ML19208B605
| ML19208B605 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 09/10/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 7909210059 | |
| Download: ML19208B605 (1) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION y, 3,,
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'.r REGION 111 8
799 ROOSEVELT ROAD 0,
CLEN ELLYN, ILLINOIS 60137 o
Docket No. 50-329 Docket No. 50-330 Consumers Power Company ATTN:
Mr. Stephen H. Howell Vice President 1945 West Parnall Road Jackson, MI 49201 Gentlamen:
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 recommendations on this matter, please contact this office.
Sincerely, Q } )A 0-_ -
(/ James G. Kep"pTer Director
Enclosures:
1.
IE Circular No. 79-18 2.
List of IE Circc'.rs Issued in the Last Six Months cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSlc TIC Ronald Callen, Michigan Public Service Commission Dr. Wayne E. North Myron M. Cherry, Chicago 384052
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Accession No: 7908200385 SSIllS No. 6830 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT k'ASHINGTON, D.C.
20555 September 10, 1979 IE Circular No. 79.t8 Pi?0PEPINSTALLATIONOFTARGETROCKSAFETY-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 sa#rty-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 insuletion was installed on the valve.
The excessive insulation caused excessive hect to be retained producing a higher temperature environment for the elastomeic diaphragm which resulted in accelerated deterioration of the elastomer. Failure of the elastomeric diaphragm, makes the valve inoperable in the power-ooeration mode (i.e. manuai 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 accor, dance with the manufacturer's recommendations.
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A recent licensee event report f'om the Monticello facility identified a potential problem resulting fror. 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 vclve was discovered to be exceeding its design delay time for opening.
Subsequent inspection and testing of the valve revealed that insufficient insulati n may cause condensation to accumulate in the pressure venting ports which then results in delaying the opaning 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 val 8 V "mm%r1%fr 6s of_ insulation are similarly applicable to valves.
DUPLICATE DOCUMENT g.yjg,g The second potential problem was recently Entire document previously entered The licensee event report indicated that into systera under:
design two stage valve resulted in preven ANO MOMOb3M No. of pages:
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