ML20154L897
| ML20154L897 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/19/1988 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-121, NUDOCS 8809260337 | |
| Download: ML20154L897 (2) | |
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Log # TXX-88671 File # 10110
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903.10 Ref.#10CFR50.55(e) 7t/ELECTRlC September 19, 1988 II,'" Sdk"$,,,
w U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 CLARIFICATION OF 6.9KV/480V i'RANSFORMER BUS BAR CLEARANCE SDAR: CP-87-121 (SUPPLEMENTAL REP 0AT)
Gentlemen:
On January 6, 1988, TV Electric report logged TXX-88025 provided notification of a reportable deficiency hvolving the 6.9KV/480V transformer bus bar clearance.
The latest repoit on this issue, logged TxX-88627, dated Seatember 1, 1988, provided an update on the corrective action implementation scledule. The purpose of this report is to clarify the response in TXX-88627 concerning current work activities.
In TXX-88357 dated March 31, 1987, TU Electric stated thac the Westinghouse oreliminary design analysis indicated that the present transformer bus bar configuration would remain functional during a seismic event.
- However, TU Electric conservatively elected to modify the transformer design to establish additional design safety margin.
The transformers of concern are located on the 810' and 852'6" elevations of the Unit 1 Safeguard 8uilding.
The minimum bu., bar clearance required is 0.375 inch. Westinghouse utilized the Required Response S)ectrum (RRS) for elevation 852' 6" to calculate the bus bar clearance for tie transformers at the 810' and 852' 6" elevations.
The resulting clearance was 0.393 inch.
To obtain additional safety margin, TV Electric chose to modify the transformers both at the 810' and 852' 6" elevations.
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s TXX 88671 September 19, 1988 Page 2 of 2 Upon further investigation, TV Electric recognized that modifying the transforrors at the 810' elevation may not be justified because the seismic l
excitation would be less than at the 852' 6" elevation.
Therefore if the clearance was calculated using the RRS at the 810' elevation, it would be greater.
Subsequent calculations using the RRS at the 810' elevation resulted I
in a calculated clearance of 0.59 inch.
Thus, based on this calculated l
clearance, TU Electric decided that modification to the transformers at the 810' elevation was not required.
Very truly ours,
/NA( umue W. G. Counsil VPC/gj c - Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3) e
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