christine.Thomas@nexteraenergy.com Recipients: "Vega, Frankie" <Frankie.Vega@nrc.gov>

Tracking Status: None

Post Office: nexteraenergy.com Files Size Date & Time MESSAGE 4611 9/11/2017 8:40:04 AM

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