LOS ANGELES, Feb 6 (Reuters) - The owner of a shuttered Southern California nuclear power plant was aware of problems with its new steam generators before they were installed, two lawmakers said on Tuesday, citing a report by the maker of the equipment.
In a letter to U.S. Nuclear Regulatory Commission Chairman Allison Macfarlane, Senator Barbara Boxer and Representative Edward Markey said a 2012 document by Mitsubishi Heavy Industries Ltd, maker of the San Onofre power plant's steam generators, found that some safety modifications were rejected by both Mitsubishi Heavy Industries and plant owner Southern California Edison due to "unacceptable consequences."
The potential changes may have raised the possibility that the plant would need to seek a license amendment because of changes to the steam generators' design, the lawmakers said the report showed.
In the letter, they said the report also shows that Edison and Mitsubishi's decision to reject those modifications contributed to the faulty steam generators and the shutdown of two nuclear reactors at the San Onofre nuclear power plant.
"This newly-obtained information concerns us greatly," Boxer and Markey wrote in the letter.
The report is confidential and Reuters was not able to review it.
Officials from Mitsubishi Heavy Industries and Southern California Edison were not immediately available for comment.
"We have received the letter from Sen. Boxer and Congressman Markey and will respond in the normal course of business," NRC spokesman Victor Dricks said in an email. "As an independent safety agency, we will review all available information in making a judgment as to whether the plant would meet our safety standards if restart were permitted."
Both reactors at the 2,150-megawatt San Onofre plant have been shut down for more than a year due to tube wear problems in the units' new steam generators. Mitsubishi Heavy built the generators and installed them in 2010 and 2011.
The NRC is reviewing Southern California Edison's plan to restart one of those units. Southern California Edison is a unit of Edison International.
San Onofre sits on the California coast halfway between Los Angeles and San Diego. It is the largest power plant in Southern California.