US NRC Launches Special Inspection
by Elaine Hiruo
Washington -- The US Nuclear Regulatory Commission launched a special inspection Monday into three incidents during the extended outage at the Columbia plant outside Richland, Washington, this summer during which operators inadvertently drained reactor coolant from the reactor vessel.
NRC said that the three events at the Energy Northwest station involved "problems with the alignment of valves on the reactor coolant system and level instrumentation."
The three-inspector team will also review two other events that involved a "temporary loss of shutdown cooling due to an electrical malfunction and the unexpected insertion of a control rod into the reactor core during a scheduled test," the agency said.
NRC spokesman Victor Dricks said Monday that on April 11 the reactor vessel was overfilled with water as crews prepared to remove the reactor vessel head and that misaligned valves resulted in 4,000 gallons being drained from the vessel.
On July 29, three feet of water was inadvertently drained from the reactor vessel, Dricks said. He added that there still was 20 feet of water above the fuel in the fuel in the core.
On September 10, while crews were switching from one train of a residual heat removal system to another, a misaligned valve resulted in 260 gallons being drained from the reactor vessel in 20 seconds, Dricks said. There still was more than 19 feet of water above the fuel, he said.
"All of these events had very low risk significance because the reactor was in a safe shutdown condition," NRC region administrator Elmo Collins said in the agency statement. "But they all appear to have involved poor operator controls and warrant close examination."
Columbia shut April 2 for what was scheduled to be an 80-day refueling and maintenance outage. It exited the outage September 20. NRC reported Monday that the 1,173-MW unit was at 14% power.
Energy Northwest spokesman John Dobken earlier this month attributed the extended down time to the amount of work involved in replacing the plant's main condenser, which converts steam leaving the turbines into water for reuse.
It will take the NRC team about a week to complete the inspection, Dricks said. The team will submit a report on its findings within 45 days of completing its inspection, according to NRC.
learn more on topics covered in the film
see the video
read the script
learn the songs