ML19290C143
| ML19290C143 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 12/07/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8001100130 | |
| Download: ML19290C143 (1) | |
Text
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UNITED STATES CENTRAL FILES fa arcoq'o, NUCLEAR REGULATORY COMMISSION PDR:HQ
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December 7, 1979 Jocket No. 50-267 Public Service Co=pany of Colorado ATTN:
Mr. C. K. Millen Senior Vice President Post Office Box 840 Denver, Colorado 80201 Gentlemen:
Enclosed is IE Bulletin No. 79-28 which requires action by you with regard to your power reactor facility 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, KarlV.Seyfrit,[
Director
Enclosures:
1.
List of Recently Issued IE Bulletins cc:
D. W. Waremoourg, Nuclear Product on Manager Fort St. Vrain Nuclear Production P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance 8001100
UNITED STATES SSINS No.: 6820 NUCLEAR REGULATORY COMMISSI0f Accession No.:
OFFICE OF INSPECTION AND ENFORCEh_dT 7910250 ((
WASHINGTON, D.C.
20555 IE Bulletin No. 79-28 Date:
December 7, 1979 Page 1 of 2 POSSIBLE MALFUNCTION OF NAMCO MODEL EA180 LIMT"' 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 manuf..cturer, 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 t..e 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.
7 7 gjq Action to be Taken by Licensees of.....
Holders of Construction Permits:
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Determine if your facility has i Entire document previously switches in any safety-related e entered nto system under:
containment, including valve pos containment isolation valves.
ANO No. of pages:
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