ML19208B684
| ML19208B684 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 09/10/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 7909210187 | |
| Download: ML19208B684 (1) | |
Text
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UNITED STATES
,[o dV'5 NUCLEAR REGULATORY COMMISSION o
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0, 101 MARIETTA ST N.W SUITE 3100
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- o ATLANTA.G EORGIA 30303 SEP 101979 In Reply Refer To:
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50-395 South Carolina Electric and Gas Company Attn:
T. C. Nichols, Jr., Vice President Power Production and System Operations Post Office Box 764 Columbia, South Carolina 29218 Gentlemea:
The enclosed Circular No. 79-18 is forwarded to you for information.
No i
written response is required. Should you have any questions related to your understanding of the recommendations on this matter, please contact this office.
Sincerely, y- -
A James P. O'Re111 Director
Enclosures:
1.
IE Circular No. 79-18 2.
List of IE Circulars issued in the last six months
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3 Accession No: 79082003E5 SSINS No. 6830 s
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
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September 10, 1979 IE Circular No. 79-18 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 is that the performance of the valve has been found to be impaired by either excessive 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 remota 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 deprescurization (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 tempe~rature 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). Daring 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 event at Monticello involved the three-stage Target Rock safety-relief valves, the requirements for proper amounts of insulation are similarly applicable valves.
DUPLICATE DOCUMENT c,* C;pb, The second potential problem was recen The licensee event report indicated th-Entire document previously entered design two-stage valve resulted in pre into system under:
ANO M OS7.003S6 No. of pages:
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