ML031040276

E-Mail from Mark Kirk to Steven Long Re Probabilistic Calculations for Davis-Besse

ML031040276
Person / Time
Site:	Davis Besse
Issue date:	05/31/2002
From:	Matthew Kirk Office of Nuclear Regulatory Research
To:	Long S Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0018
Download: ML031040276 (2)

Text

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From: Mark Kirk, ZLZ; To: Steven Long Date: 5/31/02 9:10AM

Subject:

Re: Probabilistic Calcs for DB Steve -

Kindly e-mail me Dale's input when available. Also e-mail to Richard Bass at ORNL (ust to make sure that he get's it quickly too). Richard is at bassbr~oml.sov Thanks Mark

>>> Steven Long 05/30/02 07:53AM >>>

ale Wuokko of Davis-Besse says he will provide the latest geometry of the cavity today.

We will have to proceed on the basis of that information, because better Information will not be avialable fL) 4y on a timely basis. We need to produce a technical basis sufficient to support a preliminary significance determination as soon as possible. Refinements of our technical assessments can be done if warranted when 'all of the information Is In.

Steve

>>> Mark Kirk 05/29/02 04:05PM >>>

(-8Eteve -

Following the conversations many of us have had over the past few weeks, i would suggest the following course of action:

1. ORNL will further refine their mesh in the cladding, and perform more detailed analysis of the results of these runs. After talking with Richard (Bass) it is his view that becasue the maximum pressure at which you are Interested in probabilities is fairly lw (2500 psi), the differences in failure criteria that we believe In (here 'we' is NRC RES and our contractors) may be fairly small. An examination of these FE results will help us to make this determination. This of course will not tell us what the 'right" failure criteria is (seeking absolute truth Inthis matter may take far more time than we have) but it will help us to better assess the uncertainty Inresults that arises due to our uncertainty about what the rightu criteria is.

/,4 2. As we have discussed before, it iscritically Important in our final calculations (not the #1 calcs - but the

1. 3 calcs) to have a much less equivocal definition of the geometry of both the cavity and the cladding than we have now (i have not yet seen what the licensee olast* sent ... but I don't think it Iswhat we are looking for). I we cannot get a better geometric definition then geometry will have to be a parameter that varies In the probabilistic analysis, and that will significantiy complicate the effort. Since the combination of the cavity geometry and the cladding geometry has a first order effect on the results - and since it is something that is In principal knowable - we feel strongly that this is Information we should press the licensee to provide ... or we should obtain ourself. I we do the probabilistic analysis and retain geometry as a variable we will only further blur the results ... and therefore further Impede your ability to draw clear conclusions from it.

3. Once we have insights from #1 and the Info from #2 we will perform the appropriate 3D FEA at ORNL to define the fragility curves. Random variables Inthis analysis will be (definitiely) the stress-strain properties and (maybe - but hopefully not) the cladding thickness.

Inview of the urgency here I am asking Richard and Paul (by this e-mail) to begin with the analyses lrfor.

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~irkirk- _ Re

_- ~Page 2 outlned In #1above. However, as we have previously discussed, funding considerations still need to be worked out between your boss and my boss. Accordingly, unless directed to do so by Nilesh Iwill not have Richard and Paul continue with this analysis past Monday (hopefully Nilesh can work out something appropriate with you guys by then).

Also, Ihave to be away from the office for the next two days for personal reasons. I will, however, be checking e-mail from at least Thuray evening and Friday mid-day or evening). If you need to contact me there I ap Mark Mark CC: Bass, Richard - ORNL; Deborah Jackson; Edwin Hackett; Mark Kirk; Nilesh Chokshi; Paul Williams; Wallace Norris J0