ML20009H192
| ML20009H192 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 07/30/1981 |
| From: | Van Vliet J Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8108070012 | |
| Download: ML20009H192 (2) | |
Text
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> MEMORANDUM FOR: Darrell G. Eisenhut, Director f". vision of Licensing D
A FRON:'
James A. Van Vliet, Project Manager
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Operating Reactors Branch #2, DL g
THRU:
Thomas A. Ippolito, Chief g
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05 N N9 Operating Rdactors Branch #2, DL
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SUBJECT:
BRUNSWICK 1 AND 2 MSIV FAILURES b
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PURPOSE By blus ticket #40'you requested a meeting by July 31, 1981 to discuss the MSIV failure problem at Brunswick. This memorandum:
(1) provides the background and present status of that problem; and, (2) suggests that the meeting yourrequested be deferred pending completion of IE and NRR (MEB) evaluations.
BACKGROUND The Brunswick MS'IVs were built by Rockwell Manufacturing.
In addition to Brunswick 1 and 2, these valves are installed in five domestic operating plants, seven foreign operating plants, and eight requisition plants. Seven failures of the type in question have been identified.
Five of these failures have occurred at Brunswick 2, one at Brunswick 1, and one at Hatch 2.
The July 18 failure was the third one to occur at Brunswick this year.
Two failure modes exist. The first mode is separation of the stem disc from the stem.
(See attached figure.) Since the stem disc supports the ueight of the main disc, the stam disc tosstem separation results in ntain disc closure.
The second failure mode is separation of the main disc from the main disc pisten, also resulting in main disc closure.
Prior to the July 118 failure, the licensee's attunpted solution to this problem has been to increase the number of pins at the mating surfaces. This has not proven successful.
Folbwing the July 18 failure, an IE inspection team visited Brunswick and determined three probable reasons why these failures occur at Brunswick and i
essentially nowhere else. There reasons are:
- 1) Hain strmm piping runs are such that 900 elbows are located immediately up5tream f the MsIvs.
In addition, 300 elbows are located next to the 90 90 elbows on two of the four steam lines. The turbulance caused by these f
pipipg aenas may resui 6 in sign 1 Ticanc viurat ion oT ma wa pu n en u.
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- 2) Poor maintenance practices and incomplete maintenance procedures may be a major contributor to this problem. As an example, past MSIV inspections have suggested that the stem disc to item and main disc pins may not have been reinstalled on some MSIVs following disassembly.
- 3) Incomplete thread engagement was discovered on the stem disc to stem connection and the main disc to piston connection.
(This could be indicative of a manufacturer's QA program deficiency and will be-investigated during an IE plant vistt in August.)
STATUS The licensee, in conjunction with Rockwell, has effected a temporary fix for the two failed valves on Unit 2, and IE has permitted continued operation based on acceptance of a licensee safety evaluation. The licensee also plans to inspect / repair Unit 1 MSIVs during the present outage.
For the long-term solution, they have contracted with Wylie Labs to work with Rockwell in finding the true cause and perrranent solution for tFis problem.
are interested in a quick resolution.
They The IE and MEB evaluations thould be completed within the next thirty days.
At that time we will be in a better position to determine what. if any, additional action is warranted.
I will keep you advised of developr.ents on this matter.
/S/
James A. Van Vliet, Project Manager Operating Reactors Branch #2 Division of Licensing Attachment As stated DISTRIBUTION:
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