David Lochbaum, the Union of Concerned Scientists' Nuclear Safety Project Director, listed a "near-miss" at Entergy's River Bend atomic reactor, a General Electric Mark III Boiling Water Reactor, amongst his list of the 14 near-misses of 2012 in the U.S. nuclear power industry. He summarized the near-miss this way:
"The operators manually shut down the reactor on May 24 after an electrical fault on the motor of a feedwater pump caused it to stop running. A failed relay prevented the electrical breaker for the motor from opening to isolate the electrical fault. The fault propagated through the electrical distribution system, causing the breaker supplying power to the 13,800 volt electrical bus to open. Due to another electrical cable problem on May 21, all of the plant’s circulating water pumps and non-emergency cooling water pumps were being powered from this single electrical bus. Its loss caused the plant’s normal heat sink to be lost and stopped the supply of cooling water to equipment in the turbine building and to some emergency equipment."
Lochbaum explained that the incident prompted an NRC AIT, a U.S. Nuclear Regulatory Commission Augmented Inspection Team, signifying a one hundred fold increase in risk of reactor core damage, thus amongst the very most serious near-misses of 2012.
Lochbaum's summary is contained in his current annual report on U.S. atomic reactor near-misses, and NRC's safety regulatory performance (or lack thereof), entitled "Tolerating the Intolerable."