ML021620458
| ML021620458 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/09/2002 |
| From: | Blanch P - No Known Affiliation |
| To: | Anthony Mendiola, Zwolinski J Office of Nuclear Reactor Regulation |
| Sands, S, NRR/DPLM/LPD III-2, 415-3154 | |
| Shared Package | |
| ML021620438 | List: |
| References | |
| Y020020137 | |
| Download: ML021620458 (2) | |
Text
From:
<pmblanch@attbi.com>
To:
<jaz@nrc.gov>, <ajm@nrc.gov>
Date:
5/9/02 11:32AM
Subject:
John/Tony John/Tony On Tuesday this week I listened in on the meeting and believe that the NRC did a great job in making the information available to the general public. For the first time, the phone bridge worked without any significant feedback. Posting the presentation slides on the NRC web site made it very easy to follow the discussions.
I have reviewed the recently issued NRC AIT report and the DB RCA. From these documents and comments made during the meeting I have a few questions. During the meeting it was stated that questions could be submitted via e-mail. Please consider these as formal questions from the meeting and I would appreciate it if you would forward these to the responsible technical person.
- 1. According to the RCA and the AIT, the cracking on nozzle #3 was only axial. If this is true, then why did this nozzle fall over. In order to do this, it had to have circumferential cracking? Am I missing something? I think one of the enclosed photos clearly shows the circumferential crack around the "J" weld.
- 2. If the CRDM had not fallen over, was DB planing to clean the head or, as in the past, restart with a significant boron remaining on the vessel head?
- 3. The AIT and the RCA are consistent in the discussions about circumferential cracking. That is, the circumferential crack initiates from the OD to the ID.
If this is the case, then how is it that circumferential cracking is considered PWSSC? Can I assume that the circumferential cracking is the result of axial cracking?
- 4. During the meeting there were many discussions about axial crack growth rate but I did not hear any discussions about circumferential crack growth rates. It is my assumption that the circumferential cracks present the greater risk from possible rod ejection accidents than the axial cracks.
- 5. Is it possible that a through wall axial crack may occur and remain visually undetected due to a tight interference fit at the top of the head and then cause undetected circumferential cracking during an operating cycle?
- 6. The following statement is made on page #3 of the NRC AIT report: "The cracks in these five nozzles initiated from the outside diameter of the nozzle near the J-groove weld." Again, a crack initiating from the OD does not appear to be PWSCC unless the crack was below the J-groove weld.
Im sure that some of these questions have been answered but remember that I am an Electrical/I&C Engineer.
Paul M. Blanch Pager 800-539-1786 Paul M. Blanch Pager 800-539-1786