ML19290C011
| ML19290C011 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 11/16/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8001090035 | |
| Download: ML19290C011 (1) | |
Text
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UNITED STATES CENTRAL FILES
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NUCLEAR REGULATORY COMMISSION PDR:HQ 7
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November 16, 1979 Docket No. 50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Centlemen:
This IE Infomation Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will distribute this Notice to their operating personnel and will review the information for possible applicability to their facilities.
No specific action or response is requested at this time.
However, we anticipate that further NRC evaluations will result in issuance of an IE Circular, Bulletin, or NRR Generic Letter in the near future which will recommend or request specific applicant or licensee actions.
If you have questions regarding the catter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
,0 Karl V.
yfrit Director
Enclosures:
1.
IE Infomation Notice No. 79-29 2.
List of IE Information Notices Recently Issued cc:
D. W. Warenbourg, Nuclear Production 1729 013 Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance 8 001090 h[
SSINS No.: 6300 Accession No.:
7910250490 UNITED STATES fid$f NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 November 16, 1979 IE Information Notice No. 7'9-29 LOSS OF NONSAFETY-RELATED REACTOR COOLANT SYSTEM INSTRUMENTATION DURING OPERATION This notice ontains information regarding a loss of reactor coolant system instrumentat en as a consequence of a failure of a static transfer switch to transfer to na alternate supply.
At 3:15 p.m. on November 10, 1979 with Unit 3 of the Oconee Station at 100 percent power, the main condensate pumps tripped, apparently as a result of a technician performing maintenance on the hotwell level control system. This led to reduced feedwater flow to the steam generators, which resulted in a high reactor coolant system (RCS) pressure reactor trip and simultaneous turbine trip at 3:16:57 p.m.
At 3:17:15 p.m., the inverte r power supply, nonsafety-related, feeding all power to the integrated control system (ICS) tripped and failed to automatically transfer its loads from the DC power source to the regulated AC power source.
The inverter had tripped due to blown fuses, resulting in loss cf RCS indicators and recorders in the control room, except one wide range RCS pressure recorder.
This condition existed for approximately three minutes, until an operator could reach the equipment rcom and switch the inverter manually to the regulated AC source.
As a result of the power failure to the ICS, all valves controlled by the system assumed their respective fail positions.
This resulted in a cool down of the RCS to 1635 psi and 530 degrees F.
The operator, expecting this condition, started all makeup pumps and opened the associated high presst:re injection valves to the RCS which limited the rate of RCS pressure reduction and associated reduction in pressurizer level.
At 3:20:42 p.m.,
power was restored to the ICS and RCS conditions were restored.
Although RCS cooldown limits were exceeded, the pressurizer and steam generators did not ge dry, and at least 79 degrees F subcooling was maintained during this event.
No engineered safety features actuation setpoints were reached, and, except for the components discussed above, no component malfunc-tions occurreo.
The licensee has installed a redundane acrromechanical transfer switch between the loads and the regulated supp'-
This switch will actuate and power the loads from the regulated supp?
ald the original static switch fail to transfer.
1729 014
IE Information Notice No. 79-29 Date: November 16, 1979 Page 2 of 2 Longer term resolution of the need or desirability to separate these instruments onto diverse electrical supplies or to provide redundant inscrumentation display channels for operator use from essential power supplies are also under consideration.
It is anticipated that further NRC evaluations will result in issuance of an IE Circular, Sulletin, or NRR Generic letter in the near future which will recoc=end or request specific applicant or licensee actions.
This Information Notice is provided to inform licensees of a possibly significant matter.
It is expected that recipients will disseminate the information to all operational personnel working at their licensed facilities.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
No written response to this Information Notice is required.
I729 0i5 s
IE Informatic
- ir. No. 79-29 November 16, 19,9 LISTING OF IE LVFORMATION NOTICES ISSUED IN 1979 Info rmation Subj ect Date Issu o To Notice No.
Issued 79-20 NRC Enforcement Policy 8/14/79 All Holders of Reactor (Rev. 1)
NRC Licensed Individuals Operating Licenses (OLs) and Construction Permits (cps), Research Reactors, Test Reactors licensees with Licensed Operators 79-21 Transportation and 9/7/79 All power and research Commerical Eurial reactors with Operating of Radioactive Material License (OL) 79-22 Qualification of Control 9/14/79 All power reactor Systems facilities with an Operating Licenses (OL) and Construction Permits (CP) 79-23 Emergency Diesel Generator 9/26/79 All power reactor Lube Oil Coolers facilities with an Operating License (OL) or Construction Permit (CP) 79-24 Overpressurization of 9/28/79 All power reactor Containment of a PWR Plant facilities with a After a Main Stream Line Construction Permit (CP)
Break 79-25 Reactor Trips at Turkey 10/1/79 All power reactor Point Unit 3 and 4 facilities with an Operating License (OL) or a Construction Permit (CP) 79-26 Breach of Containment 11/5/79 All power reactor Integrity holding Operating License (OL) and Construction Permits (cps)79-12A Attempted Damage to New 11/19/79 All Fuel Facilities, Fuel Assemblies research reactors, and 1790 014 Power reactors with an I L/
UlU Operating License (OL) or Construction Permit (CP)
Enclosure