ML19208B675
| ML19208B675 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/10/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7909210170 | |
| Download: ML19208B675 (1) | |
Text
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o UNITED STATES l'
- At NUCLEAR REGULATORY COMMISSION 5.
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8 1990 N. CALIFORNI A BOULEVARD d
SUITE 202, WALNL?T CREEK PLA7A
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WALNUT CREEK, CALIFORNIA 94536 September 10, 1979 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
The enclosed 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, bdl mens ~
R. H. Engelken Director
Enclosure:
IE Circular No. 79-18 cc w/ enclosure:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD bob $.i.Nl g gg '4 )
Accession flo: 7908200385 SSIflS fio. 6830 UNITED STATES NUCLEA'l REGULATORY C0!?11SSION OFFICE OF INSPECTION AND ENFORCEf1EflT WASHINGTON, D.C.
20555 September 10, 1979 IE Circular No. 79-18 PROPER INSTALLATION OF TARGET ROCK SAFETY-RELIEF VALVES Description of Circumstarices:
As a result of flRC 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 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 renote air actuator. Valve operation has been found to be effected 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 elastoneric diaphragm, makes the valve inoperable in the power-operation mode (i.e. manual and ADS).
Subsequently, a silicone-nomex diaphragn was developed by the manufacturer to provide a longer life in high temperature environnents.
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 flonticello 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 response analyses. Although the report three-stage Target Rock safety-relief v% DUPLICATE DOCUMENT 4' s f "S13' G
ry of insulation are similarly applicable J Entire document previously entered valves-into system under:
e The second potential problem was recentlh ANo W6MdO36 The licensee event report indicated thatt design two-stage valve resulted in preve No. of pages:
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