WASHINGTON - As Viet Cong and North Vietnamese army soldiers converged on a city north of Saigon in March 1975, two engineers from Idaho were sent by Washington on an ill-fated secret mission to retrieve some uranium fuel and a small container of plutonium at a U.S.-built nuclear reactor there, the Department of Energy disclosed yesterday.
With sniper bullets whizzing around them, the engineers used a forklift and shipping containers hurriedly flown into the country to pack up the fuel and get it to Saigon. But they mistakenly retrieved a small container of polonium - a radioactive material unusable in weaponry - and left behind the much more dangerous plutonium, which then fell into Communist hands.
Although the amount of plutonium was just 80 grams - or about one-hundredth the amount needed to fashion a crude nuclear weapon - such a loss is ordinarily treated as a significant risk to human health and a major U.S. political concern.
Not until four years later did Hanford researchers in Washington state test the retrieved material and find it was polonium.
And it wasn't until last fall that an Energy Department official stumbled across records on the case.
The State Department has since raised the matter with both the Vietnamese government and the International Atomic Energy Agency, an international watchdog group that keeps tabs on sensitive nuclear materials. IAEA officials told Washington last week that they will send inspectors to the reactor site in the city of Dalat, 180 miles north of Saigon, next month.
The plutonium is believed to still be there.
Energy Secretary Hazel O'Leary disclosed the matter yesterday in a final effort to release formerly secret DOE information before she leaves office on Monday.
At her news conference, she also described new details about potential health hazards at U.S. storage sites for highly enriched uranium, another nuclear-weapons ingredient; revealed that 13 more underground nuclear blasts pumped radiation into the atmosphere than were previously known; and said DOE has begun declassifying up to 6,500 films of nuclear blasts conducted in the atmosphere or the ocean.
"Openness has advanced public understanding and earned us . . . public trust," O'Leary said as she released a new draft regulation barring the future classification of nuclear-weapons data relating to environmental protection, safety, and the health concerns of those who live near DOE facilities.
Her department nonetheless confronts a daunting Cold War legacy of 285 million pages of classified material, of which it declassified just 1.9 million last year.
According to Roger Heusser, deputy director of DOE's declassification office, Washington sent both the plutonium and nuclear fuel to Dalat in 1962 to be used in a research reactor constructed under the notorious Eisenhower-era Atoms for Peace Program - designed to help spread the gospel of cheap atomic power around the globe.
The facility had come under fire during the Tet offensive in January 1968, and one of its Vietnamese operators had been executed. But it was not until 1975 that Washington became alarmed.
The retrieval operation was completed just hours before Dalat fell to the Viet Cong. But the crate containing the supposed plutonium was not checked until 1979, after the two engineers had received awards for valor in wartime. Washington never followed up the discovery and failed to give proper notice to the IAEA of the slip-up, Heusser said.
Also Wednesday, DOE released a report detailing significant environmental or safety shortcomings at U.S. sites where the government stockpiles highly enriched uranium.
The department said the facilities show 155 conditions or weaknesses "that could result in the exposure of workers or the public to radiation."
In most cases, the health or safety threats are confined to workers on site, but in a few cases the shortcomings also "could adversely affect the public" if not corrected, said the report released by O'Leary. Some could take years to correct.
The Energy Department has 250 metric tons of highly enriched uranium, used in weapons, at 22 sites, about three-fourths of it at the Oak Ridge complex in Tennessee. Information from Associated Press is included in this report.