KENNEWICK — Energy Northwest failed to correctly measure the exposure of workers who inhaled or ingested radioactive material during an incident at the Northwest’s only commercial nuclear power plant, said the Nuclear Regulatory Commission.
On the night shift during the spring refueling and maintenance outage two years ago, some workers received unexpected and significant exposure to radiation, according to the initial report by the NRC.
The NRC issued a “white finding” last week and said it is considering issuing a second white finding after workers were exposed to radiation May 28, 2021, at Energy Northwest’s Columbia Generating Station nuclear power plant, according to documents made public Monday.
A white finding, the second lowest on NRC’s four-step color scale, has low to moderate safety significance and can lead to an additional NRC inspection to make sure issues have been corrected.
The notice of the first white finding was for three violations in the incident — failure to the control the concentration of radiation material in the air, failure to control the activities in a high radiation area and failure to survey areas to evaluate the extent of radiation levels.
But while investigating the incident at the plant near Richland, the NRC also began questioning whether Energy Northwest correctly measured the internal radioactive exposure of the workers.
Because of additional concerns raised at a March 1, 2022, regulatory conference with Energy Northwest about the 2021 incident, the NRC also on Thursday issued a preliminary white finding for Energy Northwest’s assessment of the workers’ uptake of radioactive material.
Energy Northwest failed in the 2021 incident to take timely measurements of airborne concentrations of radioactive materials in work areas, to collect as many urine and fecal samples as were needed to provide good results and to evaluate certain isotopes in workers’ bodies, the most recent NRC inspection report said.
“These failures resulted in an inability for the licensee (Energy Northwest) to properly assess the dose accrued by the pipefitters,” two of the workers in the incident, the report concluded.
The exposures were within the regulatory limits for annual radiation exposure and Energy Northwest’s administrative limits but “it is unacceptable for workers at Columbia Generating Station to receive unanticipated radiological dose of any amount,” said Bob Schuetz, chief executive of Energy Northwest, in a statement on Monday.
“We take this event very seriously and are disappointed with the circumstances that led to these results,” he said.
NRC account of radiation release
According to the initial NRC account of the incident, radiation workers and pipefitters on the night shift May 28, 2021, were preparing for welding on piping of the highly contaminated reactor water cleanup heat exchanger.
After the pre-job briefing, a radiation protection technician was unable to get on the work platform attached to scaffolding and left to find another technician to fill in. The technician who filled in had not attended the briefing and arrived after workers already were cutting into a pipe.
The work on the pipe, including grinding, required using an enclosure glove bag to contain any radioactive particles that might become airborne.
But workers used the wrong glove bag inlet attachment, and the glove bag collapsed when a vacuum system was turned on. Workers turned off the vacuum system, which allowed airborne radioactivity to collect and escape when the glove bag was removed, according to the inspection report.
A radiation protection technician watching work on video surveillance cameras spotted the issue and within 30 seconds was in the room and had ordered work stopped.
As radioactive contamination was found on the faces of two pipefitters, 20 more workers in the room were evacuated.
One pipefitter initially was found to have an internal dose of 961 millirem and the second had an internal dose of 711 millirem.
The NRC limits exposure to 5,000 millirem per year for both external and internal radiation, and Energy Northwest sets a more conservative limit of 2,000 millirem.
One radiation protection technician received an internal dose of 14 millirem. Eighteen other workers had unintended uptakes of less than 1 millirem after passing by the area of the airborne radioactive particles as they evacuated the room.
Radiation readings ‘off-scale high’
The updated NRC information says that as the two pipefitters left the heat exchanger room, they were frisked by radiation protection staff “and the instrument readings went off-scale high.”
They were then escorted to personnel contamination monitors, which alarmed, indicating there was radioactive material on or in the workers.
After multiple showers and scans on the personnel contamination monitors, Energy Northwest confirmed they had internal uptakes.
The two workers were sent to initiate the whole-body count process, with initial counts confirming they had inhaled or ingested cobalt 58 and cobalt 60 radionuclides.
However, there was indication from checking the pipe that was cut that plutonium 239 and plutonium 240 contamination was possible in the incident, but that information was not used to assess workers.
Energy Northwest’s procedures for internal dose assessment were incomplete, failed to provide clear directions and did not fully address all radionuclides that could have contaminated the workers, according to the NRC report.
Dose is a measure of the amount of radiation absorbed that accounts for the type of radiation and its effects on particular organs.
The two pipefitters had their urine tested only once and no fecal samples were collected.
“In conclusion, not only did the licensee (Energy Northwest) fail to implement the most appropriate sampling methods to detect the level of hard-to-detect radionuclides from the intake, including alpha emitters, but they did not take any additional samples to suitably establish trends and elimination rates of these radionuclides,” according to the most recent NRC inspection report.
Energy Northwest also failed to effectively take air samples in the workers’ breathing space during the incident, the NRC said.
Not only were procedures inadequate, but Energy Northwest did not have the equipment or personnel available to address the level of contamination and assess the dose within workers bodies, according to the NRC report.
NRC inspection planned
Energy Northwest plans to provide a written reply to the NRC in response to notification of the preliminary white finding related to workers’ uptake of radioactive material.
For the final white finding from the incident, Energy Northwest will undergo a supplemental NRC inspection to demonstrate the causes of the incident are understood and have been resolved.
No contamination left the building where employees were working during the incident or put the health and safety of the public at risk, Energy Northwest said.
“In the nuclear industry, safety is our top priority, and we are held to the highest standards,” Schuetz said. “In this instance, we did not live up to that standard, and we will work with the NRC to complete the follow-up inspection to be able to return Columbia Generating Station to top industry performance.”
