ML19208B611
| ML19208B611 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 09/10/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Gerstner W ILLINOIS POWER CO. |
| References | |
| NUDOCS 7909210067 | |
| Download: ML19208B611 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION g.* N;'-'/j(, [g e
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i' 799 ROOSEVELT ROAD
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GLEN ELLYN. ILLINOls 60137 o
Docket No. 50-461 Docket No. 50-462 Illinois Power Company 4TTN:
Mr. W. C. Gerstner Executive Vice President 500 South 27th Street Decatur, IL 62525 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 recomruendations on this matter, please contact this office.
Sincerely,
% %$n A=
c/ James G. Ke$ler Director
Enclosures:
1.
IE Circular No. 79-18 2.
List of IE Circulars Issued in the Last Six Months cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Mr. Dean Hansell, Office of Assistant Attorney General 384103 N9092IO 067 Q
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~ Accession No: 7908200385 SSINS No. 6830 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 September 10, 1979 IE Circular No. 79-18 pit 0PERINSTALLATIONOFTARGETROCKSAFETY-RELIEFVALVES 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 remote air actuator.
The Target Rock safety-relief valve is a dual purpose valve in that overpressure respo'tse 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 Bulletire 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 envi.onment 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.
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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 event at Monticello involved the three-stage Target Rock safety-relief v ' ~ '
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of insulation are similarly applicable gg[g valves.
DUPLICATE DOCUMENT The second potential problem sas recentl Entire document previously entered The licensee event report indicated tha
.into system under:
design two-stage valve resulted in prev ANO 49 0M.O O M 6 1
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