ML031110106

E-mail from W. Cullen to C. Fairbanks, Regarding Draft Sow for Davis Besse Crack

ML031110106
Person / Time
Site:	Davis Besse
Issue date:	09/12/2002
From:	Cullen W Office of Nuclear Regulatory Research
To:	Nilesh Chokshi, Carolyn Fairbanks, Hixon J, Diane Jackson, Matthew Kirk, Shah Malik, Cayetano Santos, Robert Tregoning Office of Nuclear Regulatory Research
References
FOIA/PA-2003-0018
Download: ML031110106 (1)

Text

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.VGtVit"V,,,,o,_ , ,,,,, ,.e.R-^" . .. a From: William Cullen / I5 To: Carolyn Fairbanks; Cayetano Santos; Deborah Jackson; Jeffrey Hixon; Mark Kirk; Nilesh Chokshi; Robert Tregoning; Shah Malik Date: 9/12/02 4:56PM

Subject:

Re: Draft SOW for Davis Besse Crack I just finished reading the document about the defects in six-wire clad that Mike got from Merschoff (?).

While reading, I realized a couple of things I had not thought about earlier.

(1) Residual stresses at the clad/LAS interface. When the clad solidifies at the interface first, I think I remember that the LAS is put into compression, and the clad is put into tension. So when the LAS corrodes away, and the compressive stresses disappear with it, the clad on the interface side is going to be left in tension, giving a lot of stress favoring initiation of cracks. This stress is probably independent of orientation.

(2) The report describes interdendritic cracking at the surface, with slag (presumably flux) inclusions.

While the chances of having flux entrapment all the way down at the interface are really, really minimal, I do suppose that the interdendritic grain boundaries are still the weak link in the system.

(3) The report speaks of archived nozzle dropouts (this was a nuclear Navy vessel). I don't think the nuclear Navy ever throws anything out of its closet, and it may be possible that we could get our hands on some six wire clad from the early 70's era by working with the right people. I know that working with the nuclear Navy is a PITA, but it might be worth a try, in this case.

BC William H. Cullen, Jr., Sr. Materials Engineer Materials Engineering Branch Office of Nuclear Regulatory Research (for mailing, abbreviate as "RES/DET/MEB")

US Nuclear Regulatory Commission Mail Stop: T-10 El0 Washington, DC 20555 Ph: 301 - 415 - 6754 FAX: 301 - 415 - 5151 whc @nrc.gov

>>> Cayetano Santos 09/12/02 04:39PM >>>

Attached is draft SOW we put together today to try to address the cracking found in the cladding of Davis Besse.