March 14th, 2011 – What a licensee needs to determine to ensure not exceeding licensed limits

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From: Case, Michael
Sent: Wednesday, March 16, 2011 8:11 AM
To: Murphy, Andrew –
Cc: Kammerer, Annie; Ake, Jon; Hogan, Rosemary; Richards, Stuart; Uhle, Jennifer
Subject: FW: Seismic and Tsunami Hazard in PRA

Hi Andy. Can you take the lead for this one in coordination with Annie and Jon? I sort of see an overview of where the agency is seismically and tsunamically (new word!) and how we approach various issues (including PRA). I’d shoot for about a half hour presentation and a half hour for discussion with all the folks Jennifer indicated.

Shoot for early to mid next week?

From: Uhle, Jennifer
Sent: Monday, March 14, 2011 5:09 PM
To: Coe, Doug; Sheron, Brian; Coyne, Kevin; Case, Michael
Cc: Stutzke, Martin; Sancaktar, Selim
Subject: RE: Seismic and Tsunami Hazard in PRA

Thanks. I am going to ask DE to put together an update on where we are with understanding tsunami hazard due to either seismic or landslide and all on this email should attend. Annie has the lead for tsunami and John Ake has it for GI-1 99. So, Mike Case, yours, right…

From: Coe, Doug
Sent: Monday, March 14, 2011 4:59 PM
To: Sheron, Brian; Uhle, Jennifer; Coyne, Kevin; Case, Michael
Cc: Stutzke, Martin; Sancaktar, Selim.
Subject: RE: Seismic and Tsunami Hazard in PRA

Hi all,

My BB doesn’t work here, but webmail does, so I’m following the discussions sporadically. GI-199 is based on recent ‘best’ understanding of seismology throughout the US. The information needed to understand plant-specific risk, last time I discussed with NRR, is expected to be collected from all US licensees, including those on the West Coast.

However, GI-199 doesn’t specifically address related tsunami impacts, but it probably should fbr all coastal or nearcoastal plants. The generic communciation is still being written by NRR with our support, so there is an opportunity to discuss this with NRR, and with DE. Clearly there will be a lot more attention on GI-199.

Jennifer’s restart basis question is a good one. In practice a licensee needs to determine from engineering analysis that the stresses on the plant did not exceed their licensed limits. That would be a very tall order for a plant that experienced a beyond design basis quake, and probably is why it had taken Japan so long to restore the KK plants following the earlier quake.

Doug

From: Sheron, Brian
Sent: Monday, March 14, 2011 3:27 PM
To: Uhle, Jennifer; Coyne, Kevin; Case, Michael
Cc: Coe, Doug; Stutzke, Martin; Sancaktar, Selim
Subject: RE: Seismic and Tsunami Hazard in PRA

The question is, did the Japanese also consider an 8.9 magnitude earthquake and resulting tsunami “way too low a probability for consideration”?

Look at GI-1 99. It shows we didn’t know everything about the seismicity of CEUS. And isn’t there a prediction that a the West coast is likely to get hit with some huge earthquake in the next 30 years or so? Yet we relicense their plants ………..

From: Uhle, Jennifer
Sent: Monday, March 14, 2011 3:20 PM
To: Sheron, Brian; Coyne, Kevin; Case, Michael
Cc: Coe, Doug; Stutzke, Martin; Sancaktar, Selim
Subject: RE: Seismic and Tsunami Hazard in PRA

I think this highlights our need to get a better handle on external events hazards-ensure that the tsunami hazard is way too low a probability for consideration.

I know we are updating our tsunami hazard for the east coast and gulf coast but did not think we were doing recent work on the west coast.

Has industry done anything on tsunami hazards?

Also, has anyone done work to look at the effect of numerous cycles of low amplitude acceleration following a larger event.

I would expect we would have some information because how do we-know a plant would be fit to start back up after an event?

We cannot possibly do NDE on everything to determine if flaws have propagated to the point where they need to be replaced.

From: Sheron, Brian

Sent: Monday, March 14, 2011 3:05 PM
To: Coyne, Kevin
Cc: Uhle, Jennifer; Coe, Doug; Stutzke, Martin; Sancaktar, Selim
Subject: RE: Seismic and Tsunami Hazard in PRA

And so the first question is, “Should we make licensees consider a Tsunami coincident with a seismic event that triggers the Tsunami?”

The second question is, How should we consider after-shocks in seismic hazard analyses?

From: Coyne, Kevin
Sent: Monday, March 14, 2011 2:39 PM
To: Sheron, Brian
Cc: Uhle, Jennifer; Coe, Doug; Stutzke, Martin; Sancaktar, Selim
Subject: Seismic and Tsunami Hazard in PRA

Brian –

You raised a question at the standup meeting this morning regarding (1) the treatment of coupled seismic and tsunami events and (2) treatment of seismic aftershocks. I spoke with Marty Stutzke and Selim Sancaktar – the PRA Standard (ASME/ANS-Ra-Sa2009) does address the technical requirements for both seismic events and tsunamis (tsunami hazard under the technical requirements for external flooding analysis).

The standard does note that uncertainties associated with probabilistic analysis of tsunami hazard frequency are large and that an engineering analysis can usually be used to screen out tsunamis.

Seismic PRAs do not consider the affect of aftershocks since there are not methods to predict equipment fragility after the first main shock.

Although the standard does address both these events, there are not specific requirements that require a PRA to assess a tsunami generated by a local seismic event.

Marty also checked on the Diablo Canyon and San Onofre IPEEEs – based on the Technical Evaluation Reports, Diablo did consider a locally induced tsunami in a limited way (the aux service water pumps were assumed to become flooded following a seismic event) while SONGS did not consider a coupled seismic/tsunami event.

-Kevin

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