The California Coastal Commission has cleared the way for changes in the way radioactive fuel is stored at the defunct San Onofre nuclear power plant.
The commission on Tuesday granted a 20-year permit for Southern California Edison to shift spent fuel into steel canisters sheathed in concrete.
Currently, only a third of the fuel at the site between Los Angeles and San Diego is housed in canisters. The rest is in storage pools.
Critics at a hearing in Long Beach argued the commission was creating a nuclear waste dump that could leak or be damaged by flooding.
However, the Nuclear Regulatory Commission has called the plan safe.
The nation has no long-term storage site for radioactive fuel from commercial nuclear plants.