The Latest: Tagged 'steam generator'

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The San Onofre Nuclear Power Plant is seen on April 6, 2012.

A rule allowing nuclear plant operators to replace certain equipment without prior approval from the Nuclear Regulatory Commission is being reconsidered.

Speaking in North Carolina on Wednesday, NRC Chairman Gregory Jaczko said the tubing trouble at San Onofre suggests the rules under which the generators were installed may need to be modified, the Associated Press reported.

The twin reactors, offline for months, will need federal approval to restart. Plant operator Southern California Edison hoped to reopen in time for summer's peak energy use, however no projected timeline has been released.

Earlier this week, NRC Chairman Jaczko announced he will be stepping down from his post.

After nearly eight years on the Commission, I am announcing my resignation as Chairman of the U.S. Nuclear Regulatory Commission, effective upon the confirmation of my successor. My responsibility and commitment to safety will continue to be my paramount priority after I leave the Commission and until my successor is confirmed.

David McNew/Getty Images

San Onofre Nuclear Generating Station

Tubes inside a new steam generator at San Onofre Nuclear Generating Station are showing unusual and potentially dangerous signs of deterioration, federal regulators announced on Thursday.

"The amount of wear that we are seeing on these tubes is unusual for a new steam generator," said Nuclear Regulatory Commission spokesman Victor Dricks.

More than 800 tubes of the San Diego County plant showed a 10 percent thinning in the tube wall, officials said. 69 others had at least 20 percent thinning. And two tubes needed to be plugged and taken out of service because a third of the wall was worn away.

"If you have that kind of thinning anywhere along the length of the tube, you have a problem because it degrades the integrity of the tube, which can contribute to leaks," explained Dricks.

Safety implications could be "very severe," warned Joram Hopenfeld, a retired NRC engineer and researcher, as the tubes are one of the primary barriers to radioactivity