ML20027C009
| ML20027C009 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/21/1981 |
| From: | Chiramal M NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | |
| References | |
| TASK-AE, TASK-E108 AEOD-E108, NUDOCS 8210120171 | |
| Download: ML20027C009 (3) | |
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g NUCLEAR REGULATORY COMMISSION AE0D/E108
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E WASHINGTON, D. C. 20555 This is an internal, pre-a.,
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APR 211981 decisional document not necessarily representing a position of AE00 or NRC.
MEMORANDUM FOR: File
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fOgO,6 FROM:
M. Chiramal 0 fice for Analysis and Evaluation of Operational Data
SUBJECT:
HATCH UNITS 1 and 2 - ALTERNATE OFFSITE SOURCE INTERLOCK WITH EMERGENCY DIESEL GENERATORS
Reference:
(1) IE Daily Report dated April 6, 1981 The licensee, while performing a relay trip procedure at Hatch 1, identified that the undervoltage relays of the second offsite source would not operate.
The relays are designated " Transformer 1C UV relays 27-1 and 27-2."
(see attached logic diagram). Transformer 1C is the alternate offsite source to the safety-related buses.
The design of the station safety-related electrical system is such that on loss of the primary offsite source (monitored by UV relays 27-3,.27-4, 27-5, and 27-6 on each safety bus) the diesel generators are started and the safety buses seek the alternate offsite source -- transformer 1C.
If this offsite source is unavailable (as seen by the operation of UV relays 27-1 and 27-2), then the DG breakers are closed to energize the safety buses.
The UV relays 27-3 through 27-6 that monitor the voltage of each safety bus are designated as Class lE equipment -- a set of four is provided for each bus.
The UV relays 27-1 and 27-2, however, are not designated Class lE and only one pair is provided for all the safety buses. On April 6, 1981 during the trip procedure, relays 27-1 and 27-2 did not operate, thus preventing the closure of all the DG breakers on Unit 1.
The design is the same for Unit 2.
The li; see will be proposing a design modification to correct the problem of the non-Class lE interlock that prevents the automatic operation of safety systems. ORAB/NRR is presently pursuing this matter. Other than keeping ou selves informed of the resolution of the design problem, we do not antic' ate any further AE0D action.
Matthew Chiramal Office for Analysis and Evaluation of Operational Data
Attachment:
As stated cc w/ attachment:
CMichelson, AE00 CHeltemes, AE00 FAshe, AE00 8210120171 810421 PDR ADOCK 05000321 S
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..s 3LE 3CC:JRRENCE - elHILE PERF 3RMING A HELAY TRIP PROCEDURE, THE FULL 0 dup PER E IDENTIFIED THAT T'IE LOCK 0JT U'dDERVOLT AGE RELAYS FOR THE MC 2515.
OFFSITE; FEE 0 *l3JLD NOT OPERATE.
THESE RELAYS ALLOn THE ENER-IESELS TO TIE 19T3 IHE EPERGENCY HUSES.
THE RELAYS WERE Y EXERCISED AND TESTED SATISFACTORTLY.
UNIT 1 IS CURRENTLY FUELI.NG OTJAGE.
UNIT 2 RELAYS hill BE TESTED TODAY, THE E IS TWESTIGATING THE RELAY F AILURE.
REPORT DUE 4/20.
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