ML17296B296
| ML17296B296 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/13/1981 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| References | |
| NUDOCS 8103200042 | |
| Download: ML17296B296 (7) | |
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0 UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V 1990 N. CALIFORNIABOULEVARD SUITE 202, WALNUTCREEK PLAZA WALNUTCREEK, CALIFORNIA94599 Narch 13, 1981 Docket Nos. 50-528, 50-529, 50-530 Arizona Public Service Company P. 0.
Box 21666 Phoenix, Arizona 85036 Attention:
Mr. E.
E.
Van Brunt, Jr.
Vice President, Nuclear Projects 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, R.
H. Engelken Director
Enclosures:
l.
IE Information Notice No. 81-05 2.
List of Recently Issued IE Information Notices cc w/enclosures:
F.
W. Hartley, APS 8~099OO00%
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SSINS No.:
6835 Accession No.:
8011040271 IN 81-05 UNITED, STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 March 13, 1981 IE INFORMATION NOTICE NO. 81-05:
DEGRADED DC SYSTEM AT PALISADES
~Per ose:
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 noticealerts holders of operating licenses and construction permits of an event that degraded the dc system at the Palisades facility and jeopardized plant safety.
Descri tion of'ircumstances:
On January 6, 1981, while performing monthly surveillqnce 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 apptoxi-mately one hour.
We view this personnel error as a common-mode, failure that, if left uncorrected, would lead to a complete station blackout Oi.e., total loss of both alternating current (ac) and 'dc powero.
Since the plant was in a normal mode of operation, dc power was, bei,ng 'supplied by the ac system via the battery chargers; therefore, dc power was never
'nterrupted during this period.
Nevertheless, as described later, the safety of the plant was jeopardized.
A loss of offsite power during this per iod 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'he diesefs;
- 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 the required down stream load breakers.)
During this time the ability of the p1ant 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'ffsite power would lead to an undetected common-mode failure.
Such a failure would be difficult to diagnose, thereby limiting the operator,'s abi.lity 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 remova1.
IN 81-05 March 13, 1981 Page 2 of 2 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, Pal.isades is. planning to, install 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.notificatzon of a possibly significant matter that is still under review by the NRC staff.
Recipients should review the information for possible applicabi]i'ty 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
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RECENTLY ISSUED I E INFORMATION NOTICES Attachment IN 81-05 March 13, 1981 Information Notice No. 81-06 81-04 81-03 81-02 81-01 Sub ect Failure of ITE Model K-600 Circuit Breaker Cracking in Main Steam Lines Checklist for Licensees Making Notificati ons of Significant Events in Accordance with 10 CFR 50.72 Transportation of Radi ography Devi ces Possible Failures of General Electric Type HFA Relays Date of
'ssue 3/13/81 2/27/81 2/12/81
. 1/23'/81.
1/16/81
'Issued'to'
'll power reactor faci.lities with an OL or'P.
All power reactor faciliti,es with an OL
'll power reactor facj]ities with an OL
.All Radiography l.icenqees All power reactor facil.i.ties with an OL or CP.
80-45 80-44 Potential Failure of BWR Backup Manual Scram Capabi 1 ity Actuation of ECCS in,the Recirculation Mode While in Hot Shutdown 12/17/80.,
All I'WP, facilities with. an, OL or CP 12/16/80,.
All Pl,'JR, faci,lities with an OL or CP 80-43 Failures of the Continuous 12/5/80.
Water Level Monitor for the Scram Discharge Volume at Dresden Unit No.
2 All power I"eactor facilities wi.th an OL or CP 80-42 Effect of Radiation on Hydraulic Snubber Fluid ll/24/80.
Al.l power reactor facili,ties wi.th an OL or CP OL = Operating Licenses CP
= Construction Permits
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