Entergy's River Bend nuclear power plant near St. Francisville sits next to the Mississippi River for a reason.
The Big Muddy's waters are used to keep the uranium reactor core of the 974-megawatt power plant cool. But the big facility in West Feliciana Parish north of Baton Rouge also has a storage tank holding hundreds of thousands of gallons of water in case an accident blocks access to the river.
Under federal rules and River Bend's original license from 1985, Entergy must maintain an emergency supply in the tank large enough to keep the core cool for at least 30 days, but the power utility is expected to seek an amendment by the end of the year to its licensing papers to cut that minimum by two days.
U.S. Nuclear Regulatory Commission officials said Entergy is expected to seek the change after they cited the company for trying improperly to credit operators' refilling the tank at day 28 to maintain that 30-day capacity.
The breakdown is one of eight the commission has cited Entergy with since January 2022. They are prompting a follow-up federal inspection of the nuclear power plant between Oct. 7 and 11, agency officials said.
NRC officials said the change to the so-called "heat sink" minimum supply and other violations have "low level safety significance" and never posed an actual danger to the public or power plant security.
"There were plan documents that needed to be updated that were not or changes were made in plant procedures before consulting with us as required," said Victor Dricks, NRC spokesman. "In this upcoming inspection, Entergy is looking and has looked at how they missed probably notifying us of these changes they made and we are evaluating their corrective actions to ensure they are adequate."
NRC had previously agreed to push back this inspection of these lower level issues to allow Entergy to complete other more pressing upgrades that also needed agency inspection.
The inspection planned next month came to light in a letter dated Sept. 16 that NRC sent to Entergy requesting documents to prepare for the visit.
Michael Bowling, an Entergy spokesman, said the violations fall in the lowest of NRC's significance levels and reflected "discrepancies related to how we captured technical detail changes in our official documents, including procedures and technical specifications."
He said those violations have been addressed and the inspection will allow NRC to review Entergy's work.
"We take safety, security and adherence to process extremely seriously," Bowling said.
A report about a Sept. 30, 2023, NRC inspection indicates questions about the capacity of the backup water supply at River Bend have been an issue for regulators since late 2011. Entergy had considered a license amendment in 2014 only to withdraw it due to agency concerns.
NRC officials said Entergy has never operated the reactor with less than a 30-day water capacity but had been doing so by relying on operators to refill the tank when the water inventory ran low.
River Bend has been citied with low-level violations on three prior occasions for trying to credit operator actions, they said. The supply is supposed to stand for 30 days without manual supplement.
In March, testing during refueling of the River Bend reactor found that leaks in the standby system providing reactor cooling water was significant enough to render the heat sink system inoperable, in part because it would require additional water.
Jeffrey Josey, the NRC branch chief who oversees River Bend, said the kind of change Entergy is expected to seek has been granted to nuclear power plants before because maintaining the 30-day supply can be hard. But the utility must demonstrate the change won't affect the safety of the reactor core.
Entergy officials pointed out that the longstanding issues driving the coming license amendment for the backup cooling water system revolve around documenting whether the water supply included this so-called manual "make-up" capability to restock the plant's backup tank.
"The make-up capability meant we would be able to supply cooling water, but several days would be covered under a different method," he said.
Bowling added that since receiving the NRC letter this month, River Bend has added layers of safety by "raising water levels in the minimum standby cooling tower, establishing additional methods to provide make-up water and ensuring we’ve reduced or eliminated unnecessary heat load."
Some of the other violations cited in the letter appeared to be basic data input errors, NRC officials said.
Edwin Lyman, a nuclear power and safety expert with the Union of Concerned Scientists watchdog group, said plants not meeting standards and specifications can lead to them being "caught short" if something does happen.
"They make it seem like it's just paperwork, but the fundamental basis for the safety of these plants is in the paperwork," he said.