The Nuclear Regulatory Commission sent out strong signals yesterday that it will permit rodioactive gas to be vented from the Three Mile Island nuclear power plant without waiting for completion of an environmental impact statement.

The commissioners made it clear that they are worried about instruments and machinery that have been inside the damaged reactor building without maintenance since the accident March 28.

"You can't sit around here and calculate environmental impact while we have a disaster waiting to happen in central Pennyslvania," said Commissioner Joseph Hendrie, pounding his fist on the table.

He later said he was only expressing frustration with the fact that an environmental impact statement on the possible venting of radioactive gas and purging of contaminated water would not be finished before the end of the year.

"There is no clear and present danger," he said, "but we should have been inside the containment to check the condition of the primary system, to replace essential instruments, and we should have done it two months ago."

Pennsylvania authorities and area residents demanded an environmental impact statement, and the NRC promised one, although the laws would allow the NRC to vent the gas anyway if it perceived a health and safety need to do so.

Although Metropolitan Edison Co., which owns the reactor, has argued that the gas can be vented safety over a two-month period, with virtually no radiation dose to the public, several citizen organizations have vehemently opposed the idea.

While disavowing any possibility of disaster, the NRC's reactor regulation Chief, Harold Denton, confirmed after the meeting with the commissioners that "the longer we wait, the more people get edgy."

He said he would report next week on his unsuccessful effects to locate a technology that could deal quickly with the radioactive Krypton 85 gas inside the reactor building in some way other than by venting it to the atmosphere.

"I committed myself to Pennsylvania authorities, that I would not recommend venting until we had exhausted all other possibilities," Denton said. "But with all the suggestions and outlines I've received, none can go from the laboratory to a fullscale operation in less than a couple of years."

He said he thought it would be "imprudent" to wait that long, but declined to say what he would recommend. The five-member commission would have to vote approval of any venting.

Krypton gas was one product of the accident in which the reactor lost cooling water and overheated. Denton said there are approximately 44,000 curies of the material, which technical experts said would give an unprotected person standing inside the containment building a radiation dose of 300 millirem per hour. Background radiation provides a dose of 100 millirem per year.

However, Hendrie argued, controlled release over a period of weeks, "even with the weather just average, without good dispersal wind," would produce a maximum dose to persons outside the plant of perhaps 1 or 2 millirem.

Venting would allow technicians to enter the containment building safely and check equipment, such as ventilation fans, which have been operating unattended since the accident and are vital to continued safety of the plant, Hendrie said.

"We're down to one operable neutron monitor," he said, referring to a radiation counting device, "and various other instruments connected with levels, flows and pressures have gone out of service."