ML19211C102
| ML19211C102 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/07/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| IEB-79-28, NUDOCS 8001100080 | |
| Download: ML19211C102 (1) | |
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tiSIC December 7, 1979 Docket Nos. 50-368 50-313 k; kansas Power and Light Company ATTN:
Mr. William Cavanaugh III Vice President of Generation and Construction Post Office Box 551 Little Rock, Arkansas 72203 Gentlenen:
Enclosed is IE Bulletin No. 79-28 which requires action by you with regard to your power reactor facilities with an operating license or a construction permit.
Should you have questions regarding this Bulletin or the actions required of you, please contact this office.
Sincerely, 4
Karl V. Seyfr Director
Enclosures:
1.
List of Recently Issued IE Bulletins cc:
James P. O'Hanlon, Plant Manager Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72801 1737 206
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 NAMCO Controls that a malfunction of a NAMCO Model EA180 stem mounted 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 containment 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 September 1979 in order to better control the impregnation process and to properly heat cure the gaskets following impregnation.
This problem is unique to all NAMCO 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 and replace top cover gaskets on switches date coded between 02-79 through 08-79.
The enclosed letter from NAMCO 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 'ugust 24, 1979.
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