ML20195H808
| ML20195H808 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 01/11/1988 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-91, TXX-88007, NUDOCS 8801200357 | |
| Download: ML20195H808 (2) | |
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F7 Log # TXX-88007 2
C File # 10110
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January 11, 1988 V. S. Nuclear R'egulatory Commission Attn: Document Control Center Washington, D.C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION C0CKET N05. 50-445 AND 50-446 STA TUP TRANSFORMER OVERLOAD SDAR: CP-87-91 (INTERIM REPORT)
Gentlemen:
On September 3, 1987, we verbally notified your Mr. H. S. Phillips of c deficiency involving the overload capacity of the startup transformers. Our latest interim report was logged TXX-6787, dated October 5, 1987.
After further evaluation we have termined that this deficiency is reportable pursuant to 10CFR50.55(e).
The required information follows.
DESCRIPTION OF DEFICIENCY This deficiency was discovered during preparation of the Design Basis Document (DBD-EE-038) for the startup transformers.
Specifically, a discrepancy was identified between licensing commitments and the transformers' Specification (2323-ES-2A and 2B), which indicates that the loading conditions for the startup transformers may exceed their overload capacity.
FSAR Section 8.3.1.1.1 states that the startup transformers are rated for a 49% overload, which results in an overload value of 63,800 KVA.
However, the postulated overload, based on as-built design, is 72,600 KVA.
The cause of this deficiency is that the original Startup and Auxiliary Transformer Load Study Calculation (III-7, Rev. 3) and Bus Feeder Calculation (VII-2, Rev. 3) accepted the overload conditions without sufficient evaluation or determination of the impact to the transformer bushings or to the plant voltage profile. We have reviewed other transformers under our Corrective Action Program, and have determined that this deficiency is limited to the identified startup transformers.
8801200357 880111 PDR ADOCK 05000445 ia 100 North Ohr Street LR 81 Dallas, Texas 15.'01
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TXX-88007 January 11, 1988 Page 2 of 2 SAFETY SIGNIFICANCE In the event that actual overload were to exceed the transformers capacity, the potential exists for the faMure of the transfonners, resulting in the loss'of offsite power.
Had this condition remained uncorrected, it could have adve sely affected the operational safety of the plant.
CORRECTIVE ACTION We are currently revising the AC distribution system to include two additional startup transfonners and associated cabling, and to reallocate CPSES Unit I and 2 emergency and. normal bu:es between the existing startup transformers and the new transformers.
This will eliminate the transformer overloading problem.
We will provide a statu of this activity and schedule for the completion of corrective action in our next report, which we will subniit by April 15, 1988.
In order to preclude recurrence of the h conditions, design control procedures have been revised to require that calculations be performed based on controlled input data, and that the calculations be checked and independently reviewed to ensure accuracy.
No further corrective action is necessary.
Very truly yours,
@/D W. G. Counsil WJil/grr c-Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3)