Two items from this morning’s NRC Event Reports:
1. Just after 4 pm yesterday afternoon, NextEra Energy declared the ‘A’ River Water Supply inoperable at the Duane Arnold nuclear power plant in Iowa. Because the ‘B’ River Water Supply for the reactor was inoperable at the time due to maintenance, the plant entered a Technical Specification condition, calling for a slow shutdown of the reactor over the next twelve hours. Before that could be accomplished, however, repairs to the second system were completed, and the Tech Specification condition was cancelled.
What is disturbing about the incident is the reason for the ‘A’ system shutdown. Operators discovered that a controller in the system was installed backwards. According to the report: “This would have closed the HVAC intake dampers on high temperature instead of opening them.”
The reactor at Duane Arnold is a General Electric Mark I boiling water reactor, like a couple of the reactors that failed at Fukushima. Duane Arnold came online in 1974, which raises the question: How long has the part been installed backwards?
2. At about the same time yesterday afternoon, operators at the Pilgrim nuclear power plant in Massachusetts were having problems with another GE Mark I reactor. The High Pressure Coolant Injection system (HPCI) for the Unit 1 reactor was declared inoperable. The reactor had been undergoing maintenance to the HPCI. Following the procedure, operators received an indication that a valve that should have been closed was only partially closed. The report says that the unit is currently in a Limited Condition for Operation, but this morning’s Reactor Status Report says that the reactor is still operating at 100 per cent power.