The chairman of the Nuclear Regulatory Commission said yesterday that the NRC might take control of a stricken nuclear power plant in the event of another accident like Three Mile Island.

"It gets difficult if we're asked to switch switches and turn valve wheels," NRC Chairman Joseph M. Hendrie told the Senate subcommittee on nuclear regulation, "but there could be circumstances where we'd assume command of licensee employes, where we'd deputize the plant's operators like the National Guard and where we would go into the plant and take over its management."

Hendrie said the NRC will never again stand back the way it did during the first three days of Three Mile Island. It was not until the accident's fourth day that the NRC's Harold Denton, the director of nuclear regulation, went to Three Mile Island to act as the Federal government's spokesman to explain the accident to the public and to Pennsylvania Gov. Richard Thornburgh.

"I think it's clear that after Three Mile Island, the commission can't stand back from another accident," Hendrie told the subcommittee. "It's clear that the people want to hear directly from the appointed chiefs of this agency and it's just as clear that we'd be drawn in to take a hand in another accident, if it happened."

To a man, the five commissioners told the subcommittee they would not tolerate another Three Mile Island, where plant operators withheld crucial information about the accident for several days. They mentioned as examples of withheld data the 2,500-degree temperatures inside the nuclear core and the hydrogen explosion inside the containment indicating damage to the core.

"These numbers should have been reported to the NRC," Commissioner Peter Bradford said. "Not so much because a law requires it but because it's important to public health and safety."

"We have to be confident that utilities are going to send important safety information to us promptly," Commissioner Victor Gilinsky said. "If there's any question about getting this information, then I think we have to ask the question of whether these machines should be in private hands."

Gilinsky said the NRC has already taken some steps to make sure that certain information is supplied promptly to the NRC by installing direct telephone links in the control rooms of all operating nuclear plants in the United States. He said the NRC is also making it a requirement that power plants install instruments that show the level of water over a nuclear core and make direct measurements of temperature inside the uranium fuel bundles.

"We should have had temperature measurements displayed right inside the control room at Three Mile Island," Gilinsky said. "What we had was a computer printing question marks when the temperature ran over 750 degrees."

Bradford said that if he knew on the first day of the accident that the core at Three Mile Island was no longer covered by cooling water, he would have suggested the region around the plant be evacuated. Gilinsky hinted he would have done the same thing.

"The question was raised about what we might have done that day [March 28, first day of the accident] if we knew about the temperatures and the hydrogen explosion," Gilinsky said. "There is no question in my mind that the thoughts of the staff and commission would have turned immediately to evacuation."