PNO-III-85-071A, circuitry Mods to Plant Transformers Completed & Successfully Tested on 850819.Mods Instituted Due to Failure in Switching Mechanism in Auxiliary Main Station Transformer
| ML20137E986 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/20/1985 |
| From: | Harrison J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| References | |
| PNO-III-85-071A, PNO-III-85-71A, NUDOCS 8508260115 | |
| Download: ML20137E986 (1) | |
bq PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-85-71A Date August 20, 1985 Q}/.
M This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance.
The information is as initially received without veri-fication or evaluation, and is basically all that is known by the staff on this date.
Facility: Commonwealth Edison Company Licensee Emergency Classification:
Dresden Unit 2 Notification of an Unusual Event Morris, IL 60450 XX Alert Site Area Emergency Docket No: 50-237 General Emergency Not Applicable Subgct:
LOSS OF 0FF-SITE POWER (UPDATE)
The licensee has completed circuitry modifications for the Unit 2 transformers. This will assure proper transfer of auxiliary power from off-site to on-site sources to preclude a similar loss of off-site power incident like the one which occurred August 16, 1985.
The licensee determined that the incident occurred because of a failure in the switching mechanism from the Unit 2 auxiliary transformer to the Unit 2 main station transformer.
The circuitry modification was successfully tested on August 19, 1985. The licensee plans to restart the reactor on August 20, following additional maintenance activities.
Unit 3 continues to operate near full power. The licensee has taken steps to provide additional auxiliary power to Unit 3, and has committed to completing transformer circuit modifications on Unit 3 in the same manner as it did on Unit 2.
These modifications will be accomplish'ed during the October refueling outage or sooner if the unit is shut down for more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
During the event, trace amounts of radioactive material were vented to the environment from the isolation condenser, which was used to cool the reactor during the loss of off-site po.Or incident. No contamination was found off-site, and only a trace amount was found on a 10 by 10 foot slab of concrete directly beneath the vent.
The resident inspectors and a Region III inspector monitored the licensee's corrective actions and witnessed the successful test of the transformer circuit modification.
The State of Illinois will be notified.
This information is current as of 9:30 a.m., August 20, 1985.
CONTACT:
J.
Harrison N.
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