Edison hikes San Onofre payoff demand

Southern California Edison, operator of the now-defunct San Onofre Nuclear Generating Station, is doubling down on warranty claims against Mitsubishi Heavy Industries, the Japanese manufacturer of four steam turbine generators that failed prematurely and ultimately led to the plant's demise.

The two sides have long squabbled over who was responsible for design flaws at the plant.

Back in 2013, called for arbitration through the International Chamber of Commerce, claiming losses in excess of $4 billion were Mitsubishi's fault. For their part, the Japanese manufacturer insists its liability for the faulty designs, which Edison had a hand in crafting, are capped under a warranty agreement at about $137 million.

Earlier this week, Mitsubishi disclosed to shareholders that Edison is now demanding as much as $7.6 billion, a move that sent the company's stock tumbling. Share prices are down more than 8 percent since the announcement, and the stock is trading near six-month lows on the Tokyo exchange.

Arbitration on the matter isn't expected until sometime in 2016, leaving time for more to come to light as authorities consider reopening a settlement case that places the bulk of shutdown-related costs on utility customers who in the past received a portion of their electricity from San Onofre.