ML19270E952
| ML19270E952 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 12/19/1978 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 7901040165 | |
| Download: ML19270E952 (1) | |
Text
CENTRAL FILES UNITED STATES PDR:HQ g#.N afou,D o
NUCLEAR REGULATORY COMMISSION LPDR
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R EGION IV
.. E 611 RYAN PLAZA DRIVE, SulTE 1000 NSIC 8
'+,*****,d December 19, 1978 Docket No. 50-267 Public Service Company. of Colorado ATTN: Mr. C. K. Millen Senior Vice President Post Office Box 840 Denver, Colorado 80201 Gentlemen:
The enclosed IE Bulletin 78-14 is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, h
G V
Karl V. Seyfrit Director
Enclosures:
1.
II Bulletin 78-14 2.
List of IE Bulletins Issued in 1978 7 9 0 t o 40 MS'd
UNITED STATES fiUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMEllT WASHINGTON, D.C.
20555 IE Bulletin No. 78-14 Date:
December 19, 1978 Page 1 of 3 DETERIORATION OF BUNA-N COMPONENTS IN ASCO SOLEN 0 IDS Description of Circumstances:
Following a reactor scram at the fbnticello Nuclear Power Station on July 27, 1978, one control rod was determined to have a slow scram insertion time. While measuring the average control rod scram insertion times (as required by Technical Specifications), the same control rod failed to scram. Subsequent investigation revealed that a Buna-N disc in the scram pilot valve solenoid core assembly had fractured.
Small pieces of the Buna-N material wedged between the core assembly and the valve pilot body. This prevented proper movement of the core assembly (plunger), and thus prevented the valve from properly venting control air from the scram valves.
A similar event occurred during scram testing on June 5, 1975.
On both occasions the control rod failed to scram 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 scram solenoid valves.
The reactor was placed in cold shutdown on July 28, 1978.
All of the scram 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 Company replaced the plunger Buna-N discs in all 242 scram pilot valves and the 2 backup scram valves.
In addition to the Monticello failures, similar events were recently reported from the Big Rock Point and Pilgrim facilities. At Big Rock Point, two failures were experienced in October while at Pilgrim one failure was found in July and two in December. All of these failures were encountered during surveillance testing.
General Electric had previously issued Service Information Letters, 128 (March 31, 1975) and LIL 128 Revision 1 (January 30,1976),
c" Jressing the deterioration through natural aging of Buna-N components in CRD scram pilot valves. These letters recommended that a maintenance program be adopted which replaced certain Buna-N components in scram pilot valves on a regularly scheduled basis. However, the Buna-N discs l
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