California's march away from the nuclear age has been accelerated by a state Energy Commission decision Wednesday against the proposed Sundesert nuclear power plant.

The commission, whose members are all appointees of Gov. Edmund G. Brown Jr., cited the lack of safe methods for the disposal for nuclear waste from the plant as the main reason for its decision.

The board, by a 4-to-1 vote, also recommended that Sundesert, a $3 billion electricity generating plant proposed for a site 200 miles east of San Diego, not be granted an exemption from the state's tough nuclear safeguard laws.

Sundesert has long been considered by nuclear power advocates here as the proposed atomic plant most likely to get state approval because of its location away from population centers and earthquake fault lines. The plant's advocates in the state legislature, led by member's of Brown's own party, are attempting to overturn the commission's action.

Those supporters won a victory yesterday when the state Senate overturned one of the Energy Commission's rulings and voted 21 to 10 to exempt Sundesert from the state's nuclear safeguard restrictions.

The Senate bill favoring the plant will now go to the state Assembly, where it must go through committee, and is not expected to reach a vote for several weeks. The bill's supporters believe a majority exists for their position, although they admit overriding a probable veto by the governor may pose an insurmountable problem.