A north Alabama nuclear plant is facing investigation by the Nuclear Regulatory Commission after a high dosage of radiation was discovered in water in a plant equipment pit.

The NRC announced Wednesday has initiated a “special investigation” at Browns Ferry Nuclear Plant near Huntsville " to determine how and why a diver received a dose rate alarm during underwater work in the Unit 1 equipment pit."

“On Nov. 7, a diver working on an underwater steam dryer system received an electronic dose rate alarm when he approached the equipment pit wall to manipulate a cable,” the NRC said in its announcement. “Upon receiving the alarm, the diver immediately left the pit and his unintended dose did not exceed regulatory limits. The licensee later determined that a basket of used filters had been moved from the spent fuel pool into a position near the equipment wall and this was not communicated to the next shift.”

The investigation is expected to take several days, the NRC said, and a report on the probe is expected to be released within 45 days of completion of the investigation.

“NRC’s two-person inspection team will identify the circumstances surrounding the event, review the licensee’s immediate response to the alarm, evaluate their corrective actions and causal analysis, and assess the program for diving, work control, radiological surveys and movement of highly radioactive material,” the NRC said.

In a statement to AL.com, TVA said there was no danger to the public and the federal utility is cooperating with the NRC.

“TVA Nuclear is aware of this special inspection by the NRC and is fully cooperating with inspectors," spokesman Scott Fiedler said. "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.”

The plant, located outside of Athens in Limestone County, has had a history of issues.

In 2011, the plant received a “red finding” from the NRC – one grade away from a shutdown. In 2015, the NRC restored Browns Ferry to a “green finding” after past issues were addressed.