Today’s NRC Event Reports included these two:
1. The Davis Besse nuclear power plant in Ohio reported that the reactor lost all emergency feedwater service for about two minutes yesterday afternoon. More disturbing than the incident is the cause: While testing fire detection systems, a technician used a walkie-talkie in the vicinity of the Auxiliary Shutdown Panel. This resulted in Control Room alarms sounding.
Subsequent investigation showed that the interference had caused brief outages to all emergency feed water, a situation which resulted in a “loss of safety function for equipment needed to (A) shut down the reactor and maintain it in a safe shutdown condition and to (B) remove residual heat.”
Corrective action to prevent a repeat of the incident consisted of posting a new sign: “(A) sign (was) placed on the Auxiliary Shutdown Panel Room door stating that no radio usage is permitted inside the room.”
If there is one nuclear reactor where you particularly want all the safety systems to work all the time, it is Davis Besse. The plant is about to install its third reactor vessel head. The first one had corrosion that left only about 1/16 inch of metal remaining in one spot. Had the corrosion breached the reactor head, the result would have been a major radioactive leak into the containment building. The second reactor head developed cracks. Davis Besse has been given till next year to put on the third reactor vessel head, which it purchased from a never built Illinois plant.
2. Operators of the Susquehanna Unit 1 reactor in Pennsylvania begain a slow shutdown due to a problem with the High Pressure Coolant Injection (HPCI) system. The HPCI was declared inoperable due to a suspected steam leak. The plant entered a Technical Specification Required Shutdown, a step below a reactor scram, or emergency shutdown. As of this morning’s NRC Reactor Status report, Susquehanna 1 is down to 20 per cent power.