Federal regulators intend to close a lingering case involving the installation of faulty equipment at the now-shuttered San Onofre nuclear power plant in San Diego County.
Environmental group Friends of the Earth wanted the Nuclear Regulatory Commission to review whether operator Southern California Edison sidestepped rules when it replaced steam generators in a $670 million overhaul in 2009 and 2010.
San Onofre was shut down in January 2012 after a small radiation leak led to the discovery of extensive damage to hundreds of virtually new tubes inside the generators. Edison closed the plant for good in 2013 during a fight over whether the reactors were too damaged to operate safely.
A proposed decision released Monday from the NRC's Office of Nuclear Reactor Regulation said the issue is no longer relevant because the plant closed in 2013.
Edison said in a statement it supports the ruling.
The environmental group said the agency is trying to cover up problems that eventually led to the plant closing down.
"The NRC permitted Edison to design, construct, install and operate defective steam generators, and NRC only came to recognize that there was a problem after there had been an accident involving the release of radiation," Damon Moglen, a senior adviser to the group, wrote in a letter to the agency. "Such willful ignorance of serious safety risks is an indictment of both the agency and the utility. Neither the NRC nor Edison is absolved by the closure of the reactors."
The generators, which resembled massive steel fire hydrants, controlled heat in the reactors and operated something like a car radiator. After the plant was shut down, tests found some generator tubes were so badly eroded that they could fail and possibly release radiation, a stunning finding inside the nearly new equipment.
An NRC investigation found a botched computer analysis resulted in design flaws that were largely to blame for the unprecedented wear in the generator tubes.