In this Sunday, June 17, 2012 photo, Elmo Collins, regional administrator of the Nuclear Regulatory Commission, speaks during an interview in San Juan Capistrano, Calif. The NRC is holding a public meeting to discuss the state of the San Onofre nuclear power plant on Monday in San Juan Capistrano. After months of investigation, federal regulators have determined that design flaws appear to be the cause of excessive wear in tubing that carries radioactive water through the power plant. (AP Photo/Grant Hindsley)
SAN JUAN CAPISTRANO, Calif. (AP) — Federal regulators said Monday that a botched computer analysis resulted in design flaws that are largely to blame for unprecedented wear in steam tubes at the San Onofre nuclear power plant, but it isn’t clear how the problems can be fixed.
The preliminary findings by a team of Nuclear Regulatory Commission investigators were disclosed nearly five months after the seaside plant was shut down following a break in a tube that carries radioactive water. There is no date to restart either of its two reactors.
The problems center on excessive tube wear in steam generators that were installed at San Onofre during a $670 million overhaul in 2009 and 2010. Tests found some tubes were so badly corroded that they could fail and possibly release radiation, a stunning finding inside the virtually new equipment.
Long unknown was what was causing tubes to vibrate and rub against each other inside the massive machines, manufactured by Mitsubishi Heavy Industries.
Greg Werner, who headed the federal team, said a Mitsubishi computer analysis vastly misjudged how water and steam would flow in the reactors. Also, changes intended to improve manufacturing were never thoroughly reviewed in the context of the generator design, resulting in weaker support around bundles of tubes that contributed to vibration, he said.
The plant’s operator, Southern California Edison, could face penalties, while problems at the plant have raised fears of a nuclear accident in Southern California and cut off one of the region’s important sources of power.
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