SOMETHING OF ENORMOUS potential consequence - and equal delicacy - has been going on in the past several days concerning the South African government's nuclear intentions. It was an international bomb scare of the first order, and President Carter's carefully measured announcement yesterday seemed to reflect both the initial relief and the continuing wariness that his administration feels about the outcome. South Africa, the President said, "has informed us that they do not have and do not intend to develop nuclear explosive devices for any purpose, either peaceful or as a weapon . . . that no nuclear explosive test will be taken in South Africa now or in the future." He added his appreciation of this "commitment" and made a point of noting "we will, of course, continue to monitor the situation there very closely."

What has been going on is this: The U.S. government - in concert with the British, French, West Germans and Russians - has been putting terrific heat on the South African government because there was strong reason to suspect that the South Africans were in fact preparing a nuclear explosion for somethime soon, an explosion of unimaginable political impact, whatever its actual nuclear tonnage. The French foreign minister, Louis de Guiringaud, whose harsh warning to the South Africans made news earlier in the week, led the open, public protest. The other countries, along with France, pushed very hard in private. The upshot has been the South African government's statement cited by Mr. Carter. Either they never were going to develop a nuclear explosive device or they are not going to do so now. Whichever is the case, it is welcome news - though hardly enough to warrant a relaxed return to other business.

There were two very positive, upbeat aspects to the drama that led to the South African assurances. One is that a group of nations who otherwise compete on a wide range of matters, including nuclear ones, were able to get together and act forcefully and fast to indicate to a prospective new nuclear power that the consequences would be if it went ahead. Nothing like that, you will recall, occurred at the time of India's nuclear explosion in 1974. The other promising sign is that so-called peaceful nuclear explosions seem finally and appropriately to be losing their mystique. Mr. Guiringaud had it just right. He declared that "no distinction could be made between an atomic explosion for pacific purposed and one for military nuclear experimentation." That is the case and the "peaceful explosion" dodge has long since deserved the contempt in which it is increasingly widely held.

Why would South Africa want nuclear weapons? Presumably, if it did, for the same scare and symbolism reasons that many other non-nuclear nations with big troubles want them. The grim fact is that over the long haul South Africa could probably acquire nuclear independence: It has great supplies of uranium and could in time develop the technology to do with it as it pleased. For the present, however, the South Africans depend on other countries such as the United States and France to provide it enriched uranium fuel. That means we still have some leverage and some time to act.

Mr. Carter was right in taking the incident as cause to "renew our efforts to encourage South Africa to place all their nuclear power production capabilities under international safeguards and inspections" and to sign the nuclear nonproliferation treaty. But the case is bigger than the South African episode - blood-chilling as that has been. It illustrates, again, the urgency of trying to work out some international discipline in the field of nuclear-weapons and energy development. Partial and ad hoc as it was, the international effort of those who leaned on South Africa shows that it can be done.