NRC Event Reports for the long Presidents Day weekend included a slew of reactor problems:
1. Early Friday morning, technicians at Calvert Cliffs Unit 2 discovered what they terms an ‘inactive’ boric acid leak on a heater pipe in the reactor building. Operators are still investigating the problem.
2. Later on Friday morning, operators at Comanche Peak Unit 2 declared a Notice of Unusual Event (NOUE) due to excessive leaking from a charging system. The valve was isolated and the NOUE was terminted about four hours later. Repairs to the malfunctioning valve are being planned.
3. Early Saturday morning, workers at the Nine Mile Point reactor in New York were testing the Unit 1 Plant Process Computer. After the computer was tested and brought back into service, the Safety Parameter Display System (SPDS) failed, resulting in annunciator alarms in the Control Room. During the outage, plant operators say that they had “non-computer based emergency assessment capability.” (Dials and meters, I guess.) An additional operator was called in while the Process Computer was on the fritz. The SPDS was brought back into service after about four hours.
4. Saturday evening, the Palisades nuclear power plant in Michigan inadvertently released about 17 gallons of sodium bisulfate into Lake Michigan. Sodium bisulfite is commonly added to large piping systems to prevent corrosion. (Thanks, Wikipedia.)
5. Pilgrim Unit 1 in Massachusetts began a Limiting Condition of Operation early Sunday morning following the discovery of intrusion of salt water into the Reactor Building Closed Cooling Water system. As of Tuesday morning, the reactor was at 0 per cent power, and the cause of the leak is under investigation.
The problems for Pilgrim’s Unit 1 weren’t over, however. As the reactor was brought to zero power and the control rods were inserted, a low water signal was received and the Reactor Protection System automatically activated. It is unclear why this happened.
6. Also on Sunday morning, the Fitzpatrick and Nine Mile Point nuclear power plants in New York reported the loss of Tone Alert Radio capabilities. Nine Mile Point’s Event Report said: “The loss of the Tone Alert System constitutes a significant loss of Emergency Off-Site Communications capability.” The system was restored after about three hours.
7. And finally, the Emergency Diesel Generators for Units 1 & 3 at the Palo Verde nuclear plant in Arizona activated as the result of undervoltage to the reactors’ busses. An investigation found damage to common cabling providing outside power to the units. Apparently, the only thing that kept Unit 2 from being affected was that the generators were already out of service.