TOKAI, Japan — Wedged in a corner of a pine-scented, campus-like research center here is the so-called Fast Critical Assembly, which — except for a squat reactor containment dome — looks more like a suburban elementary school than a nuclear laboratory handling some of the world’s most dangerous materials.
About a dozen researchers work at the FCA, which began operations in 1967. They study plutonium and weapons-grade uranium, the principal building blocks of nuclear arms, to design fuel for Japan’s future breeder reactors, a key to the country’s ambition to increase its energy independence.
But their work will soon be altered, because Japan — after years of resistance — has finally agreed to return its stock of plutonium at the FCA to the United States, in the form of 5,451 square metal wafers, according to officials in both countries. The agreement is to be announced at a U.S.-led international summit to promote the security of such fissile materials, beginning March 24 in the Netherlands.
The Obama administration will hail the deal as a crucial step in its global campaign to ensure that terrorists cannot obtain such explosive materials, authorities say. U.S. officials say they have been worried the materials here have been casually guarded, and are concerned that that there is no federal standard requiring workers at such plants to be subjected to formal, detailed background checks like those for nuclear workers in the United States.
Some nonproliferation experts say the withdrawal of the explosives from Japan, while a step in the right direction, represents little more than window dressing, however, since the country has 9.3 metric tons of additional plutonium stored at other locations domestically and plans to start producing more at its new Rokkasho factory later this year.
“The first place the Japanese would go if they wanted to make nuclear weapons would be to [this] stockpile, because it’s the best plutonium they have for making weapons,” said Thomas Cochran, a Natural Resources Defense Council physicist who has spent much of his career opposing breeder reactor programs like Japan’s. “But they have plenty of other plutonium. If they wanted nuclear weapons, this [shipment] wouldn’t reduce the risk of [their] acquiring them.”
Nor would the return of the materials, by itself, reduce the risk of terrorists stealing similar materials stored elsewhere in Japan, including at Rokkasho, Cochran said.
About 50 researchers and staff presently work at the research facility here, formally known as the Tokai Research and Development Center and located about 70 miles north of Tokyo. It includes a storage building holding a total of 730 pounds of plutonium and 660 pounds of weapons grade uranium. More than 90 percent of the plutonium is the isotope plutonium-239, the kind favored by professional nuclear weapons designers.
Both the plutonium and the weapons grade uranium were provided by the United States and Britain to Japan’s civil nuclear program starting in the 1960s. And the Obama administration has been asking for the materials since before the president convened the first international Nuclear Security Summit in 2010, partly because U.S. officials were alarmed by how casually the explosives have been protected there.
The stocks of both explosive materials here could provide sufficient fuel for roughly 375 bombs with the explosive force of 20 kilotons, or 20,000 tons of TNT. That was the power of the bomb that exploded over Nagasaki in 1945.
Like the security guards stationed at most Japanese nuclear facilities, none at the Fast Critical Assembly facility are armed, although local police are stationed nearby in the larger research campus. Japanese officials have acknowledged to visiting Westerners that if the guards ever faced attacking terrorists, their instructions are to flee.
To U.S. officials, this approach is almost unthinkable — as if the U.S. had decided it couldn’t or wouldn’t post armed guards with security clearances at the sites in Texas, New Mexico, and California where most of its bomb fuels are stored.
With the encouragement of the United States, Japan since 1978 has shut down a few research reactors that used such risky fissile fuels, sometimes converting them to use low-enriched uranium. But Japanese officials have until now resisted relinquishing the fuel at the Tokai facility, the largest research center of its kind in the world, because it will be difficult to replace.
Tsuyoshi Yamane, a silver-haired senior engineer at the site, told the Center for Public Integrity during a visit in November that there has been increasing “pressure imposed” by the international community, including the United States, for Tokai to halt its work with nuclear explosives.
He acknowledged that the facility is “very, very old” and that a room adjacent to the reactor in which fuel is assembled had cracked during the March 2011 earthquake. “Luckily, that was a day when there was no actual test or experimenting,” he said.
But Yamane said then that the fuel development done at Tokai could not be conducted using other, less dangerous materials. “The research groups who work here have said they need to use the system as it is, in order to carry out experiments and tests,” he said.
Two-thirds of that research, he said, is aimed at designing the most efficient fuels for fast breeders, a type of reactor that both consumes and produces plutonium. The United States, France and Britain all launched commercial fast breeder programs, only to abandon them in the 1980s and 1990s. Only Japan, Russia and India are still developing fast breeder reactors.