WASHINGTON -- When 27 U.S. nuclear technicians landed six weeks ago in Ust-Kamenogorsk, Kazakhstan, they saw that a large cache of bomb-grade uranium there had been stored without any of the high-tech safeguards commonplace at American facilities, according to U.S. officials.


A long warehouse, containing enough uranium to be used in 20 to 25 nuclear weapons, was located in the middle of a sprawling nuclear and metallurgical factory employing more than 14,000 people. But no chemical assays or radiation sensors were used to account for, or safeguard, the material -- instead, its presence or absence was simply noted by hand in record books.


"The whole system was run by paper," said Alex Riedy, a nuclear engineer with Martin Marietta Energy Systems, a contractor to the Department of Energy. Riedy helped direct a successful U.S. effort to repackage the uranium so it could be shipped out of Kazakhstan to thwart its potential theft by nuclear terrorists or other nations.


Defense Secretary William Perry on Wednesday hailed the previously secret operation as "a success story in counter-proliferation." Last weekend more than 600 kilograms of highly enriched uranium originally produced in the Soviet Union was shipped from Kazakhstan to Dover Air Force Base in Delaware in two C-5 military cargo planes and then trucked to Oak Ridge National Laboratory in Tennessee.


Perry and other officials did not say which nations Washington had feared would obtain the material, which was only mildly radioactive and had been stored by Kazakhstan nuclear authorities in readily transportable canisters. But a senior defense official said the suspect countries were located near Kazakhstan.


To help repackage the nuclear material into 1,400 shipping containers the size of oil cans, Riedy said he and his colleagues had to set up their own laboratory in a large, unheated room at the Ulba Metallurgical Plant that was considered unusually secure because it had double-locked doors and a motion sensor. The room had been used to store Kazakhstan coins minted at the factory.


Because the facility had been contaminated by an industrial explosion in 1990, U.S. technicians took pains to assess the health risks during a scouting trip. They also brought along respirators, which offered more protection than the cotton masks worn at the plant.


Officials involved in the operation said it went more smoothly inside Kazakhstan than it did outside the country.


They said, for example, that the Pentagon had difficulty winning over flight rights from various countries for the C-5s, which had been declared to be carrying hazardous cargoes. Tennessee authorities also initially opposed the idea of storing it, and Secretary of Energy Hazel O'Leary sought to ease public concern in Tennessee by pointing out that the material is not nuclear waste, but "non-irradiated material."


During their day off each week, the technicians toured the area around the plant and discovered that two nearby orphanages and a home for pensioners desperately needed food and winter clothing.


Without disclosing exactly what they were up to, they solicited $1,800 in donations from friends and family around Oak Ridge, and persuaded the Pentagon to ship in almost 18,200 kilograms of aid on one of the C-5s.