California turned away from a nuclear future yesterday when a legislative committee followed Gov. Edmund G. (Jerry) Brown Jr.'s lead and rejected legislation that would have permitted construction of the $3 billion Sundesert nuclear power plant.

The action, for all practical purposes, means that no new nuclear plants will be approved in California at least as long as Brown is governor. It also draws more clearly a prospective line of political conflict between President Carter and Brown, who is viewed both here and in Washington as a challenger for the Democratic presidential nomination in 1980.

"The legislature would send me that [Sundesert] bill in a minute if I gave the slightest signal I would sign it," Brown said recently. "I'm never going to give that signal.

The rejection of Sundesert could mark a national turning away from nuclear power to alternative sources of energy. Only Wednesday the House Government Operations Committee called for a fundamental re-examination of nuclear energy along lines similar to those laid down by the Brown administration in California.

Even some opponents of nuclear plants agree that Sundesert has better credentials than many other atomic proposals. The plant, which would have been built far from urban concentrations near the town of Blythe in the desert 160 miles east of San Diego, was the only pending nuclear power plant in the United States that had received both federal and state clearance for site safety, including earthquake safety.

Despite this advantage and repeated testimony that the San Diego area faces an energy shortage in the mid 1980s, backers of the project failed to convince the legislature, as required by law, that they had a completely feasible scheme for disposing of the reactor's nuclear waste safely.

In 1976 California voters rejected, 2-to-1, an initiative that would have banned nuclear power plants in California. They did so partly on the basis of arguments that the legislature had already passed bills that would ensure safeguards on future nuclear plant siting.

One of those safeguards was the nuclear wastes law. The San Diego Gas and Electric Co., which would have built the Sundesert plant, presented various witnesses who argued that an adequate waste disposal technology is available, but they failed to convince the State Assembly resources Committee.

Brown was chiefly responsible for the rejection of Sundesert. First, the State Energy Commission appointed by the governor turned down the nuclear plant on a 4-to-1 vote. Then, after a bill to exempt the Sundesert plant from the waste disposal requirement was passed by the state Senate, Brown's allies in the Assembly leadership sent the measure to a committee where the odds were stacked heavily against it.

The bill was defeated on a 4-to-7 vote, with three Republicans and one Democrat favoring the measure and seven Democrats voting in opposition. The partyline character of the vote, assured that the issue will be a major one in this year's election camapign, where Republicans are expected to argue that Brown's antinuclear stand is hurting the energy and employment future of the state.

In rejecting the nuclear plant over the opposition of business and labor organizations, the Brown administration and the legislature committed themselves to alternatives which include construction of a coal-fired plant and the repowering of an existing plant.

But there appears significant air quality hurdles to building any coal-fired plant in California, where such plants presently do not exist.

Both sides waged scare campaigns in the days before the voting, with supporters of Sundesert arguing that rejection of the plant would mean turning out the lights in California while opponents talked of nuclear horrors arising from the dangers of undisposed atomic wastes.

Few of the spokesmen on either side appeared ready to concede that both the nuclear plant and the coal plant pose high risk, a point made yesterday before the voting by Marilyn G. Ryan, one of the Republican Assembly members who voted against the bill.

"There are very high risks involved in every energy source," she said. "No one is willing to put risks in his back yard."