ML19350B497
| ML19350B497 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/13/1981 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Bryan J UNION ELECTRIC CO. |
| References | |
| NUDOCS 8103200662 | |
| Download: ML19350B497 (2) | |
Text
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UNITED STATES 50 '#b
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NUCLEAR REGULATORY COMMISSION 1
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Gentlemen:
The enclosed IE Information Notice No. 81-05 contains information that may be applicable to your facility regardi..g the consequences of a degraded de system. No specific actions or responses are requested at this time; however, pending the results of an ongoing NRC staff evaluation of this matter, further licensee actions may be requested.
Should yet have any questions regarding this information notice, please contact t'is office.
Sincerely, d Sa. h'-
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,,. James G. Keppler Director
Enclosure:
IE Information Notice No. 81-05
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Y v.s.g Docket No. 50-483 Docket No. 50-486 k
y Union Electric Company ATTN:
Mr. John K. Bryan Vice President - Nuclear Post Office Box 149 St. Louis, MD 63166 cc w/ encl:
W. II. Weber, Manager Nuclear Construction Central Files AD/ Licensing AD/ Operating Reactors PDR Loca PDR NS' C
Regions I & IV K. Drey Ronald Fluegge, Utility Division, Missouri Public Service Commission
e SSINS No.:
6835 Accession No.:
8011040271 IN 81-05 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
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March 13, 1981 IE INFORMATION NOTICE NO. 81-05:
DEGRADED DC SYSTEM AT PALISADES
Purpose:
The intent of this notice is to enhance nuclear power plant safety by improving the reliability of the direct current (dc) distribution system in nuclear power plants.
Toward this end, this information notice alerts holders of operating licenses and construction permits of an event that degraded the de system at the Palisades facility and jeopardized plant safety.
Description of Circumstances:
On January 6, 1981, while performing monthly surveillance tests on both station batteries, maintenance personnel inadvertently opened the breakers from both station batteries to their 125 volt dc buses and left them open for approxi-mately one hour. We view this personnel error as a common-mode failure that, if left uncorrected, would lead to a complete station blackout [i.e., total loss of both alternating current (ac) and de power].
Since the plant was in a normal mode of operation, de power was being supplied by the ac system via the battery chargers; therefore, dc power was never interrupted during this period.
Nevertheless, as described later, the safety of the plant was jeopardized.
A loss of offsite power during this period would, in the absence of manual action, result in the loss of all control power, blocking the automatic transfer of power to the onsite diesel generators.
In many designs, such losses would also block the starting of the diesels.
In contrast, the Palisades design would not block the starting of the diesels; however, the loss of. control power would block the connecting of the generators to their emergency buses so that a complete station blackout would still result.
In either case, the blackout would persist until the battery breakers were manually reclosed or manual actions taken (e.g., manually closing the breakers from the diesel generators to their emergency. buses and.he required down stream l
load breakers.) During this time the ability of the plant to remove decay heat would be severely restricted.
Since the tripping of the battery breakers is not annunciated in the Palisades control room, a subsequent loss of offsite power would lead to an undetected common-mode failure.
Such a failure would be difficult to diagnose, thereby limiting the operator's ability to take timely
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corrective action.
Consequently, an inordinate amount of time could be required to bring the plant to a normal mode of decay heat removal.
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IN 81-05 March 13, 1981 i
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Plants designed to conform with Regulatory Guide 1.47, " Bypassed and Inoperable Status Indication for Nuclear Power Plant Safety," will automatically alert the operator whenever a battery is disconnected from its bus, thereby precluding a Palisades type of event.
As a corrective measure, Palisades is planning to LJnstall annunciators in the control room that will alert the operator whenever a station battery has been disconnected from its bus.
The information herein is being provided as an early notification of a possibly significant matter that is still under review by the NRC staff.
Recipients should review the information' for possible applicability to their facilities.
If NRC evaluations so indicate, further licensee actions may be requested.
No written response to this Information Notice is required.
If you desire additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
Attachment:
Recently issued IE Information Notices 6
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Attachment IN 81-05 March 13, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No.
Subject Issue Issued to 81-06 Failure of ITE Model 3/13/81 All power reactor K-600 Circrit Breaker facilities with an OL or CP 81-04 Cracking in Main Steam 2/27/81 All power reactor 1
Lines facilities with an OL 81-03 Checklist for Licensees 2/12/81 All power reactor Making Notifications of facilities with an Significant Events in OL Accordance with 10 CFR 50.72 81-02 Transportation of 1/23/81 All Radiography Radiography Devices
- licensees 81-01 Possible Failures of 1/16/81 All power reactor General Electric Type facilities with an i
6 80-45 Potential Failure of 12/17/80 All PWR facilities BWR Backup Manual Scram with an OL or CP Capability 80-44 Actuation of ECCS in the 12/16/80 All PWR facilities
- Recirculation Mode While with an OL or CP in Hot Shutdown 80-43 Failures of the Continuous 12/5/80 All power reactor Water Level Monitor for facilities with an the Scram Discharge Volume OL or CP.
at Dresden Unit No. 2 80-42 Effect of Radiation on 11/24/8C All power reactor Hydraulic Snubber Fluid facilities with an OL or CP OL = Operating Licenses CP = Construction Permits 9
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