ML19305D576
| ML19305D576 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/31/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8004150237 | |
| Download: ML19305D576 (1) | |
Text
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ARLINGTON, TEXAS 76012 STATE March 31, 1980 Docket No. 50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
This IE Information Notice is provided as a notification of a possibly significant matter.
It is expected that recipients will review the information for possible applicability to their facilities.
No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, o
?
. V. Seyfrit, j
Director
Enclosures:
1.
IE Information Notice No. 80-12 2.
List of IE Information Notices Recently Issued l
cc:
D. W. Warembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station l
P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance 8004150 2 3 7
SSINS No.: 6870 Accession No.:
UNITED STATES 8002280654 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information Notice No.: 80-12 March 31, 1980 Page 1 of 1 INSTRUMENT FAILURE CAUSES OPENING OF PORV AND BLOCK VALVE Description of Circumstances:
On August 13, 1979, during full, steady-state power operation at the Connecticut Yankee Haddam Neck Plant, the pressurizer power operated relief valve (PORV) and its isolation (block) valve opened as a result of failure of a light source in the sigma bistable of the pressurizer pressure controller.
The failure of the light source was equivalent in control system response to an overpressure condition in the pressurizer. By system design, both PORV and block valves are closed during normal operation and therefore both valves are required to open in response to an overpressure condition.
The opening of the PORV and block valve allowed the pressurizer pressure to drop from its normal value of 2000 psig to 1950 psig before the PORV and block valves could be closed.
The operator immediately overrode the open signal to the valves and closed the valves to stop depressurization.
The pressurizer pressure then immediately returned to normal.
The light source was subsequently replaced in the bistable and the pressure control system was returned to normal.
The licensee reported that failures of light sources in the bistable of this pressure controller and in other similar plant bistables had been experienced previously.
Subsequently on February 4, 1980, a spurious signal from the pressure controller caused both PORV and block valve to open.
In both events, the operator responded immediately and effectively to limit the conse-quences of the event to a relatively mild pressure transient on the reactor coolant system.
The licensee also indicated that it had changed out the type of bistable with a solid state design which does not depend on a light source and which is expected to be more reliable.
This information is provided as notification of a possibly significant matter.
It is expected that recipients will review the information for possible applicability to their facilities. No specific action or response is requested at this time.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
i i
1 1
r IE Information Notice No. 80-12 March 31, 1980 LISTING OF RECENTLY ISSUED IE INFORMATION NOTICES Info rmation Subject Date Issued To Notice No.
Issued 80-06 Notification of Significant 2/27/80 All holders of Reactor Events Operating Licenses (OLs) and to near term Operating Licenses (OL) applicants 80-07 Pump Shaft Fatigue Cracking 2/29/80 All Light Water Reactor Facilities holder power reactor Operating Licenses (OLs) and Construction Permits (cps) 80-08 The States Company Sliding 3/7/80 All power reactor Link Electrical Terminal facilities with an Operating License (OL) or a Construction Permit 80-09 Possible Occupational 3/7/80 All holders of power Health Hazard Associated reactor Operating With Closed Cooling Systems Licenses (OLs) and For Operating Power Plants near term Construction Permits (cps) 80-10 Partial Loss of Non-Nuclear 3/7/80 all Power reactor Instrument System Power facilities holding Supply During Operation Operating Licenses (OLs) and Construction Permits (cps) 80-11 General Problems with ASCO 3/14/80 All holders of Reactor Valves in Nuclear Application OL, CP, fuel fabrica-Including Fire Protection tion and processing Systems facilities Enclosure