ML19261A288
| ML19261A288 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe, Vermont Yankee |
| Issue date: | 12/19/1978 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R VERMONT YANKEE NUCLEAR POWER CORP., YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 7901030059 | |
| Download: ML19261A288 (1) | |
Text
T&n p n aso,
UNITED STATES v
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NUCLEAR REGULATORY COMMISSION REGION I E*
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$31 PARK AVENUE e,
f KING OF PRUSSI A, PENNSYt.V ANI A 19406 December 19, 1978 Docket No. 50-271 Vermont Yankee Nuclear Power Corporation ATTN:
Mr. Robert H. Groce Licensing Engineer 20 Turnpike Road Westborough, Massachusetts 01581 Gentlemen:
The enclosed Bulletin 78-14 is forwarded to you for action.
A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, u
k4 n
Boyce H. Gr1
- Director
Enclosures:
1.
List of IE Bulletins Issued in 1978 cc w/encls:
W. F. Conway, Plant Superintendent S. D. Karpyak, Manager, Administrative and Technical Liaison A. Z. Roisman, Natural Resources Defense Council 79010300Y[
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 78-14 Date:
December 19, 1978 Page 1 of 3 DETERIORATION 0F BUNA-N COMPONENTS IN ASCO S0LEN0 IDS Description of Circumstances:
Following a reactor scram at the Monticello 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 ai from the scrcm valves.
A similar event occurred during scram testing on June 5,1978.
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 shutdcwn on July 28, 1976.
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 soienoid 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, SIL 128 (March 31,1975) and SIL 128 Revision I (January 30,1976),
addressing the deterioration through natural aging of Buna-N components in CRD scram pilot valves.
These letters recomended that a maintenance program be adopted which replaced certain Buna-N components it. scram pilot valves on a regularly scheduled basis.
However, the Buna-N discs h@ryo?'
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