The Nuclear Regulatory Commission is conducting an investigation at Browns Ferry nuclear power plant, located near Athens and operated by the Tennessee Valley Authority, after an incident in which a diver received a dose rate alarm during underwater work on November 7.
A diver was working on an underwater steam dryer system when he received an electronic dose rate alarm after approaching the equipment pit wall. After receiving the alarm, the diver followed protocol and left the pit immediately. The dose did not exceed the regulatory limits.
According to TVA, the dose rate alarm monitors a person's amount of radiation they are exposed to. At a plant like Browns Ferry, workers are expected to be exposed to a certain amount of radiation. In this incident, however, the rate alarm was triggered because the diver was exposed to a higher than expected radiation level.
It was later determined that a basket of used filters had previously been moved from a spent fuel pool to nearby the equipment wall, which had not been communicated to workers in the next shift.
TVA says investigators are looking at the basket of used filters that were moved, which could have triggered the alarm to a higher than expected dose rate, since the workers didn't know the filters were there.
The NCR's inspection team is working to identify everything surrounding the event. This is expected to take several days and a report documenting the results should be issued within 45 days of the investigation's completion.
TVA's statement on the Browns Ferry inspection is below:
"TVA Nuclear is aware of this special inspection by the NRC and is fully cooperating with inspectors. We are independently performing a detailed review and causal analysis of the issue. We do know at this point that there was no impact to the health and safety of the diver, that all safety equipment worked as designed and there were no safety concerns for the public or plant personnel. TVA is committed to the safe operation of its nuclear facilities."