TXX-6710, Interim Deficiency Rept CP-87-51 Re 480 Volt Containment Electrical Penetration Backup Protection.Initially Reported on 870729.Caused by Design Company Failure to Properly Translate Reg Guide 1.63 Requirements Into Drawings & Specs
| ML20238C585 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/02/1987 |
| From: | Counsil W, Keeley G TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| RTR-REGGD-01.063, RTR-REGGD-1.063 CP-87-51, TXX-6710, NUDOCS 8709100222 | |
| Download: ML20238C585 (3) | |
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lllllll' 'llllllllll Log # TXX-6710 4
File # 10110 E
E 908.3 1UELECTRIC wmiam c. cmmsa September 2, 1987 Executive %cc f>esident U. S. Nuclear Regulatory Commission 1
Attn: Document Control Desk l
Washington, D.C. 20555 l
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 l
480V CONTAINMENT ELECTRICAL PENETRATION BACKUP PROTECTION SDAR: CP-87-51 (INTERIM REPORT)
Gentlemen:
On July 29, 1987, we verbally notified your Mr. H. S. Phillips of a deficiency involving backup protection for the 480V containment electrical penetrations.
Our last report was logged TXX-6683 dated August 28, 1987. On September 1, 1987, we verbally notified your Mr. H. S. Phillips that this deficiency was reportable under the provisions of 10CFR50.55(e) and the required information follows:
1 DESCRIPTION OF PROBLEM The subject 480V buses provide primary and backup protection to the penetrations when in the normal operating mode.
However, during a review of the 480V Auxiliary One Line Diagram for Safeguard Buses (Drawing No. 2323-El-0005) it was discovered that when the main feeder breaker to any of these buses is taken out of service and the tie breaker is closed (accomplished through manual action), there is no backup protection provided to the containment penetrations located on the alternate bus being fed through the tie breaker.
This is due, in part, by the procedure (governing the above manual action) not specifically requiring the penetration loads to be tripped prior to closing the tie breaker.
The present design uses the main feeder breaker as the backup protection with a trip signal coming from relays (50/51) on the breakers feeding the loads in the reactor containment.
When the main breaker is open and the tie breaker is closed supplying power to the bus, there is no trip signal to the tie breaker, and hence no tackup protection.
The root cause of this deficiency is a failure of the design organization to properly translate into drawings and specifications the requirements of Regulatory Guide 1.63, " Electrical Penetration Assemblies in Containment Structures for Light-Water-Cooled Nuclear Power Plants", and IEEE Standard 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations".
B709100222 870902 PDR ADOCK 05000445-S PDR b' g y MD North Obvc Street LB Si Dallas, Texas 75201
.lo i
f TXX-6710 September 2, 1987 Page 2 SAFETY IMPLICATION When operating with the tie breaker closed, the containment penetrations located.on the alternate bus being fed through the tie breaker would not be provided with backup protection.
As currently configured, the failure of a single overcurrent protection device associated with a containment penetration, when being supplied power via the tie breaker, could result in excessive currents and failure of the containment penetration.
This issue represents a significant final design deficiency as approved and released for construction and, were it to have remained uncorrected, coul6
'have adversely affected the safety of plant operations.
CORRECTIVE ACTION
. f.,
The generic implications of this deficiency involve the effectiveness qf l
previous design control measures.
This issue and the conformance of the final design to' established licensing and regulatory requirements, will be asses. sed in the Electric Project Status Report issued as a result of the CPSESQ Corrective Action Program.
4' We are continuing our evaluation to determine the corrective action needed to bring the design / procedures into compliance with Regulatory Guide 1,63 and IEEE STD 279-1971. Osr corrective action and schedule for implementation will be provided in our next report.
Our next report on this issue will be submitted no later than December 18, 1987.
Very truly yours, Y
W. G. Counsil l
ll b.
U By:
G. S. Keeley C x Manager,NuclearLicVnsing l
WJH/mlh I
c - Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3)
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