Part 2 of 2 Parts (Please read Part 1 first)
One pipefitter involved in the 2021 incident was initially found to have an internal dose of nine hundred and sixty millirems and the second had an internal dose of seven hundred and eleven millirems.
The NRC mandates a limit of five thousand millirems per year for both external and internal radiation. EN sets a more conservative limit for exposure to two thousand millirems per year.
The radiation protection technician received an internal dose of fourteen millirem. Eighteen other workers had unintended uptakes of less than one millirem after walking past the area of airborne radioactive particles as they evacuated the room.
The updated NRC information claimed 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 the personal contamination monitors which were triggered. This indicated that there was radioactive material on or in the workers.
After multiple showers and scans of the personnel contamination monitors, EN confirmed that the pipefitters had internal uptake of radioactive materials. The two workers were sent to initiate the whole-body count process. Initial counts confirmed that they had inhaled or ingested cobalt 58 and cobalt 60 radionuclides. However, there was indication from inspections of the pipe that was cut that plutonium 239 and plutonium 240 contamination was possible in the incident. However, that information was not used to assess worker’s exposure.
According to the NRC report, EN’s procedures for internal dose assessment were incomplete, failed to provide clear direction and did not fully address all radionuclides that could have contaminated the pipefitters. Radiation 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 after the incident.
According to the most recent NRC inspection report, “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.” EN also failed to effectively take air samples in the workers’ breathing space during the incident.
According to the NRC report, the EN procedures were inadequate, but the EN did not have the equipment or personnel available to address the level of contamination and assess the dose within workers’ bodies.
EN said that they would provide a written reply to the NRC in response to notification of the preliminary white finding related to workers uptake of radioactive materials.
For the final white finding of the incident, EN Northwest will undergo a supplemental NRC inspection to demonstrate that the causes of the incident are understood and have been resolved.
EN said that no contamination left the building where employees were working during the incident or put the health and safety of the public at risk.
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.”