The Nuclear Regulatory Commission agreed yesterday to lift a freeze on the processing of nuclear power plant licenses, but took care to leave the gate open for possible changes in licensing procedures.

The NRC staff had tried to life the freeze last month but retreated when the President's Commission on the Accident at Three Mile Island protested. Its members said they feared their forthcoming recommendations might be ignored.

Under yesterday's decision, the NRC staff will proceed with applications for construction permits and new operating licenses, but none will be issued by the NRC until after the presidential commission makes its final report. That report is expected Oct. 25.

"We'll look at the report and see what their recommendations are," considering them as part of the requirements for new licenses, NRC Chairman Joseph M. Hendrie said. He told reporters later that this would enable the licensing procedure to continue without ruffling the presidential commission's feathers any further.

"I don't see any advantage in confrontation," Hendrie said.

Letters to be sent shortly to all operating plants, license applicants and plants under construction will set forth the NRC's list "of things and pretty clearly are going to be required, so we suggest you begin implementation," Hendrie said. The letters will state that "several other investigations, including the presidential commission and the NRC's special inquiry group, may lead to additional requirements."

Commissioner John F. Ahearne asked the staff for an assessment of a possible shutdown of all power plants under construction by Babcock & Wilcox Co., which built Three Mile Island near Harrisburg, Pa. "There are concerns that B&W plants are more sensitive, less forgiving" of error than other units, Ahearne explained after the meeting. "This isn't anything more than a question."

B&W reactors are under construction in Tennessee, Michigan, Washington and Virginia. The unique aspects of the B&W design, which involve the rate at which water flows through the reactor core, were examined closely after the March 28 accident in Pennsylvania. The eight operating B&W plants were ordered to make some changes but the NRC said the design was not inherently unsafe.

Since then, an NRC task force has drawn up a list of 24 technical and procedural changes made necessary in all present and future reactors by what was learned from Three Mile Island. These changes will have to be implemented by Jan. 1, 1981, at the latest, but Harold Denton, chief of reactor regulation, said yesterday he wants 12 of them in effect before any new plant gets the go-ahead to run.

These include new instruments to show when the reactor core is uncovered and to indicate the position of certain valves, a vent at the top of the reactor to let off any hydrogen bubble, revised procedures for taking water samples and the stationing of a technical adviser on each shift.

Hendrie said he had reached agreement in a telephone discussion with presidential commission Chairman John G. Kemeny that the changes ought to be required of operating plants, but had not discussed further the questions on new units. A spokesperson for Kemeny said the commission will have no comment on the NRC action until its meeting next week.