The Nuclear Regulatory Commission ruled yesterday that the mental health of people living near Three Mile Island should be considered before allowing even the undamaged reactor on the island to start up again and generate electricity.

While it did not call mental health an overriding issue, the NRC said it was of such "real and substantial concern" that it ought to be brought up during hearings to allow the undamaged reactor to restart.

"What the commission is saying is that psychological, sociological and economic distress should all be considered in hearing the licensee's application to resta rt the plant" NRC General Counsel Leonard Bickwit Jr. said yesterday. "In fact, the commission may consider funding any intervenors who present arguments about such distress when the time comes to argue it."

That time will not come before Feb. 1, which is the date the five-member NRC set as the starting date for formal hearings on the Three Mile Island restart. That means it will be at least a year before a license can be given for the undamaged reactor to restart, assuming such a license is granted.

The NRC ruled that the time between now and Feb. 1 be devoted to a pre-hearing process that includes the taking of petitions, response to petitions, the amending of petitions and the filing of testimony. The NRC allotted 180 days to these procedures.

The NRC estimated the hearings themselves would take 60 days, then gave its Atomic Safety and Licensing Board another 50 days to file its findings and at least 45 days to make a decision on the restart application.

Conceivably, the board could waive any decision to the full NRC commission, if only because of the mental health issue. If that happens, the five-member commission will decide whether to license the undamaged reactor at Three Mile Island.

The ruling that residents' mental health should be considered could be a landmark in the regulatory legal process. The NRC's Bickwit points out that the only real precedent in this proceeding came in 1972, when the 2nd U.S. Circuit Court of Appeals considered a challenge by residents of lower Manhattan to the planned construction of a combination courthouse and jail.

"In that case, the court considered the fears of families worried about riots and disturbances in the prison," Bickwit said. "In this case, we will consider the fears of people with regards to radiation."

In other Three Mile Island developments:

An Amish church leader told a Pennsylvania committee in Harrisburg that many members of the strict sect didn't hear about the accident at Three Mile Island until a week after it happened.

"I'd say a week had gone by before they knew of the disturbance at TMI," said Andrew Kinsinger, chairman of the Old Order of Amish Steering Committee. Kinsinger pointed out that few Amish read daily newspapers and even fewer have radios, television sets and even telephones.

The first truck carrying radioactive tools and contaminated clothing worn by workers at TMI left there and was as far as Illinois last night on its way to the nuclear burial ground at Hanford, Wash.

The truckload of 55-gallon steel drums crossed into Ohio under escort of an Ohio Highway Patrol cruiser, a sharp departure from last May when a shipment of radioactive waste water from TMI passing through Ohio caused a furor among state officials who had not been notified.

The nuclear waste truck was accompanied by a van, whose passengers were rotating the driving of the truck to keep it moving. Ohio Turnpike officials said they'd been told t e truck would stop only for food and fuel.

At Three Mile Island itself, technicians were drilling into the contaminated containment building to sample radioactive waste water about the same time a worker was contaminated with some of the water. He was apparently contaminated with about 25 millirems when his outer protective clothing came in contact with his left arm.