ML19290B946
| ML19290B946 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 12/07/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R Maine Yankee |
| References | |
| NUDOCS 7912190753 | |
| Download: ML19290B946 (1) | |
Text
%
neauq'o, UNITED STATES
[
g NUCLEAR REGULATORY COMMISSION g
c REGION I O,
[
631 PARK AVENUE
%,**O* * *,o#
KING OF PRUSSIA, PENNSYLVANIA 19406 Docket No. 50-309 DEC 0 71979 Maine Yankee Atomic Power Company ATTN:
Mr. Robert H. Grace Licensing Engineer 20 Turnpike Road Westborough, Massachusetts 01581 Gentlemen:
The enclosed IE Bulletin No. 79-28, is forwarded for action. A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, A
Boyce H. Grier Director
Enclosures:
1.
List of Recently Issued IE Bulletins CONTACT:
S. D. Ebneter (215-337-5296) cc w/encls:
E. Wood, Plant Superintendent E. W. Thurlow, President 1731 285 7912190
ENCLOSURE 1 UNITED STATES SSINS No.: 6820 NUCLEAR REGULATORY COMMISSION Accession No.:
OFFICE OF INSPECTION AND ENFORCEMENT 7910250505 WASHINGTON, D.C.
20555 IE Bulletin No. 79-28 Date: December 7, 1979 Page 1 of 2 POSSIBLE MALFUNCTION OF NAMCO MODEL EA180 LIMIT SWITCHES AT ELEVATED TEMPERATURES Description of Circumstances:
The NRC has been recently advised through a 10 CFR 21 report from NAMC0 Controls that a malfunction of a NAMC0 Model EA180 stem nounted limit switch (SMLS) occurred at the Cooper Nuclear Station.
Investigation into the switch failure by the licensee revealed yellow and brown " crystal-like" resin deposits on the internal components of the switch. The affected switch is located inside the drywell containmeu at this facility and was being used as the replacement switch for an unqualified SMLS previously identified in IE Bulletin Nos. 78-04 and 79-01.
According to the manufacturer, the problem was traced to a batch of top cover gaskets of which some were over-impregnated and insufficiently heat cured.
It has been determined that this condition can leave an uncured residue of " Loctite" in the gasket, which vaporizes at sustained temperatures above 175 F.
To correct the problem, the manufacturer has revised production techniques beginning Septemuer 1979 in order to better control the impregnation process and to properly heat cure the gaskets following impregnation.
This problem is unique to all NAMC0 Model EA180 series switches received by licensees after March 1, 1979.
According to the manufacturer, the suspect switches can be identified by checking the date code which is a 4 digit number stamped on the conduit boss of the switch housing. NAMCO recommends that any EA180 series switch with a date code between 02-79 through 08-79 should have its top cover gasket replaced.
Also, licensees should request from their suppliers of equipment on which NAMCO EA180 series switches are used that they check their inventory cnd replace top cover gaskets on switches date coded between 02-79 through 08-79.
The enclosed letter from NAMC0 further describes the high-temperature environ-mental problem with the top cover gaskets used in their EA180 switches and provides recommendations to correct the problem. According to NAMCO, this letter has been sent to each customer who was shipped EA180 switches between February 21, 1979, and August 24, 1979.
Action to be Taken by Licensees of P Holders of Construction Permits:
DUPLICATE DOCUMENT Entire document previously entered into system under:
7 7/6 M 6 5
$~
1731 286 aNO h
No. of pages: