ML20246P364
| ML20246P364 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/05/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-88-41, IEIN-87-061, IEIN-87-61, TXX-89645, NUDOCS 8909110098 | |
| Download: ML20246P364 (2) | |
Text
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2 't M.E E Log # TXX-89645 1
2 File # 10110
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c 908.3 Ref. # 10CFR50.55(e)
RFELECTRIC September 5, 1989 Esecutive Vke l'ressient 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 W-2 TYPE CELL SWITCHES SDAR: CP-88-41 (FINAL REPORT)
Gentlemen:
On December 2,1988, TU Electric notified the NRC of a deficiency involving Westinghouse W 2 type cell switches. The latest report on this issue, logged TXX-89371, was submitted June 12, 1989.
It has been concluded that this deficiency meets the criteria for deportability pursuant to 10CFR50.55(e).
The required information follows.
Description On.0ctober 6, 1987, Westinghouse notified the NRC, via letter NS-NRC-87-3276, of a potential.10CFR Part 21 defect titled "W-2 Cell Switch Failures". On January 29, 1988 Westinghouse notified TU Electric by letter of a possible mechanical malfunction of Westinghouse W-2 cell switches in certain applications which might remain undetected without adequate surveillance or testing.
NRC Information Notice No. 87-61 Supplement 1 attributed the cause of switch failure to deformation of the spring retainer and resultant loss of spring tension.
TU Electric has conducted inspections of the CPSES Unit I safety _ related (Class IE) 480V switchgear per Westinghouse *s recommendations.
Four W-2 cell switches failed Westinghouse *s inspection requirements for continuity checks and operability _ requirements. The four switches were identified in a non-conformance report.
In addition, visual inspections of the spring mechanism (spring and spring retainer) in three other switches disclosed some signs of deformation.
TU Electric concluded that, since several W-2 cell switches which exhibited L
~some deformation passed the continuity and operability test, visual inspection of the switch internal structure is required to detect the subject defect.
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'TXX-89645-September 5, 1989 Page 2 of 2 Safety Isoljcations.
Failure of the W-2 cell switch could allow the switch to indicate that the breaker is in the " connected" position when the breaker has been moved to another position (i.e., " test position", " disconnected" or " removed")-. This may prevent the completion of safety related functions dependent on the cell switch control interlock, completion of permissive logic or proper indication of breaker position. Additionally, failure-of these W-2 cell switches could cause a delay in operator response. Consequently W-2 cell switch failure represents a significant deviation from performance and specifications and meets the. criteria for deportability pursuant to 10CFR50.55(e).
Lorrective Action TU Electric will replace the W-2 cell switches in the 480V switchgear for Units -1 and 2 prior to Unit I fuel load for Unit I end prior to Unit 2 fuel load for Unit 2.
In order to preclude recurrence, appropriate maintenance procedures will be revised to provide for continuity checks whenever a breaker is removed from its connected position.
Additionally, Westinghouse has recommended inspection
.of the W-2 cell switch internal structure every ten years.
Due to plant experience at CPSES which identified spring deformation at six to seven years, TU-Electric will revise the maintenance procedures to provide for inpsection of the W-2 cell switch internal structure every five years, while continuing Westinghouse recommended continuity checks. The appropriate maintenance procedure revisions will be completed prior to Unit 1 fuel load for Unit I and prior to Unit 2 fuel load for Unit 2.
Sincerely, 4Gb William J. Cahill, Jr.
WJH/vid c - Mr. R. D. Martin, Region IV Resident Inspectors, CPSES (3) l
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