ML19350B152
| ML19350B152 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 03/13/1981 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 8103190888 | |
| Download: ML19350B152 (1) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION k >
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REGION 11
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MAR 131981 O
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In Reply Refer To:
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South Carolina Electric and Gas Company hg im ATTN:
T. C. Nichols, Jr., Vice President Power Production and Systems Operations P. O. Box 764 Columbia, SC 29218 Gentlemen:
The enclosed IE Information Notice No. 81-05 contains information that may be applicable to your facility regarcing.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 you have any questions regarding this information notice, please contact this office.
Sincerely,
'w j' James P. O'Reilly Director
Enclosures:
1.
IE.Information Notice No. 81-05
~2.
' List %f'Recdntly Issued ~
IE Information Notices cc w/ encl:
A. A. Smith, Site QA Coordinator J. B. Knotts, Jr
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- 0. S. Bradham, Manager Nuclear Operations B og,9g l
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6835 Accession No.:
8011040271.
IN 81-05 d]#^[d ui "A
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UNITED STATES NUCLEAR REGULATORY COMMISSION m-0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 March 13, 1981 IE INFORMATION NOTICE No. 81-05:
0EGRADED DC SYSTEM'AT PALISADES Parpose:
The intent of this notice is tc enhance nuclear power plant safety by isoroving 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, both station batteries, maintenance personnel inadvertently opened the breakers from both station batteries to their 125 volt de buses and left them open for approxi-
-mately one hour. We view this personnel error as a common-made failure that, if left uncorrected, would lead to a complete station blackout [1.e., total loss of both alternating current (ac) and dc power].
Since the plant was in a normal mode of operation,.dc power was being supplied by the ac system 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 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.
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the Phlis'ad~'s 'dssign"wodid' hot block the ' starting 'of ~ the" diesels;-
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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., canually closing the breakers from the diesel generators to their. emergency buses and the required down stream y
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 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 Page 2 of 2 i
Plants designed to conform with Regulatory Guide 1.47, " Bypassed and Inoperable Status Indication for Huclear Power Plant Safety," will automatically alart 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 innunciators 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 f
. additional information regarding this matter, contact the Director of the
. appropriate NRC Regional Office.
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Attachment:
Recently issued IE Information Notices 9
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Attachment TN 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 3/11/81 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 81-03 Checklist for Licensees 2/12/81 All power reactor Making Notificati.ons of facilities with an Significant Events in OL Accordance with 10 CFR 50.72 81-02 Transportation of 1/23/81 All Radiograrhy 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 1 BWR Backup Manual Scram with'an OL or CP Capability 44 Actuation of ECCS in-the 12/16/80 All PWR facilities Recirculation Mode-While with an OL or CP i@.HotShutdown
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80-43 Failures.of the Continuous 12/5/80 All power reactor Water Level Monitor for facilities with an the Scram Discharge Volume
' 0L or CP
-at Dresden Unit No. 2 80 Effect of Radiation on' 11/24/80
-All power reactor
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Hydraulic Snubber Fluid facilities with an OL or CP OL = Operating. Licenses CP =-Construction Permits s
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