The 12 members of the presidential commission that investigated the Three Mile Island accident told Congress Yesterday that they feel their recommendations on nuclear power come close to calling for a temporary halt to nuclear construction.

"I don't think the impact of our recommendations is fully appreciated," John G. Kennedy, chairman of the White House commission and president of Dartmouth College, told a joint hearing of the Senate and House subcommittees whose jurisdiction is nuclear energy oversight.

"We have recommended that no new licenses be issued unless certain things happen, unless licensees [utilities] raise safety standards, get the approval of state and local emergency [evacuation] plans and conform to new siting requirements.

"We are, in fact, calling for what I would call a moratorium," said Theodore B. Taylor, a commission member and a Princeton University."Look carefully at our reccommendation, which says no new licenses of any king until certain things are done, until an energency plan is approved by the states. These emergency analyses have never been done before."

The commissioners defended their action in not recommending a formal halt to nuclear power construction in the United States, saying that they found it impossible to call for a moratorium whose conditions they could not know, predict or help form.

"It's easy to say, let's start the moratorium," Kemeny told the two subcommittees, chaired by Sen. Gary Hart (D-Colo.) and Rep. Morris K. Udall (D-Ariz.). "But how do you do that? Do you tie it to a siting policy? How long do you make it? We never could get one vote more than six on any single moratorium recommendation."

The commission voted on at least three versions of a construction moratorium; one that would have halted construction for two years, another that would have halted construction while a new siting policy was hammered out and a third that would have stopped nuclear power construction indefinietly. All failed to win a majority.

"I did not vote on the moratorium tied to siting," Kemeny said. "Why?Because the Nuclear Regulatory Commission could have said: "Okay, we have a new siting policy and therefore the moratorium is off.' It was not the right way to do it, in my opinion."

The commission was just as staunch in its defense of a recommendation that the NRC be abolished, even in the face of critcism of the move by key senators and members of Congress on the two oversight sub-committees.

The commission proposed a new agency rub by a single administrator instead of five commissioners, to be inside the executive branch instead of outside as an independent regulatory agency. The commission urged making the NRC more like the Food and mental Protection Agency.

"Such agencies are quite vulnerable to political direction from the White House and other executive agencies," said Sen. Jennings Randolph (D-W. Va). "Is it appropriate to have nuclear regulation subject to such pressure?"

The commissioners replied that they recommended a "restructuring" of the NRC, together with establishment of a nuclear oversight committee appointed by the president and reporting to the president and Congress on the safety performance of the industry and the newly created agency in the executive branch.

"We would not buy one without the other," Kemeny said. "The two would have to be a package deal to work effecftively."

"We want this oversight committee to report to the American people what has been the response of its nuclear regulatory agency," Taylor said. "We need a time of probation for the nuclear industry and we need to have a basis for the public to determine if the delinquent should be kicked out of school or allowed to continue."