ML17283A084

NRR E-mail Capture - (External_Sender) Seabrook Flooding MSA & FE Question

ML17283A084
Person / Time
Site:	Seabrook
Issue date:	10/04/2017
From:	Thomas C NextEra Energy Seabrook
To:	Frankie Vega Division of Licensing Projects
References
Download: ML17283A084 (2)

Text

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

Sent: Wednesday, October 04, 2017 3:57 PM To: Vega, Frankie Cc: Axelson, Karl; Browne, Kenneth

Subject:

[External_Sender] Seabrook Flooding MSA & FE Question Good afternoon Frankie, As requested, here is a summary of our phone conversation from this afternoon:

Seabrook recently submitted the Flooding Hazard Reevaluation Report (FHRR) to evaluate the impact of a beyond design basis external events (BDBEE) on-site. The FHRR has been accepted by the NRC as the basis to determine the effects of a BDBEE on Seabrook Station.

Detailed topographic data was used in the FHRR supporting calculations to develop site-specific flooding models. The FHRR was then used as design input into the Mitigating Strategies Assessment (MSA) and Focused Evaluation (FE) to determine the impact of BDBEE flooding on the FLEX Program and critical plant SSCs. The NRC is currently reviewing the MSA and FE to verify that Seabrook Station will be adequately protected against these flooding hazards.

The site-specific flooding models developed for the FHRR use detailed survey data. NextEra Energy Seabrook is looking to pave some areas inside the protected area which would alter the elevations due to the high level of detail in the survey data and the inaccurate nature of the hot-topping process. NEE has run a paving sensitivity case to capture the worst case scenario effects of the proposed paving project. The paving sensitivity case added two inches to the existing elevations at the proposed paving locations, and recalculated flood depths on-site. The results of this model run were then plugged into the MSA and FE Engineering Evaluations. The conclusion was that an additional 2,089 gallons of flood water would enter the Unit 2 Tunnel and Waste Process Building reducing flooding margin by 10%. The intent is to remove the existing paving and repave to approximately the same contour, but the "paving sensitivity case would bound any elevation changes and provide margin for error.

As discussed, 50.54F responses are a snap-shot in time. We understand that the documents like the MSA are part of our licensing basis and need to be maintained as such. The specific question for you is, considering that the MSA and FE are currently under review by the NRC, do you require any notification or discussion of the changes to the model?

Ill be out of the office starting Friday through Monday, October 16th. Please feel free to contact the Project Manager, Karl Axelson (603-773-7745) or the Licensing Manager, Ken Browne (603-773-7932) in my absence, especially if you feel a phone call is warranted.

Thank you, Christine 1

Hearing Identifier: NRR_PMDA Email Number: 3762 Mail Envelope Properties (5539b7ad182a47b69fff2ea7c4150400)

Subject:

[External_Sender] Seabrook Flooding MSA & FE Question Sent Date: 10/4/2017 3:56:48 PM Received Date: 10/4/2017 3:56:56 PM From: Thomas, Christine Created By: Christine.Thomas@nexteraenergy.com Recipients:

"Axelson, Karl" <Karl.Axelson@nexteraenergy.com>

Tracking Status: None "Browne, Kenneth" <Kenneth.J.Browne@nexteraenergy.com>

Tracking Status: None "Vega, Frankie" <Frankie.Vega@nrc.gov>

Tracking Status: None Post Office: nexteraenergy.com Files Size Date & Time MESSAGE 2467 10/4/2017 3:56:56 PM Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received: