ML19270E960
| ML19270E960 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 12/19/1978 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Short T OMAHA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 7901040174 | |
| Download: ML19270E960 (1) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION LPDR WF t,
REciON iv 7,
c 311 RYAN PLAZA DRIVE, SUITE 1000 N$1C o,,..
AR LiNGTON, TEXAS 76011 December 19, 1978 Docket No. 50-285 Omaha Public Power District ATTN: Mr. T. E. Short, Assistant General Manager 1623 Harney Street Omaha, Nebraska 68102 Gentlemen:
The enclosed IE Bulletin 78-14 is fomarded to you for infomation. No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, k$ ?$$
Karl V. Seyfrit Director
Enclosures:
1.
List of IE Bulletins Issued in 1978 7 9010 43 4/W/
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 OF 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 insertior, 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, 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 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 tha 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 1 (January 30,1976),
addressing 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 Duna-N discs O
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