For their limitless inventory of real and fanciful horror stories, opponents of a Soviet-American nuclear test ban are now touting a new menace - that in the absence of testing, our nuclear wares may, unbeknownst to us, decay in storage and fail to perform as intended.

In fact, according to newly released congressional testimony by Assistant Energy Secretary Donald Kerr, firing tests in recent years have revealed serious storage-induced defects, verified their correction, and have provided assurance that nuclear weaponry remains in tip-top shape. From this it follows, he said, that the United States can safely endure a brief moratorium - though one that would allow very low-level tests - but any ban beyond three years would incur the risk of invisible rot setting into the stockpile. An implied conclusion to this termites-in-the-armory scenario is that should a desperate moment arrive after a prolonged ban, the U.S. deterrent might not be effective, but even if it is, military planners might be shackled by uncertainties as to whether they are relying on a pile of duds.

Given the political sensitivity attached to the reliability of the ultimate weapon, Kerr's testimony - involving some ace-in-the-hole, previously classified information on life in the stockpile - might be considered the authoritative word on this technically obscure issue. But one of the fortunate byproducts of the age and girth o the nuclear-bomb establishment is that it has spun off a good many alumni who, from the outside, can knowledgeably assess the claims of the pro-bomb zealots. And, in regard to claims for the necessity of testing, it is therefore useful to listen attentively to the combined views of four specialists who, literally, know the bomb from the inside.

Norris Bradbury, who directed the mecca of bomb design, the Los Alamos Scientific Laboratory, from 1945 to 1970, and J. Carson Mark, who headed its theoretical division from 1947 to 1973; Hans Bethe, a Nobel laureate physicist whose calculations established the feasibility of the hydrogen bomb, and Richard Garwin, an IBM physicist and longtime Los Alamos consultant who is one of the most widely respected and frequently consulted of the government's science advisers. And what they say is that Kerr and his camp are talking obscurist nonsense.

Their dissent from the need to test - to which Kerr was presumably replying in testimony released last week - was expressed Aug. 15 in a letter to the president. What it boils down to is that while test firings are indeed useful for improving nuclear designs, they are not indispensable for verifying the continuing reliability of designs that have been tested, produced and stockpiled. Speaking as people who have been there, they point out that "the assurance of continued operability of stock-piled nuclear weapons has in the past been achieved almost exclusively by non-nuclear testing - by meticulous inspection and disassembly of the components of the nuclear weapons, including their firing and fuzing equipment."

Addressing themselves to the argument that firing tests have revealed and helped correct problems encountered in stored weapons, they respond that, so they have, but that this doesn't mean that the same results could not have been achieved through vigorous and skillful use of other means, regardless of the bombmarkers' preference for actually popping them off. What they've saying in short, is that proof testing need not be the exclusive means for assuring the safe storability of the stockpile.

The controversy may have the appearance of just another one of those instances in which doctors, in good faith,disagree. But test-ban politics go far beyond mere technical differences of opinion. For the academically based arms-control community, still nursing a 30-year guilt hangover from its central role in building the bomb, the test ban retains a symbolic significance that far exceeds its military or political value. For the hardliners, a banso strongly symbolizes an unraveling of military will that not even the most preposterous argument against it is ruled out. Thus, in earlier testimony, Kerr even raised the specter of the Soviets evading a ban by secretly "testing on the territory of allies, in remote and unwatched areas of the atmosphere, or evenin outer space."

The onlynoteworthy thing about such nonsense - given the state of Soviet alliances and the ease of detecting nuclear tests in the atmosphere and space - is the desperation it reveals among test-ban opponents.