Largely ignored in the light of press revelations of possible atom bomb capabilities in Pakistan, India, Israel and South Africa, a small U.S. program has been making quiet, steady progress since 1978 in the struggle against nuclear-weapons proliferation.

The RERTR program (for Reduced Enrichment in Research and Test Reactors) was created during the Carter administration to combat what was then a newly perceived threat -- namely, fuel used at nuclear research reactors in more than 40 nations was a potential source of atom bomb material for governments or subnational groups interested in making nuclear weapons. Since then, the program has been developing substitute reactor fuels that cannot be used to make nuclear weapons. Now, after nearly 10 years of R&D and only three years from successful completion, the program is in danger of being eliminated, victim both of an unexplained loss of support from the Reagan administration and of fiscal myopia in Congress.

In the United States, one research reactor has thus far been converted to using the new fuel, while overseas use of the fuel is about to start. Thus, the global proliferation and terrorism risks associated with research reactors remain essentially unchanged from a decade ago:

More than 140 nuclear research reactors worldwide -- including one each in Iran, Libya, Pakistan and South Africa -- use as fuel highly enriched uranium, the same material that fueled the Hiroshima A-bomb. Certain reactors have enough fuel on site for one or more implosion-type atom bombs. For other reactors, fuel from several reactors would have to be pooled to be sufficient for a bomb.

Bomb-usable uranium can be isolated from fuel-plates or fuel-rods using straightforward chemical techniques widely described in public literature.

According to recent government estimates, the United States will export about half a ton of highly enriched uranium to foreign research reactors in 1987, enough for at least 20 nuclear bombs if diverted.

Some foreign research reactors have at their sites a reserve supply of fresh, unirradiated fuel that could be diverted with negligible radiation hazard. At many low-power reactors the fuel in the core could likely be removed without the handlers receiving radiation doses larger than those allowed workers in the U.S. nuclear industry annually, according to an analysis by Daniel Hirsch at the University of California, Santa Cruz.

In the United States and several other countries, many research reactors are located on university campuses, where security often consists of a single lock and a burglar alarm, both of which could be disabled easily by sophisticated terrorists.

Within three years' time, however, the United States will be in a position to end all further U.S. shipments of bomb-grade uranium fuel to foreign research reactors, if the RERTR program is allowed to finish its mission. According to a recent program report, all research reactors now requiring U.S. exports of fresh bomb-grade fuel (the United States is virtually the sole supplier of this type of fuel in the Western world) will by 1990 be able to utilize new fuels made of low-enriched uranium, which cannot be made into nuclear weapons. Use of the new fuels overseas is due to start next year, and eventually all 86 foreign reactors enrolled in the program could be converted.

In the face of these encouraging developments, the RERTR program is threatened with elimination. In recent years, the program has been funded alternately through the Department of Energy and the Arms Control and Disarmament Agency because of a disagreement between Congress and the Reagan administration over which agency should run the program. This year, however, because of budget pressures, Congress may not provide either agency the required $5.2 million for the program.

The House Appropriations Committee has provided no funding in FY 1988 for the program. The Senate Appropriations Committee has provided no money to DoE for the program, and yesterday a Senate subcommittee eliminated ACDA funding for it. Unless the full $5.2 million is restored when the Appropriations Committee meets today, the RERTR program will effectively have been killed. Kenneth Adelman, outgoing director of ACDA, testified that even a funding level as high as $3.12 million "would be a very serious, if not fatal, blow to the RERTR program . . . and would significantly reduce the likelihood of success of RERTR's objective."

In a policy arena usually beset with frustration and setbacks, the RERTR program stands out as an example of what can be achieved by combining U.S. technological leadership with international cooperation. The program's $5.2 million price tag is a bargain compared with the catastrophic costs we may pay in the future if we leave sprinkled around the globe more than 140 caches of potential atom bomb fuel vulnerable to theft or diversion. Killing the program now, when it is so close to successful conclusion, would be inexcusable. The writer is issues coordinator for the Nuclear Control Institute, a research center on nuclear proliferation problems.