The plant was shut down last year because of premature wear on thousands of steam generator tubes that carry radioactive water from the plant's twin reactors. The steam generators were installed in a $670 million overhaul in 2009 and 2010. SCE announced last month that it will be closing the plant for good.
In legal documents, the utility claims Mitsubishi Heavy Industries Ltd. and Mitsubishi Nuclear Energy Systems are liable for the defective generators, along with costs ranging from buying replacement power to the investment in the now-shuttered plant that the company earlier estimated at over $2 billion.
Majority owner SCE and co-owners San Diego Gas & Electric and the city of Riverside "continue to incur significant financial harm as a result of Mitsubishi's total and fundamental failure to meet its obligations," the filing said.
Mitsubishi said that its contract with SCE limits its liability to around $137 million.
The action represents an early step in what could be a protracted battle over blame for the plant's closure and who should cover the losses.
In a separate case, state utility regulators are considering who should pay for Mitsubishi's replacement generators, ratepayers or shareholders. A decision could be months, or years, away. Any money Edison recovers from Mitsubishi could reduce the exposure of ratepayers.