The Nuclear Regulatory Commission removed a major obstacle yesterday to licensing the Seabrook, N.H., nuclear power plant for low-power testing.

The NRC voted 4 to 1 that a new utility-drafted evacuation plan for the six Massachusetts municipalities within Seabrook's 10-mile emergency zone could be considered in lieu of a state proposal.

"We find that the plan is bona fide and in the realm of the possible," the NRC said in a nine-page order. "That decision does not require us to evaluate every detail of the proposal." Much stricter standards must be met for a full-power operating license to be approved.

New Hampshire Yankee, operator of the plant, submitted an evacuation plan after Massachusetts Gov. Michael S. Dukakis (D) refused to file a state proposal.

Dukakis said geographic and demographic characteristics of the seacoast area make it impossible to evacuate safely under any conditions, a stance that has further stalled the oft-delayed $5.1 billion plant. Dukakis called the commission's decision "extraordinary."

NRC Chairman Lando W. Zech Jr. said the vote means that Seabrook could receive a low-power license within "weeks or perhaps months" if two technical issues are resolved. They involve in-service inspection of steam generator tubes and accumulation of mussels and other marine life in cooling systems.

The NRC also voted, 5 to 0, to approve a full-power license for the third reactor at the huge Palo Verde nuclear power plant 36 miles west of Phoenix, despite earlier concern about possible defects in its German-built coolant pumps.

The facility will become the nation's largest commercially operated nuclear power plant, with each of the reactors producing nearly 1,300 megawatts of electric power. Only sites in the Soviet Union, France and Japan, using four or more reactors, produce more total energy.