In 1963, the Da Lat reactor, built by San Diego-based General Atomics, was supplied with U.S. bomb-grade uranium. In the waning days of the Vietnam War, the U.S. hastily shut down the reactor and pulled out the unused fuel. By the mid-1980s, the plant was operating again with Russian assistance and a new load of highly enriched uranium.
Although it does little cutting-edge research, the reactor helps train Vietnam's physicists and produces 30% of the nation's medical isotopes used in cancer treatment. It is also the pride of Vietnam's science establishment, employing a staff of 200.
But like many research reactors, security hardly meets Western standards.
At the front gate on a recent day, two young unarmed guards were on duty inside a glass-walled booth. A lone telephone sat on a desk to enable contact with a local police garrison.
Bieniawski's jaw dropped when he saw that the massive doors to the reactor containment building were held shut by a piece of old pipe jammed into the door handle. In interviews, Vietnamese officials said they didn't see any security problem.
"Vietnam is very safe," said Vuong Huu Tan, chairman of the Vietnam Atomic Energy Commission.
Nonetheless, Vietnam is cooperating, because it wants to build a nuclear power plant by 2020 and hopes its good intentions will help down the road. Tan has visited Westinghouse Electric to talk about reactors. The U.S. is also paying $80,000 for security upgrades in Da Lat, including alarms, sensors and improved communications, said Sarah Dickerson, another member of the team.
Bieniawski said the Vietnam mission was one of his most complex. It required approval by the prime minister, the highest level ever in a U.S. operation. It also needed separate deals with Russia for replacement fuel, eight technical licenses to cross borders with uranium, a nonproliferation statement by the parties and much more.
Such licenses are not simple one-page forms, but rather are complex scientific packages to show that the highly enriched uranium will not set off a dangerous "critical" event if, for example, an airplane carrying it crashes.
"You have to prove it with calculations," Bolshinsky said, sighing.
To end its use of bomb-grade uranium, the reactor had to be converted to operate on low-enriched uranium. A Russian factory designed and fabricated new fuel rods in only a few months. And as the mission drew near, Vietnamese officials were sticklers on details.
Among other things, the Vietnamese scientists insisted that Bieniawski prove that the reactor would work on the new fuel before they would allow the highly enriched uranium to leave the site. Wearing white and yellow lab coats, Bieniawski and Bolshinsky nervously watched control room gauges rise up to the full power of 500 kilowatts, giving Vietnamese scientists the assurance they wanted.
After a 36-hour test run, Nguyen Nhi Dien, director of the nuclear research institute in Da Lat, was smiling and shaking Bieniawski's hand, saying he hoped to continue cooperating with his team.
With sirens blaring, a convoy of 10 vehicles, including two local police wagons, a Vietnamese army platoon and a local firetruck, carried 35 unused fuel rods from the reactor site to a local airport. Bomb-grade uranium is at its most vulnerable on the road, Bieniawski said.
Along the way, hundreds of stunned Vietnamese civilians stopped on motor scooters to gawk, apparently wondering why a group of Westerners were in military-escorted vehicles.
The material was flown by helicopter to Ho Chi Minh City and then transferred to a Russian Ilyushin cargo jet for a long trip to Dimitrovgrad, Russia.
Vietnamese officials, unhappy about the presence of Americans at the former Tan Son Nhut base, told Bieniawski his team would have to leave as soon as they inspected the shipping casks aboard the Russian jet.
With a baseball cap and a grin, Bieniawski spent the next hour sweet-talking the Vietnamese, explaining it was important for him to verify the departure of the cargo plane. Soon, the team had been served tea and seated in an air-conditioned lounge to await the takeoff.
When the plane was ready to go, the Russian pilot opened his cockpit window and waved goodbye to the Americans.
As the wheels left the ground, a beaming Bieniawski turned to Bolshinsky: "One more country cleaned out."