ML19308A186
| ML19308A186 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/19/1978 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7812290094 | |
| Download: ML19308A186 (1) | |
Text
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UNITED STATES g
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NUCLEAR REGULATORY COMMISSION 5
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E REGION V j
0, SulTE 202, W ALNUT CREED PLAZ A k,, #
,o 1990 N. CALIFORNI A BOULEVARD 4*e#
WALNUT CREEK, C ALIFORNI A 94596 December 19, 1978 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentl emen:
The enclosed IE Bulletin No. 78-14 is forwarded to you for 1nformation.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, c$~
7 R. H. Engelken Director
Enclosures:
1.
List of IE Bulletins Issued in 1978 cc w/ enclosures:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD hU 23 609(;[
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-. -. ~ - _. - -.. -
UNITED STATES NUCLEAR REGULATORY COM4ISSION OFFICE OF INSPECTION AND ENFORCDCIT WASHINGTON, D.C.
20555 Dece=ber 19, 1978 IE Bulletin No. 78-lt DETERIORATION OF BUNA-N COMPONENTS IN ASCO SOLENOIDS s
Deseviption of Circu= stances:
Following a reactor scram at the Monticello Nuclear Power Station on July 27, 1978, one control rod was determined to have a slow scrat While measuring the average control rod scra= insertion insertion ti=e.
times (as required by Technical Specificaticus), the same control rod failed to sers=.
Subsequent investigation revealed that a Buna-N disc Small in the scra= pilot valve solenoid core asse=bly had fractured.
pieces of the Buna-N caterial vedged between the core assembly and the valve pilot body. This prevented proper movement of the core assently (plunger), and thus prevented the valve from properly venting control air from the scra= valves. A similar event occurred during sera testing on June 5, 1978.
On both occasions the control rod failed to scran during control rod surveillance testing.
In these instances, had a scram occurred during normal operation of the reactor, the affected rods would have inserted by action of the backup scra solenoid valves.
The reactor vat, placed in cold shutdown on July 28, 1978. All of che sera = pilot solenoid valves and scram backup valves were disassembled and inspected. Six additional fractured Buna-N discs were found, all in scram pilot solenoid valves. Northern States Power Co=pany replaced the plunger Buna-N discs in all 2L2 sera = pilot valves and the 2 backup scram valves.
In additicn to the Monticello failures, similar events were recently reported fro = the Big Rock Point and Pilgrit facilities.
At Big Rock Point, two failures were experienced in October while at Pilgric one failure was found in July and two in December. All of these failurer were encountered during surveillance testing.
s i
General Electric had previously issued Service Informatier. Letters, SIL 128 (March 31, 1975) and SIL 128 Revision 1 (January 30, 1976),
j addressing the deterioration thBuna-N co=ponent s in CRD scram pilot valves. Th prott an be adopted which replat pilot valves on a regularly selg DUPLICATE DOCUMENT Entire document previously entered into system under:
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~NI'Z7A oz30 No. of pages:
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