The operator of the stricken Three Mile Island nuclear power plant hopes to send technicians into the still-radioactive containment building this month for the first time.

Metropolitan Edison Co. has asked the Nuclear Regulatory Commission for permission to send two technicians, a request the NRC indicated it probably will grant. The two would wear protective suits and carry oxygen tanks on their backs.

"The part of the building they'd go into is not as dangerously radioactive as the rest of the containment," Richard Vollmer, director of the NRC's TMI technical supply staff, said from Middletown, Pa., where Three Mile Island is located. "However, any technicians we'd allow in there would be fully suited against the environment."

Met Ed wants to photograph the inside of the containment and take paint samples from the walls and structures above water. The damaged reactor is in the lower reaches of the building, under highly radioactive waste water as much as 50 feet deep.

Paint scrapings from the walls will tell engineers what kind of radioactivity and how much of it is above the water line. This will give Met Ed a better idea of how to decontaminate the air inside the building.

Most of the radioactivity in the air is in the form of krypton-85, a gas that emits beta rays and a little gamma radiation and whose half-life, or time it takes to lose half its radioactivity, is 10.5 years. There is as much as 44,000 curies of radioactive krypton in the air of the containment.

Krypton cannot be filtered out of the air and will not dissolve in water, yet any decontamination of the reactor at Three Mile Island must start with a plan to get rid of the krypton.

Met Ed has asked the NRC for permission to vent the air and the krypton into the atmosphere a little at a time, a procedure that could take several months.The NRC has delayed any decision for at least three months while it studies the Met Ed plan and asks for public comment on it.

While the Nrc has not commented publicly on the Met Ed plan it privately disapproves and probably will not allow it. One alternative the NRC is looking at would suck the air into tanks, liquefy it under pressure and cold temperatures, and bury the tanks.