U.S., RUSSIA AT ODDS OVER GEORGIAN URANIUM.

Byline: Michael R. Gordon The New York Times

The United States has been making a quiet effort to have a cache of nuclear material moved out of this volatile region of the former Soviet Union, according to U.S. and Georgian officials.

But the operation to get the material out of Georgia, which is part of a broader program to stem the theft of nuclear-bomb ingredients from Russia and its neighbors, has thus far been thwarted by months of diplomatic impasse between Russia and the United States.

The effort, which was intended to be a model of three-way cooperation, has been the subject of intense negotiations for much of the last year. The United States had wanted to keep the operation secret, but Georgian officials now openly discuss their predicament.

``Indeed, we have several kilograms of uranium,'' President Eduard Shevardnadze of Georgia acknowledged in a recent interview. ``We need to get rid of it.

``But we can't do it independently,'' he said, alluding to financial and technical constraints.

Stored in an obsolete nuclear reactor outside Tbilisi, the Georgian capital, the highly enriched uranium and spent reactor fuel would give an aspiring nuclear power a significant amount of the material needed to make a nuclear bomb.

The cache has been of growing concern to U.S. officials, who fear it is vulnerable to theft by Iranian agents, terrorists from the neighboring secessionist Russian republic of Chechnya or arms traffickers.

Georgian officials disclosed that the material was virtually unguarded when war engulfed this newly independent Caucasian nation early in the 1990s.

Roving bands of militiamen approached the reactor during that time, but officials said the marauders were more interested in stealing cars than uranium.

``During the years of civil war in Georgia,'' said Peter Mamradze, ``the physicists at the institute had many sleepless nights. They were afraid some paramilitary group would come and take it away.'' Mamradze, a physicist by training, is Shevardnadze's chief of staff.

It was such a scenario that prompted U.S. officials to seek tighter control over the hundreds of nuclear laboratories, power plants and institutes spread throughout the former Soviet Union.

During the Cold War the Soviet Union produced about 1,300 tons of highly enriched uranium, Western analysts estimate, and much of it remains scattered widely over the former Soviet republics in poorly guarded sites.

In recent years, several middlemen peddling nuclear material stolen from the former Soviet Union have been arrested in Europe. But there has been no confirmed case of countries or terrorist groups obtaining the ingredients for a bomb through theft.

The United States and Russia have publicly embraced the goal of controlling what some experts term ``loose nukes.'' At a meeting on the subject in April in Moscow, Western leaders and President Boris Yeltsin pledged to work together to stem trafficking in nuclear materials.

But the Georgian reactor is a case study in how good intentions can be snarled by bureaucratic politics, foreign-policy concerns and environmental regulations.

Housed in a weathered building a 20-minute drive from Tbilisi, Georgia's, reactor is an eerie and decrepit monument to the lost days of Soviet science, when vast state resources were channeled into nuclear research.

At its debut in 1959, the research reactor was the pride of Georgia's Institute of Physics. Similar ones were built in other parts of the Soviet Union and in Bulgaria and Iraq.

Shucury Abramidze, the head of the institute's Center for Applied Research that oversees the Georgia reactor, said he led the team that established the Iraqi facility.

After the 1986 Chernobyl disaster in Ukraine, Georgia's reactor was closed for safety improvements. The temporary shutdown became permanent after local environmentalists complained and the Soviet Union collapsed.

But the shutdown left Georgia with a troubling legacy.

Like other reactors of its generation, Georgia's used highly enriched uranium, a tempting target for would-be nuclear powers or terrorists hoping to build a bomb. Even the reactor's spent fuel, which was stored in a cooling pond, posed a danger, because such material can be refined into bomb ingredients.

The physics institute has never had any desire to retain the nuclear material, according to its director, Giorgi Kharadze.

But Kharadze, who wore a winter coat for an interview in his office heated by a small kerosene stove, said Georgia's economic collapse forced his country to seek outside help to dispose of the uranium.

During the Soviet era, Georgia periodically sent its spent fuel to a Russian nuclear center at Chelyabinsk in the Ural mountains of Siberia. The last trainload - 44 rod-shaped pieces of spent fuel - left for the center in March 1991.

Five extra rod-shaped pieces containing spent fuel could not be accommodated on the train and were left in the reactor's cooling pond. It seemed a minor complication at the time, but it later emerged as a major headache.

The collapse of the Soviet Union left the institute with the five rods, or nearly 2 pounds of spent fuel, and an additional 22 pounds of highly enriched uranium.

Georgia fell into civil war. After the fighting eased by 1994, the institute began again to whittle down its supply. It sent about 11 pounds of highly enriched uranium to Uzbekistan, which has a similar reactor. The material was shipped in August 1995 at a cost of about $6,000.

That still left Georgia with about 9.5 pounds of highly enriched uranium and the nearly 2 pounds of spent fuel.

Estimates vary about how much is needed to make a nuclear bomb. It depends on the skills of the bomb maker and the intended size of the explosion. One U.S. official said the material left in Georgia, while substantial, would not be enough to make a bomb. But some private experts said a proficient scientist could use it to do so.

``I would worry if it was in the hands of Iran or Iraq,'' said Thomas Cochran, senior scientist at the Natural Resources Defense Council, a private research group. ``They could amass a technically competent scientific team to fabricate a weapon with a yield of a kiloton.'' A kiloton is the equivalent of 1,000 tons of TNT.