A spokeswoman for the Nuclear Regulatory Commission said it’s too early to determine whether the gap found Thursday posed a problem.
“That is the question we expect the company to provide us an answer with, and we will assess it before making a determination,” NRC spokeswoman Viktoria Mitlyng told The (Toledo) Blade.
The agency plans to send more inspectors to the plant operated by Akron-based FirstEnergy Corp.
FirstEnergy spokeswoman Jennifer Young said the gap runs along the length of a 25-foot cut made in 2011 when a new reactor head was brought into the plant.
The gap is six to 12 inches wide. “It’s probably an air pocket that got in there when the concrete was poured,” Young said.
She said there’s no sign of it on the outside of the mostly concrete-and-steel structure, which is intended to protect the plant from events like storms or terrorist attacks and protect the public in the event of a catastrophe.
FirstEnergy will eventually seal the structure again once its new steam generators are installed.
“They will have to address this void before they start up,” Mitlyng said. We will be evaluating how they handle the concrete pouring and the conditions to make sure these conditions do not recur. We need to understand what happened and why, and what possible implications there might have been”
The shield structure at Davis-Besse came under scrutiny three years ago after several hairline cracks were found in the concrete. FirstEnergy determined they were caused by moisture seeping into the concrete during a blizzard and that the structural integrity wasn’t affected.
The utility said in September that more cracks were found, but said the structure was safe. Antinuclear groups questioned whether the structure was compromised after the first cracks were found.
Regulators and FirstEnergy both think the cracks are unrelated to gap in the concrete found this past week.