ML19208B670
| ML19208B670 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 09/10/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7909210162 | |
| Download: ML19208B670 (1) | |
Text
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UNITED STATES E '"
'n NUCLEAR REGULATORY COMMISSION
<E REGION V of
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1990 TJ. CALIFORNI A BOUL EVARD SUITE 202, W ALNUT CREEK PLAZA
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WALNUT CREEK, CALIFORNI A 94596 September 10, 1979 Docket flos. 50-133 50-275 50-323 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: fir. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
The enclosed Circular tio. 79-18 is forwarded to you for information.
fio written response is required.
Should you have any questions related to your understanding of the rccommendations on this matter, please contact this office.
Sincerely,
[T N ~; I,
R. H. Engelken Director
Enclosure:
IE Circular tio. 79-18 cc w/ enclosure:
W. Barr, PG&E W. Raymond, PG&E R. Ramsay, PG&E - Diablo Canyon ggg j^,g;3 E. Weeks, PG&E, Humboldt Bay
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J. D. Worthington, PG&E 7909210/g2
Accession ?!o: 7908200385 SSINS fio. 6830 UNITED STATES fiUCLEAR REGULATORY C0 MISSION OFFICE OF IrlSPECTION AND ENFORCEMEtlT UASHINGTON, D.C.
20555 September 10, 1979 IE Circular No. 79-18 PPCPEP INSTALLATICN OF TARGET P0CK SAFETY-PELIEF VALVES Description of Circumstances:
As a result of HRC 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 autonatic 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 tenperature environment for the elastoneric 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 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 is significant with respect to primary DUPLICATE DOCUMENT %oM*1 response analyses. Although the report three-stage Target Rock safety-relief i Entire document previously entered of insulation are similarly applicable into system under:
valves.
ANO N OS200385 The second potential problem was recent The licensee event report indicated the No. of pages:
N design two-stage valve resulted in prev
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