ML20066J087
| ML20066J087 | |
| Person / Time | |
|---|---|
| Site: | Zimmer |
| Issue date: | 11/08/1982 |
| From: | Borgmann E CINCINNATI GAS & ELECTRIC CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, QA-2107, NUDOCS 8211230440 | |
| Download: ML20066J087 (2) | |
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THE CINCINNATI GAS & ELECTRIC COMPANY C
l ClNCIN N ATI, OHIO 452ol November 8, 1982 QA-2107 E. A. BORGM ANN stNeon vect PassioENT U. S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137 Attention:
Mr. J. G. Keppler Regional Administrator RE:
WM. H. ZIMMER NUCLEAR POWER STATION UNIT 1 10CFR50.55(e) ITEM E-28, DEFICIENCY IN DG CONTROL LOGIC, DOCKET NO. 50-358, CO*.~STRUCTION PERMIT NO. CPPR-88 W.O. #57300, JOB E-5590, FILE E-28 Gcntlemen:
This letter constitutes an interim report concerning the subject deficiency reported under the requirements of 10CFR50.55(e). Our last report on this subject was submitted on September 30, 1982. This report stated that the deficiency was definitely reportable under 10CFR50.55(e).
The previous report described a sequence of cJonts which could lead to the paralleling of all three (3) emergency buses on the same diesel generator, sub-sequent overloading of that diesel generator, and a potential loss of an essential bus. The report also stated that the deficiency could be corrected by tripping the emergency diesel generator circuit breaker with an ESF actuation signal when the DG was operated in parallel with an offsite power source.
We have completed our engineering evaluation of this deficiency. The described sequence of events occurs because the emergency diesel generator energizes the in-coming potential transformers that supply voltage signals to the Essential Relay i
Panel (ERP). Consequently the ERP cannot determine that offsite power has been lost.
The deficiency will be corrected by tripping the diesel generator circuit breaker with an ESF actuation signal when the generator is operated in parallel with an onsite or offsite power source. This will de-energize the bus and allow the essen-tial relay panel to perform bus transfers, loadshedding and resequencing as designated.
The trip signal will be reset after a short time delay or when the offsite or onsite source circuit breaker opens.
The logic changes described above will be accomplished by modifying the diesel generator circuit breaker trip logic utilizing existing ERP output contacts and diesel generator auxiliary relays. An additional output relay will be required for each ERP. These modifications should be complete by June 1, 1983. Our final report on this matter will be submitted on or before June 15, 1983.
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Mr. J. G. Kepple:
Regional Administrator Region III November 8,1982 - QA-2107 Page 2 We trust that the above will be found acceptable as an interim report under 10CFR50.55(e).
Very truly yours, THE CINCINNATI GAS & ELECTRIC COMPANY
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By E. A. BORGIANN SENIOR VICE PRESIDENT WPC/csc cc: NRC Office of Inspection 6 Enforcement Washington, D.C.
20555 NRC Senior Resident Inspector ATTN:
W. F. Christianson Zimmer Project Inspector Region III