UNFORTUNATELY, THE QUESTION of why the Kennedy Commission did not formally recommend a nuclear moratorium threatens to dominate public consideration of its report on Three Mile Island and, consequently, to divert attention from the commission's more important recommendations for changes in the way nuclear reactors are regulated and run.

One presenting their reporting to Congress, commission members were asked again and again why they did not recommend one or another type of maratorium. Chariman John G. Kenneny and some of his colleagues repeatedly tried to remind the congressmen that in thinking about a moratorium they should ask: for what purpose? Is it intended to provide a pause during which specific changes can be made, or is its purpose merely to be symbolic -- evidence that nuclear power poses an imminent danger and that the critics were right all along? In considering a moratorium proposal, they said, look closely at its precise provisions and ask whether they will, in fact, achieve the intended goal.

The commission itself concluded that a moratorium is needed only to impose a strict deadline for making essential improvements in the nuclear system. Some belived that, without a formal moratorium, the industry and the NRC could not be jolted out of a business-as-usual attitued. But others believed that the impact of the accident itself, the report and the steps that would be taken by the president and Congress would be enough to induce the needed change in attitude. All agreed that a moratorium per se was secondary.

What the commission on Three Mile Island finally did recommend was that the Nuclear Regulatory Commission not issue any new permits to build or operate a reactor until it has determined in each case that the necessary improvements have been made. These include the introduction of numerous new safety measures, a competency test for utilities, new training programs for reactor operators and approved state and local emergency plans. In fact, what this amounts to is a moratorium -- since it will take many months to do all these things. But it is a morathorium applied on a case-by-case basis, on the merits not across the board. This approach would penalize badly run utilities or poorly sited reactors but it would also encourage the resolution of long-standing safely problems. It is more likely to acheive the fastest possible improvements in nuclear safety than the arbitary three-year moratorium proposed by Sen. Gary Hart and Rep. Morris Udall, the chairmen of the chief congressional committeess on nuclear power. The shorter pause that the NRC is expected to announce today reportely conforms quite closely to the commission's recommendation. That recommendation puts the emphasis where it properly belongs: on the improvements that have to be made to ensure a tolerable ddgree of safety.