Federal regulators yesterday agreed with FirstEnergy Corp.'s conclusion that a 1978 blizzard cracked the outer concrete shell of the Davis-Besse nuclear plant in Ohio -- despite concerns that the company's analysis is flawed.

The Nuclear Regulatory Commission yesterday accepted FirstEnergy's assessment that driving wind and rain from the storm and the absence of exterior sealant on the shield building allowed moisture to seep into the structure's concrete walls, where it froze, expanded and caused cracks to develop (E&ENews PM, Feb. 24).

The NRC also approved FirstEnergy's proposal to conduct additional tests on the building and apply a sealant to the structure in Oak Harbor, about 20 miles southeast of Toledo.

But Rep. Dennis Kucinich (D-Ohio) says the Akron-based utility's analysis is incomplete and downplays safety risks. FirstEnergy is pinpointing the storm that struck 34 years ago to detract from other possible causes and secure a 20-year extension for its operating license, which expires in 2017, he said.

"The NRC has accepted FirstEnergy's explanation despite the fact that neither FirstEnergy nor the NRC can explain how wind-driven moisture from the blizzard of 1978 could have possibly caused damage around the entire circumference of the shield building, instead of only where the wind had 'driven' the rain into the building," Kucinich said in a statement.

The cracks were discovered last year by workers at the plant who were replacing a corroding lid or "head" on the reactor. The contractors cut a hole through the plant's 2-foot-thick concrete shield building and found a 30-foot crack in the concrete structure, which is surrounded by a steel containment vessel designed to protect the reactor from natural disasters and terrorist attacks (Greenwire, Feb. 24).

Subsequent investigations revealed other fractures in the 224-foot-tall shield. The reactor was not operating when the cracks were found, and the NRC in December allowed the plant to begin operating again.

Jennifer Young, a spokeswoman with FirstEnergy, said a team of structural concrete and causal analysis experts worked with plant workers to consider an "exhaustive list of potential cracking causes," and the company is standing by its conclusion.

Even so, Kucinich said, the report doesn't explain how wind and rain that struck the portion of the shield building facing the southwest caused cracking throughout the entire structure.

"There was damage around the entire circumference of the building," Kucinich said. "How could damage around the entire circumference possibly be caused by wind-driven moisture when, as FirstEnergy admits, 'the predominant wind direction' was from the southwest? It doesn't make sense."

David Lochbaum, director of the Union of Concerned Scientists' Nuclear Safety Project, said FirstEnergy didn't explain why the cracks weren't discovered when workers cut into the primary containment in 2003 to replace the reactor vessel. If the cracks existed at that time, they should have been identified and reported, he said.

FirstEnergy also failed to study surrounding buildings at the Davis-Besse plant that had the proper sealant. "If you had tested those surfaces to determine whether the cracks were caused by a lack of coating, then you could have gotten more data," Lochbaum said.

Lochbaum said it's crucial to pinpoint the exact reason for the cracking to make sure the building shield is strong enough during emergencies to prevent the release of radioactive material.

"If the problem is something else and it's not the blizzard of '78, then that fix may not protect against the problem that's causing the cracking," he said.