ML19208B259
| ML19208B259 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/10/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| NUDOCS 7909190425 | |
| Download: ML19208B259 (1) | |
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UNITED STATES
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Docket No. 50-271 SEP 101379 Vermont Yankee Nuclear Power Corporation ATTN:
Mr. Robert H. Groce Licensing Engineer 20 Turnpike Road Westborough, Massachusetts 01581 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, hf_
n oyce H. Grier
- Director
Enclosures:
1.
IE Circular No. 79-18 2.
List of IE Circulars Issued in Last Six Months cc w/encls:
W. F. Conway, Plant Superintendent Ms. J. Abbey, Technical Secretary A. Z. Roisman, Natural Resources Defense Council fr/3059 7909190 26
ENCLOSURE 1 Accession No: 7908200385 SSINS No. 6830 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 is that tne 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 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 revea'- -
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a cause condensation to accumulate in the p results in delaying the opening of the ma -l DUPLICATE DOCUMENT3*/3060 lEntire document previously entered sinto system under:
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