The odds of a meltdown at the Davis-Besse nuclear power plant were higher than people were led to believe prior to the plant's shutdown last year, the Nuclear Regulatory Commission said yesterday.
The NRC said the risk posed by the faulty design of the plant's original high-pressure injection pumps is no doubt higher than the agency's baseline “green” rating for safety significance.
The agency said it needs more information from FirstEnergy Nuclear Energy Co. before it can make a final determination as to the degree of risk.
Davis-Besse has been idle for 20 months, after management and performance issues that emerged since the discovery of a near-hole in the plant's reactor head in March, 2002.
The rust problem is the worst of its kind in U.S. nuclear history.
The NRC rates certain problems on a color-coded scale for safety significance, starting with green for very low significance. White, yellow, and red colors are used for moderate to extreme risks, with red being the most dangerous.
The agency gave FirstEnergy a red finding on Feb. 25 for letting Davis-Besse's reactor head become so thinned by rust that it nearly burst and allowed radioactive steam into the containment building. A replacement head has been installed.
On Wednesday, the NRC formalized its safety assessment of Davis-Besse's containment sump flaw as yellow.
Officials have said the only reason the utility did not get a red finding was because it's possible the sump would have worked in accidents that involved only a small loss of coolant.
The sump, which has been rebuilt, was prone to clogging if coolant losses were medium or heavy.
The sump is designed to work in conjunction with Davis-Besse's pair of high-pressure injection pumps if a major accident occurred. Those pumps would be used to inject coolant water forcibly over the reactor if the plant lost off-site power.
At some point, the high-pressure injection pumps likely would be spraying recirculated sump water, which likely would have bits of debris collected off the floor. Company officials have found that debris could make the pumps overheat, vibrate, or otherwise fail. That would render them useless at a critical time, officials have said.
FirstEnergy is in the process of testing its plan for rebuilding Davis-Besse's high-pressure pumps at an Alabama laboratory. A lab spokesman told The Blade yesterday preliminary test results are encouraging.
In addition, Richard Wilkins, a FirstEnergy spokesman, said the company is pleased by results so far. Rebuilt pumps have operated in the lab for more than a month without clogging, Mr. Wilkins said.
Jack Grobe, chairman of the NRC panel overseeing Davis-Besse restart efforts, said in a letter sent Wednesday to Lew Myers, FENOC chief operating officer, that “escalated enforcement action” is being considered as a result of the agency's latest finding.
The NRC believes FirstEnergy has violated a federal regulation by failing to make sure the pump would have worked years ago, the letter said.
For more information on Davis-Besse, go to www.toledoblade.com/davisbesse.