Originally published March 8, 2013 at 1:09 p.m., updated March 8, 2013 at 4:26 p.m.
The report shows Southern California Edison was aware of design flaws with its replacement steam generators years before they were installed at San Onofre nuclear plant. It says Southern California Edison and Mitsubishi's joint team of experts knew the steam generators could produce what's called void fraction that would lead to thinning of the tubes inside the steam generators.
It also indicates Edison considered making changes. But it shows Edison believed the changes carried unacceptable consequences, including a licensing amendment process with federal regulators. Edison installed the new generators in 2010 and 2011 without the fixes.
A thinning tube ruptured last year at San Onofre causing a radiation leak. The plant has been closed ever since.
Damon Moglen of the environmental group Friends of the Earth called the report a bombshell.
"It proves conclusively that Edison was aware of these really troubling problems all the way back in 2005 and rather than doing what they needed to to guarantee safety, they went ahead and disregarded changes," Moglen said.
Edison did not immediately respond to a request for comment. But in the past, Edison has said it would never, and did not, install steam generators that it believed would not perform safely.
The company wants to restart the plant at reduced capacity. After the report was made public, California Senator Barbara Boxer said the Nuclear Regulatory Commission should investigate whether Edison fully complied with its legal obligations at San Onofre.
"A full investigation is critical to any determination on whether it is safe to restart San Onofre Units 2 and 3,” Boxer said.
The NRC would only say its probe is ongoing.