The U.S. Nuclear Regulatory Commission (NRC) said on Monday that it has launched a special investigation into the circumstances that led to a recent shutdown of the Callaway Nuclear Station near Fulton, Missouri, after the failure of three control valves.
The report said that on Aug. 11 during a planned startup, the plant, operated by Ameren, behaved normally until operators attempted to start motor-driven water pumps, when control valves failed to operate. The NRC said three out of four valves failed to operate. The valves regulate water flow into the steam generators.
“The purpose of this special inspection is to better understand the circumstances surrounding the valve failures, determine if the licensee’s extent-of-condition review was sufficiently comprehensive and review the licensee’s corrective actions to ensure that the causes of the failures have been effectively addressed,” NRC Region IV Administrator Marc Dapas said.
The NRC said circuitry in the valves had been modified in 2014 and that this is thought to have created a flaw in the valves’ operability.
Over a week-long period, NRC inspectors will be evaluating the facility’s maintenance, testing practices, the design changes to the valves and what corrective actions are needed in relations to this specific issue.
