Federal officials yesterday raised the possibility that the Three Mile Island nuclear plant is so badly contaminated with radioactivity that it may never reopen to generate electricity.

The Nuclear Regulatory Commission has raised this question in blackground briefings it has given senators and representatives from Pennsylvania. The NRC has also raised the question with members of Congress with oversight roles in nuclear energy generation.

"It might be a $1 billion mausoleum," said Sen. Gary Hart (D-Colo.), chairman of the Senate Public Works subcommittee on nuclear regulation. "It might be more expensive to clean up the plant than it was to build."

Radioactivity inside the four-foot-thick concrete containment has been measured as high as 30,000 rems per hour - almost a hundred times the lethal dose - according to officials. At the very least, this means that reactor fission products like iodine-131 and xenon-133 are all over the floor, ceiling and walls of the concrete containment.

There is a possibility that more poisonous fission products like cesium-137 and strontium-90 are in the containment. These fission products have half-lives of 29,000 years, meaning they lose only half their radioactivity in that time period.

"The contamination inside the containment building is unprecedented in the history of nuclear power," Rep. Morris K. Udal (D-Ariz.), chairman of the House subcommittee on energy and the environment, said. "It's so bad it will be months before any possible cleanup can begin, if indeed a cleanup is possible."

There are conflicting reports on how much of Three Mile Island's nuclear fuel has been damaged, how badly it's been damaged and how much radioactivity the damage has released from the reactor into the containment and into the waste water used to cool it.

One report had it that up to 50 percent of the 36,000 fuel rods had been damaged. Another report said only 30 percent were damaged. A third report said 10 percent of the rods were damaged. Most reports agree that the damage fuel did not overheat badly enough to melt, but that many of the fuel rods were "close" to melting temperatures.

"Nobody's seen those fuel rods, that's the trouble," Udall said. "You can't open up the top of the reactor and look in, it's just too badly contaminated in there."

Reports from Pennsylvania where Three Mile Island is located said that "several" employes of the Metropolitan Edison Co., which runs the reactor, has volunteered to go inside the room where the reactor is housed. Their offers were all refused because "it would be suicide."

The NRC has told members of Congress that it will be months before an inspection can be made of the containment building where the reactor room is housed. Even then, a robot will have to be used in the inspection because the building will be too hot for human entry.

The bulk of the radiation being measured inside the containment is believed to be radioactive xenon-133, a gas with a half life of five days. Iodine-131 also escaped in large quantities inside the containment and has probably condensed as a liquid on the walls of the containment. Iodine-131 has a half life of eight days.

Waste water in sump tanks in an auxiliary building outside the reactor and its containment is also so highly radioactive it cannot be inspected. A cleanup of these tanks cannot begin for weeks or even months, but will probably be attempted because they're somewhat exposed to the open air while the reactor and containment are not.

The shut-down plant lies alongside a second nuclear unit at Three Mile Island that had been closed for refueling. The loss of electricity at the stricken plant has meant that the company has had to buy electricity from other utilities in Ohio and Pennsylvania at an additional cost of $600,000 a day.