The Nuclear Regulatory Commission has planned an informational meeting for Tuesday on pressurized thermal shock – a potential threat to pressurized water reactors that the agency has indicated could force an early retirement for the Palisades nuclear plant.
Neutron radiation, thermal aging and load-cycle fatigue can change the properties of the metal forming reactor pressure vessels as they age, according to the International Atomic Energy Agency. Within PWRs, a very specific combination of circumstances could expose embrittled metal to thermal shock caused by the rapid introduction of cold water during emergency proceedures and rupture the vessel once it is repressurized.
International organizations and nuclear plant owners have studied reactors' effects on RPV metal since the 1960s, and NRC regulations require PWR licensees to submit analyses of their RPV material and its resistance to thermal shock. The agency will hold a meeting and webinar at 5 p.m., EST, Tuesday, on pressurized thermal shock and how it relates to the NRC's regulation of the Palisades plant. The WOOD TV station and other outlets reported that the NRC has notified Entergy that it must demonstrate by 2017 that Palisades' aging RPV can meet thermal shock requirements. In the unlikely event it can't, the plant would be required to shut down. An NRC spokesman told the station that there is no immediate safety concern at the plant.
Palisades operates a single 811 megawatt Combustion Engineering PWR that entered service in 1971, according to Entergy.