ML19208B659
| ML19208B659 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 09/10/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 7909210144 | |
| Download: ML19208B659 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION Eh o
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011 RYAN PLAZA DRIVE, SUITE 1000
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,o AR LINGToN, TE XAS 76012 September 10, 1979 Docket No.
50-298 Nebraska Public Power District ATTN:
J. M. Pilant, Director Licensing & Quality Assurance Post Office Box 499 Columbus, Nebraska 686C1 Gentlemen:
The enclosed IE Circular No. 79-18 is forwarded to you for information.
No written response is required. Should you have any questions related to your understanding of the recommendations on this matter, please contact this office.
Sincerely, 7
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Karl V. Seyfri Director
Enclosures:
1.
IE Circular No. 79-18 2.
List of IE Circulars Issued in Last Six Months cc:
L. C. Lessor, Superintendent Cooper Nuclear Station Post Office Box 98 Brownville, Nebraska 68321
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 79-18 Date:
September 10, 1979 Page 1 of 2 PROPER INSTALLATION OF TARGET ROCK SAFETY-RELIEF VALVES Description of Circumstances:
As a result of NRC monitoring of operating experiences involving the Target Rock safety-relief valve, two potential problems have been identified. One potential problem ic that the performance of the valve has been found to be impaired by either execssive or insufficient insulation around the valve body when installed in its service environment. The other potential problem is that improper assembly of the modified valve can result in inoperability.of the remote air actuator.
The Target Rock safety-relief valve is a dual purpose valve in that overpressure response is provided by pilot valve action and automatic depressurization (ADS) is provided by a remote air actuator. Valve operation has been found to be affected by the amount of insulation placed around the valve body. A previous IE Bulletin No. 76-06 was issued on July 21, 1976, as a result of operating experiences where excessive insulation was installed on the valve.
The excessive insulation caused excessive heat to be retained producing a higher temperature environment for the elastomeric diaphragm which resulted in accelerated deterioration of the elastomer. Failure of the elastomeric diaphragm makes the valve inoperable in the power-operation mode (i.e., manual and ADS).
Subsequently, a silicone-nomex diaphragm was developed by the manufacturer to provide a longer life in high temperature environments.
In addition, the IE Bulletin explicitly required that insulation be installed in accordance with the manufacturer's recommendations.
A recent licensee event report from the Monticello facility identified a potential problem resulting from insufficient insulation (i.e., just opposite of the condition addressed by IE Bulletin 76-06). During the performance of special testing of the response to safety-relief valve operation, a valve was discovered to be exceeding its design delay time for opening. Subsequent inspection and testing of the valve revealed that insufficient insulation may cause condensation to accumulate in the pressure venting ports which then results in delaying the opening of the main disk. This slower response time is significant with respect to primary system overpressure and similar transient response analyses. Although the reported three-stage Target Rock safety-relief "al of insulation are similarly applicable tc DUPLICATE DOCUMENT
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