The Nuclear Regulatory Commission has proposed the largest fine in its history, a $5.45-million penalty, against FirstEnergy Nuclear Operating Co. for alleged violations of NRC rules at the company's Davis-Besse powerplant in Ohio.

The largest share of the fine, $5 million, is for restarting and operating the plant in May 2000 "without fully characterizing and eliminating leakage from the reactor vessel head," the NRC contends. That problem "led to significant corrosion damage," the commission said in announcing the penalty on April 21.

The company, a unit of FirstEnergy Corp., Akron, said in a statement that it is reviewing the NRC notice and proposed fine. The company said that after the corrosion problem was discovered and reported to regulators in 2002, it "investigated the causes of the problem, replaced the reactor head, and made numerous staff changes, as well as enhancements to plant programs and equipment." Since the plant was restarted in 2004 it "has operated safely and reliably," the company said.

FirstEnergy has 90 days to respond to the proposed penalty. NRC says it earlier had "referred Davis-Besse issues" to the U.S. Justice Dept.

Luis Reyes, NRC executive director for operations, said, "This substantial fine emphasizes the very high safety and regulatory significance of FirstEnergy's failure to reply with NRC requirements and the company's willful failure to provide the NRC with complete and accurate information."

The commission also issued an order to a system engineer, barring him from NRC-regulated activity for five years. The engineer, Andrew Siemaszko, no longer works at Davis-Besse, NRC said. Wilkins says the engineer left the company in 2002.

Siemaszko's attorney, Billie Garde, strongly criticized NRC's announcement. In a statement, she said that Siemaszko is innocent and was a courageous individual who tried to clean the reactor head during the 2000 outage. Garde claimed, "The allegations made by the NRC reveal the agency's serious misunderstanding of the facts, at best, or deliberate misrepresentation, at worst."

Davis-Besse, in Oak Harbor, Ohio, opened in 1977. It has a single, pressurized water reactor, with a capacity of 835 Mw, says Richard Wilkins, a spokesman for FirstEnergy Corp.

In May 2000, NRC said, the plant was started after being down for refueling and maintenance, but a required cleaning and inspection of the reactor vessel head was not done, the commission said. There then was leakage through tubes that penetrated the reactor head, which led to significant damage to the head.

In 2001, the commission called for an inspection of such tubes at Davis-Besse and other nuclear plants. First Energy asked to be allowed to operate Davis-Besse for three more months before shutting down for that inspection. Based on information the company supplied, NRC said, it let Davis-Besse keep operating until Feb. 16, 2002.

But Reyes said, "FirstEnergy supported its request with inaccurate and incomplete information about the cleaning and inspection of the reactor vessel head in 2000. Had the NRC known that the plant was being operated with leakage through the reactor vessel head, the agency would have taken immediate action to shut down the plant."

The corrosion damage was found about three weeks after the shutdown. The plant stayed closed until March 2004 while the reactor vessel head was replaced and other changes made.

Since the restart, Reyes said that "it has operated safely and continues to operate safely."