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NUCLEAR REGULATORY COMMISSION AE0D/E108 r.
p-WASHINGTON. D. C. 20555 k,,, /
APR 211981 y
This.3s an_ioternal, pre-decisional document not necessarily representing a position of AE0D or NRC.
MEMORANDUM FOR:
File
^7 y'O5 FROM:
M. Chiramal 2./
Office 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 "Transfomer 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 desigr. 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.
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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 cnd 27-2, however, are not designated Class 1E 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 licensee 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 ourselves informed of the resolution of the, design problem, we do not anticipate any further AE0D action.
Matthew Chiramal Office for Analysis and Evaluation of Operational Data gg
Attachment:
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BLE' 3CC:JRRENCC - elHILE PERF3RHI NG A R(LAY TRIP PROCEDURE, THE FCLL0 dup PE9 3 E IDENTIFIED THAT T'IE LOCK 0JT UNDERVOLTAGE RELAYS FOR THE MC 2515 OFFSITE? FEE 0 530JLD NOT OPERATE.
THESE RELAYS Allan THE EMER-TESELS TO TIE INT 3 THE EMERGENCY BUSES.
THE RELAYS WERE Y EXERCISED AND TESTED SATISFACTORILY.
UNIT 1 IS CURRENTLY FUELING DTdAGE.
UNIT 2 RELAYS WILL BE TESTED TODAY.
THE E'IS TNVESTIGATING THE RELAY FAILURE.
REPORT DUE 4/20, i
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