SAN DIEGO - Dismantling the San Onofre nuclear power plant in Southern California will take two decades and cost $4.4 billion, but spent radioactive fuel will be held at the site indefinitely, according to a game plan from Southern California Edison.

The price tag could make it the most expensive decommissioning in the 70-year history of the nuclear power industry, U-T San Diego reported.

The plant was shut down in 2012 after a small radiation leak led to the discovery of extensive damage to steam-generator tubes that carried radioactive water. Edison, which operated the plant, closed it for good last year.

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On Friday, the utility laid out a draft plan for dismantling the twin reactors and restoring the property north of San Diego over two decades, beginning in 2016.

As early as 2019, the spent nuclear fuel would be transferred from cooling pools to dry storage in reinforced steel canisters, where it would remain until the federal government comes up with a permanent storage plan.

Highly radioactive reactor parts also will be stored in canisters, while those with lower levels of contamination will be taken to disposal sites in Texas and Utah.

Edison's plan estimates that the decommissioning process will have minimal impact on local air and groundwater quality or on noise and traffic congestion.

The final decommissioning plan will be submitted to the Nuclear Regulatory Commission as soon as September.

Edison CEO Ted Craver told investors and analysts on Thursday that the utility already has enough money on hand from customers to pay for the project.

There's still a question about how much utility customers will be asked to cover for billions of dollars in other costs, such as the price of the defective equipment and the replacement power purchased after the plant was shut down.

Edison, and the plant's minority owner, San Diego Gas & Electric Co., have been negotiating with consumer advocates and state officials over how to divide those costs and have proposed a settlement agreement.

The California Public Utilities Commission must approve the deal.