PON INITIALING the Limited Nuclear Test Ban Treaty on August 5, 1963 a few hours short of the 18th anniversary of the atomic bombing of Hiroshima--President Kennedy was reminded of the proverbial first step in a thousand-mile journey. For Kennedy, the treaty was "a step towards peace--a step towards reason--a step away from war." Since that day we have made little progress in this direction--indeed, some might argue that whatever movement has occurred has been retrograde.

Last year, on the same anniversary--the 18th for the treaty--President Reagan approved production of the neutron bomb, one of the weapons that Kennedy had overridden test ban opponents in deciding to forgo. The "doomsday clock" on the cover of the Bulletin of Atomic Scientists, which had been set back to 12 before midnight upon the signing of the test ban treaty, has now been moved up again to only four minutes shy of the final hour.

Glenn Seaborg, the chairman of the U.S. Atomic Energy Commission during the Kennedy administration, has written a detailed and absorbing history of what seems, in retrospect, the innocent and halcyon days of nuclear arms control. Seaborg rightly lays claim to having been an "insider" in the test ban negotiations, and his first-person account benefits from close friendship with other Kennedy insiders--particularly Averell Harriman, the treaty's chief U.S. negotiator and author of a foreword to the book. Like the memoirs of the first AEC chairman, David Lilienthal, Seaborg's book draws heavily upon a daily personal journal that he kept while at that post. Unfortunately, unlike Lilienthal's diary, Seaborg's is often more in the nature of an engagement calendar, containing little of the candid impressions and none of the moral agonizing that characterized The Atomic Energy Years and that makes the latter as much an historical document as the private recollections of one-who-was-there.

This is regrettable, since Seaborg as AEC chairman was surely alive to the dilemmas--ethical and otherwise --inherent in administrating a vast enterprise whose products were the weapons of mass destruction and the ill-starred "atoms for peace." A close associate of his during the Kennedy years spoke recently of Seaborg's "almost childlike enthusiasm" then for the peaceful uses of atomic energy "as a way of trying to find something good to come from the bomb." In Seaborg's book, the peaceful atom properly yields center stage to its more belligerent relative.

As might be expected, the book is most interesting for the light it throws upon the thoughts and actions of Kennedy; a surprise is its insight, reflected through the eyes of Kennedy and Harriman, into the personality of Khrushchev. The spritely premier is portrayed as a skillful rhetorician who was nonetheless deeply concerned with slowing the arms race, a sentiment that put him in constant struggle with the Kremlin's hard-liners. Implicit in Seaborg's portrait of Khrushchev is a view which perhaps had some currency in the Kennedy administration but more recently seems to have fallen out of vogue--that it is possible to deal with the Russians.

The author is plainly sympathetic to Kennedy, both the man and the president, to whom the book is dedicated. It is presumedly not only nostalgia for Camelot but simple oversight that causes Seaborg to treat only as a footnote and an aside two fascinating glimpses into the extent of opposition to the test ban in some circles, and the willingness of Kennedy to "pay any price, bear any burden" to head off a Chinese bomb: During the 1961 test moratorium, Kennedy suspected the AEC of making secret and unauthorized preparations to resume atmospheric testing; in the summer of 1963, Kennedy indicated that he was considering a joint Soviet-American preemptive strike against China's nuclear facilities, and might act unilaterally if the Russians would not go along.

There are no real villains in the piece, but some at least implied criticism of test ban opponents. Surely a perennial among the latter was physicist Edward Teller, whose congressional testimony against the ban Seaborg credits as being the most effective block to its acceptance by Congress. Teller ingeniously discovered a new way in which the Russians might clandestinely test nuclear weapons--in underground salt caverns, behind the sun, etc.--each time treaty proponents seemed on the verge of convincing Senate skeptics that verification of a test ban was possible. Some--including Kennedy and British Prime Minister Harold Macmillan--believed that such delaying tactics not only needlessly prolonged the above-ground testing which fouled the air with radioactive fallout, but actually caused the United States to lose ground in the arms race.

For Seaborg, as well as for Kennedy and Harriman, Senate ratification of the limited test ban treaty in September 1963 was only a partial victory, since all three had hoped for a comprehensive ban on nuclear testing. It is "really appalling," Harriman observes in the book, "to realize what a missed opportunity we had" in the comprehensive test ban--which both he and Seaborg obviously consider a part of Kennedy's uncompleted legacy. The book's last chapter is an unabashed plea for such a ban--"The hour is late. Let us hope not too late" --under the terms of which neither side would be able to conduct tests of new weapons or "proof tests" to see if the old ones still work. A comprehensive test ban, one atomic scientist has observed elsewhere, would be a tacit agreement "simply to let the damn things rot."

The goal of a total ban on testing had gradually receded during the 1961-63 negotiations as a result of opposition in Congress and from the military. Ironically, Khrushchev, who had already agreed to a comprehensive ban in principle, may have retreated from it because of opposition from his own different kind of domestic constituency in the Kremlin and the Strategic Rocket Forces.

Near the end for both men--weeks before his own assassination, months before Khruschev's ouster--Kennedy reflected on an enduring dilemma in the cold war: the irony of how he and the Russian leader had come to "occupy approximately the same political positions inside our governments. He would like to prevent a nuclear war but is under severe pressure from his hard-line crowd, which interprets every move in that direction as appeasement. . . . Meanwhile, the lack of progress in reaching agreements between our two countries gives strength to the hard-line boys in both. . . ." Khrushchev, for his part, lamented on the first anniversary of the test ban the fact that the "certain fund of confidence" it inaugurated had not given dividends in subsequent agreements.

Nearly a generation after the treaty's signing, Seaborg reluctantly acknowledges that the "fund of confidence has been sorely depleted." One might wonder instead, in the wake of events that have depressed Soviet-American relations to a new low, whether that fund is not now, in fact, overdrawn.y