Switchyard fire posed no radiation hazard
– By Stephen Heiser –
Crews at the Davis-Besse Nuclear Power Plant in Carroll Township are working to fix a backup power source after a small fire last Thursday. According to a spokeswoman with the Nuclear Regulatory Commission, the minor fire, which took place in the switchyard, took one of the two backup power systems off line. The plant was working on normal power at the time of the fire, but two backup systems need to be ready to operate at all times due to federal regulations.
According to a FirstEnergy spokesperson there was never any danger to the public, and no radiation was ever released.
NRC REPORT FOLLOWS:
DISCOVERY OF AN AFTER-THE-FACT ALERT DUE TO CATASTROPHIC FAILURE OF CCPD
"A transitory ALERT [condition was determined to have existed] based on Emergency Action Level 7.D.2 – 'Onsite Explosion Affecting Plant Operation'. At time 0049 on 06/25/09 a catastrophic failure-explosion of the Constant Current Potential Device (CCPD) on 'J' Bus near Air Circuit Breaker (ACB) 34563 resulted in a loss of switchyard 345 KV Bus 'J'. This event de-energized Startup Transformer 01 which is a tie from offsite sources to the Unit 13.8 KV Busses. The unit entered [Technical Specification] LCO 3.8.1, Condition A [due to the loss of one offsite power source]. The Unit remains stable and in operation at 100% RTP [reactor thermal power]. A problem solving decision making team is working on [the] troubleshooting/repair/restoration activities. This event did not impact any plant safety systems or result in any release of radioactive material."
Failure of the CCPD caused automatic opening of the breakers on both sides of the 'J' bus which was configured as part of a switchyard ring bus at the time of the event. This resulted in the loss of one of the offsite power ties. However, startup Transformer 02 is still energized from offsite power and remains available for plant operations. Other than the de-energized startup transformer, onsite electrical configurations are normal including availability of emergency diesel generators. The licensee is in a 72 hour LCO per Tech Spec 3.8.1, Condition A, to restore the lost offsite power source. The licensee is inspecting the switchyard for collateral damage to other equipment from the failure of the CCPD. The licensee believes the CCPD failure is likely a result of equipment failure and not the result of any equipment tampering.
The licensee stated that initially, the severity of the CCPD failure was not recognized because of the night time conditions and minimal lighting in the area. After daylight examination of the location of the event, it was determined that the failure of the CCPD should have been classified as an explosion affecting plant operation under EAL 7.D.2. Consequently, the licensee made the after-the-fact declaration.
Licensee has notified the NRC Resident Inspector, and will be notifying State and local authorities.