Improperly calibrated monitoring equipment at Entergy's Waterford 3 nuclear power plant could have low-balled the public health threat of radioactive gases released had there been an accident during three months in 2022, according to the federal Nuclear Regulatory Commission.
Entergy officials notified NRC inspectors of the problem during an Oct. 23 to Dec. 7 inspection of Waterford's emergency preparedness programs. Incorrect engineering conversion factors for measuring gases were loaded into the radiological dose assessment modeling software of two "wide range gas monitors" at the plant that are used in emergency responses, according to a Jan. 12 NRC letter.
The letter — from Mary Muessle, director of NRC's division of radiological safety and security, to John Ferrick, a vice president with Entergy Operations Inc. — said the errors resulted in readings that were 30.5% lower than the actual radiological conditions, which would have made public health and on-site dose calculations inaccurate.
The programming errors were corrected on Sept. 9.
Muessle said the monitoring issue is an apparent violation of NRC regulations, which is now being considered for "escalated enforcement" for "failure to maintain adequate methods for assessing potential consequences of a radiological emergency condition."
The violation is considered to be of low-to-moderate safety or security significance.
The NRC will complete a final evaluation in 90 days to determine whether fines or other actions are required, and Entergy was given an opportunity to provide its perspective during a conference or in writing.
Michael Bowling, director of communications for Entergy Nuclear, said Entergy will not request a regulatory conference over the potential violation.
"The issue had no actual consequences on safety, as stated in the NRC's report," Bowling said. "We appreciate the NRC's involvement in such issues, as they act to verify our actions are appropriate and ensure all factors have been considered."
"We are committed to keeping our plants, employees and communities safe and secure as we continue providing them with reliable clean energy," he said.
Waterford 3 is owned by Entergy Louisiana and operated by Entergy Nuclear, which also operates three other Entergy-owned nuclear plants in Louisiana, Mississippi and Texas. The plant's 1,152 maximum megawatt electricity production represents about 30% of Entergy Louisiana's total generation.
Waterford 3 was actually placed under increased oversight by the NRC in September because of another incident involving improper calibration of radiation monitors that could have triggered unnecessary evacuations.
It's unclear whether last year's inspection was added as a result of the earlier problem, where NRC found radiation monitors at the plant were being calibrated improperly between January 2011 and February 2022.
The agency said that despite numerous opportunities to correct the errors, they remained in place until discovered by Waterford workers at the beginning of 2022. During an NRC inspection between April 24 and May 17, 2022, inspectors found the calibration errors resulted in readings that were 69% to 76% greater than actual potential radiation levels.
During an accident involving a release of radiation, the inaccurate readings could result in a "general emergency" declaration, which could have triggered evacuations, according to the inspection report.
NRC issued Entergy a preliminary green, non-cited violation, rating in February when that problem was initially identified during an earlier inspection, but upgraded it to a white finding in September.