Inspections during a refueling outage have turned up flaws in the housing of control rod drive mechanisms at the Palisades nuclear plant.
They were not through-wall, and no leakage was found. Nonetheless, 17 of 45 CRDM housings showed flaws that exceeded the acceptance criteria of ASME section XI, IWB-3600, according to a report filed with the Nuclear Regulatory Commission. Replacement or repairs are in progress, according to the report.
Entergy-operated Palisades last experienced problems with CRDM housings in 2012, when a crack about 1/8 inch long caused a coolant leak that required the reactor to shut down. According to an NRC report at the time, the plant between Chicago and Grand Rapids, Mich., concluded the leak was caused by a type of stress corrosion cracking that occurs under certain water chemistry and physical conditions. The Combustion Engineering pressurized water reactor also experienced a similar leak in 2001.