By Timothy Gardner
WASHINGTON (Reuters) -Holtec, the company wanting to reopen the Palisades nuclear reactor in Michigan, found corrosion cracking in steam generators "far exceeded" estimates, the U.S. nuclear power regulator said in a document published on Wednesday.
President Joe Biden's administration this week finalized a $1.52 billion conditional loan guarantee to the Palisades plant. It is part of an effort to support nuclear energy, which generates virtually emissions-free power, to curb climate change and to help satisfy rising electricity demand from artificial intelligence, electric vehicles and digital currency.
Palisades, which shut under a different owner in 2022, is seeking to be the first modern U.S. nuclear power plant to reopen after being fully shut.
A summary of an early September call between the U.S. Nuclear Regulatory Commission and Holtec published on Wednesday said indications of stress corrosion cracking in tubes in both of Palisade's steam generators "far exceeded estimates based on previous operating history." It found 1,163 steam generator tubes had indications of the stress cracking. There are more than 16,000 tubes in the units.
Steam generators are sensitive components that require meticulous maintenance and are among the most expensive units at a nuclear power station.
Holtec wants to return the plant to operation late next year. Patrick O'Brien, a company spokesperson, said the results of the inspections "were not entirely unpredicted" as the standard system "layup process", or procedure for maintaining the units, was not followed when the plant went into shutdown.
But he said the return of Palisades is still on schedule and that Holtec wants to fix, and not replace, the steam generators, which he said would last for 30 years after repairs.
"We expect the repair strategy will be to 'unplug' approximately 300 tubes per steam generator that were plugged at original installation, and then address the tubes found during the inspections by plugging approximately 20% of the tubes that cannot be repaired easily and repairing the remaining 80% with sleeving, which is a common and proven repair strategy," O'Brien said.
Holtec still needs permits from the NRC. "Holtec must ensure the generators will meet NRC requirements if the agency authorizes returning Palisades to operational status," an NRC spokesperson said.
The NRC said last month that preliminary results from inspections "identified a large number of steam generator tubes with indications that require further analysis and/or repair."
Steam generator issues can pose problems for nuclear power plants. Parts of the San Onofre Nuclear Generating Station in California were shut in 2012 after steam generators that had a design flaw leaked. Problems with new generators led to the closure of the plant in 2013.