ML19350B148
| ML19350B148 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 03/13/1981 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Hancock J FLORIDA POWER CORP. |
| References | |
| NUDOCS 8103190880 | |
| Download: ML19350B148 (1) | |
Text
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^ /pa rrog*q UNITED STATES u
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NUCLEAR REGULATORY COMMISSION g.g 7') y,gjrfj;. g e
REGION 11 e.
101 MA91ETTA ST., N.W.. SulTE 3100 Y ' 'Q ATLANTA, GEORGIA 303o3 e
MAR 131981 In Reply Refer To:
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Florida Power Corporation
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ATTN:
J. A. Hancock, Assistant P
Vice President Nuclear Operations
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'e Gentlemen:
The enclosed IE Information Notice No. 81-05 contains information that may be applicable to your facility regarding the consequences of a degraded dc 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 you have any questions regarding this information notice, please contact this office.
Sincerely,
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James P. O'Reilly Director
Enclosures:
1.
IE Information Notice No. 81-05 2.
List of Recently Issued IE Information Notices cc w/ encl:
D. C. Poole, Nuclear Plant Manager 5
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SSINS No.:
6835 Accession No.:
8011040271 IN 81-05
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UNITED STATES e9 NUCLEAR REGULATORY COMMISSION 29 eu as 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 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 [1.e., total loss of both alternating current (ac) and de power].
.Since the piant was in.a normal mode.of_ operation, dc.p:wer was being supplied by'the ac syste'm via the battery chargers; therefore, de power was never interrupted during this period. Nevertheless, as described later, the safety of the plant was-jeopardized. A loss of offsita power during this period would, in the. absence of manual a.ction,_ result in_the loss of all control power.
blocking the automatic transfe'r of~ pow ~er'to the onsite diesel generators In many designs, such losses would also block the starting of the diesels.
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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
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from the diesei generators to their emergency buses and the required down stream y
load breakers.)' Ouring this time the ability of the plant to remove decay heat would bezseverely 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 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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4 IN 81-05 March 13, 1981 Page 2 of 2 Plants designed to conform with Regulatory Guide l'.47, " Bypassed and Inoperable Status Indication for Nuclear Power Plant Safety," will autcmatically 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 install annunciators -in the control room that will alert the operator whenever a station battery has.been disconnected from its bus.
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-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 Regier.al Office.
Attachment:
j Recently issued IE Information Notices t
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s Attachment IN 81-05 March 13, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No.
Subject Issue Issued to 81-C6 Failure of ITE Model 3/11/81 All power reactor K-600 Circuit Breaker facilities with an OL or CP 81-04 Cracking in Main Steam 2/27/81 All power reactor Lines facilities with an OL 81 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 HFA Relays OL or CP.
' 80-45
. Potential Failure of
' 12/17/80 All PWR facilities BWR Backup Ma'nual Scram with an GL or CP Capability 12/16/80 All PWR facilities 80-44
- Actuation of ECCS.in the-~
with an OL or CP Recirculation: Mode.While in Hot Shutdown-w 80 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 11/24/80 All power reactor Hydraulic Snubber Fluid facilities.with an OL or CP OL = Operating ' icenses L
CP = Construction Permits w., c a..,
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