TXX-4109, Deficiency Rept Re Failed Inverters in Nsss.Caused by Grounded Secondary Winding of Inverter Ferroresonant Output Transformers.Transformers Will Be Returned to Manufacturer for Repair
| ML20080P440 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/13/1984 |
| From: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| TXX-4109, NUDOCS 8402220545 | |
| Download: ML20080P440 (2) | |
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0, TEXAS UTILITIES GENERATING COMPANY M KY WAY TOWE N
- 400 NORTIE OI.IVE MTH EET, I..ll. M1
- IDA P.I.AM, TEX AM 7320 8 R. J. GARY February 13, 1984 TXX-4109 Mr. E. H. Johnson, Chief Reactor Project Branch 1 U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement 611 Ryan Plaza Drive, Suite 1000 Docket Nos.:
50-445 Ar1ington, TX 76012 50-446 COMANCHE PEAK STEAM ELECTRIC STATION FERRORES0NANT TRANSFORMERS QA FILE: CP-84-04, SDAR-128 FILE NO.:
10110
Dear Mr. Johnson:
In accordance with 10CFR50.55(e), we are submitting the enclosed report of actions taken to correct a deficiency regarding inverters in the NSSS which have experienced failure.
Supporting documentation is available at the CPSES site for your Inspectors review.
Very truly yours, RJG:In cc:
NRC Region IV - (0 + 1 copy)
Director, Inspection & Enforcement (15 copies)
U.S. Nuclear Regulatory Commission Washington, DC 20555 8402220545 840213 PDR ADOCK 05000445
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PDR L
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A DEVENION OF TEKAN l'TILITIEN ELECTNit' COMi%NY
TXX-4109 February 13, 1984 ATTACHMENT Ferroresonant Transformers Description Within four (4) months of initial startup testing, three (3) inverters in the NSSS system experienced failure.
Initial loading on the inverters was 40 percent to 50 percent of design load.
The failures have been attributed to a grounded secondary winding of the inverter ferroresonant
-output transformers.
A fault analysis performed by the manufacturer (GE) indicates failure is due to shift and vibration of small parts of laminations which compose the center core leg of the transformer. The vibration abrades the coil insulation and, in time, penetrates the insulation connecting the coil and core. Each transformer failure is attributed to insufficient securing of the center leg.
The inverters supply power to the NSSS instrumentation buses.
Site engineering has determined the issue is generic to all ferroresonant transformers.
Safety Analysis In the event the defect had not been detected, the inverters could fail in operation rendering NSSS plant status or monitoring systems inoperable.
Corrective Action-The transformers will be returned to the supplier (Westinghouse) for repair by the manufacturer. Repair will consist of:
a.
Replacing the insulation with material more resistant to
- abrasion, b.
Treating the insulation with hard bonding material, c.
Incorporating improved mechanical wedging for the center leg, and d.
Hi-pot production tests at 4000V (vs. 2500V) for assurance of dielectric integrity.
Reinstallation of the transformers will be completed no later than thirty (30) days prior to fuel load.
-.-