A May 2021 radiation exposure of 22 workers resulted in a federal preliminary finding of a low-to-moderate safety problem for the Columbia Generating Station in Richland, Washington, the Nuclear Regulatory Commission said recently.
The Nuclear Regulatory Commission (NRC) has four levels of classifications for safety problems. Green means a finding of very low safety significance . White means a finding of low to moderate safety significance. Yellow translates to a substantial safety problem. Red indicates a great safety problem
On Jan. 13, the agency issued a preliminary finding of “white” to Columbia Generating Station owner Energy Northwest.
The NRC has scheduled a teleconference with Energy Northwest officials at 7 a.m. Pacific Time on March 1 to discuss the incident. The public can listen to the meeting and ask questions by calling 800-857-5003 and entering passcode 5204033#.
In the Jan. 13 letter and an accompanying report, the NRC wrote that Energy Northwest workers did not follow written procedures and radiological rules in a May 28, 2021 pipe-welding project during a routine maintenance shutdown of the reactor. That resulted in radioactive particles becoming airborne. The welding work was on a highly radioactive reactor water cleanup heat exchanger.
Of the 22 exposed workers, one received a committed effective dose equivalent of 961 millirems, while another received 711 millirems, according the NRC report. Sixteen received doses of 1 millirem or less, most while passing the contaminated area. The NRC set a maximum exposure limit of 5,000 millirems per year, while Energy Northwest works with a 2,000 millirems limit.
The report said one radiation protection technician attended a formal safety briefing and was assigned to provide non-stop “line-of-sight job coverage” of the welding in the heat exchanger room. He could not fit on a work area platform attached to some scaffolding so he left his post to get another technician to replace him. The second radiation protection technician had not attended the work briefing, which violated safety procedures.
Meanwhile, workers on the platform had already begun cutting into a pipe before the second radiation protection technician showed up. A glovebox was used to keep radioactive particles from escaping.
At a remote monitoring station about 40 feet away, a radiation protection supervisor — who was not required to provide continuous visual supervision — saw problems with part of the glovebox, resulting in radioactive particles escaping. He went to the work platform and stopped the cutting.
A follow-up radiological inspection found contamination on the workers. If the cutting work continued a few more minutes, the exposures would’ve been significantly worse, the report said.
