Japan owns nearly 50 tons of separated plutonium. That is enough for over 5,000 nuclear weapons. Yet Japan has no feasible peaceful use for most of this material.
This raises an obvious question: How did a country that forswears nuclear arms come to possess more weapons-usable plutonium than most countries that do have nuclear arsenals?
Some argue it is the unforeseen consequence of unexpected events, such as the failure of Japan's experimental Monju breeder reactor, or the Fukushima accident that compelled Japan to shut down traditional nuclear power plants.
Indeed, Kyodo News quoted a former U.S. government official last year making such a claim. He asserted that "The accumulation of plutonium by Japan was not anticipated by Congress or any agency of the U.S. government," when Washington in 1988 gave Japan 30-year approval to separate plutonium from spent fuel originally supplied by the United States or irradiated in U.S.-technology reactors.
But that is false.
Japan's massive accumulation of nuclear weapons-usable plutonium was foreseen three decades ago.
In testimony submitted to the U.S. Congress in March 1988, and published that year, Dr. Milton Hoenig of the Nuclear Control Institute -- where I worked at the time -- documented how Japan's planned separation of plutonium from spent fuel greatly exceeded its planned recycling of such plutonium in fresh fuel. The inevitable result, he predicted, was that Japan would accumulate enormous amounts of separated plutonium.
As his testimony detailed: "By the end of the year 2017...according to present plans, about 255 metric tons of Japanese-produced plutonium will have been separated in reprocessing plants in Japan and Europe. The announced plans of Japan demand the use of some 130 metric tons of separated plutonium as reactor fuel through the year 2017, mainly in light-water reactors in a commercial program to begin in 1997."
Thus, he concluded, Japan's declared plans would yield 125 tons of surplus plutonium by 2017.
Subsequent unforeseen events did not cause Japan's huge plutonium stockpile, as the U.S. official claimed, but actually reduced it somewhat. Notably, Japan has postponed the commercial operation of its huge Rokkasho reprocessing plant, which could separate another eight tons of plutonium each year.
The hard truth is that creation of a plutonium surplus was not an accident but the inevitable consequence of Japanese nuclear policy that the U.S. government acquiesced to in 1988.
Why did Japan intentionally acquire a stockpile of plutonium sufficient for thousands of nuclear weapons? Neighboring countries suspect it is to provide Japan the option of quickly assembling a large nuclear arsenal. Not surprisingly, both China and South Korea are now pursuing options to separate more plutonium from their own spent nuclear fuel.
Three urgent steps are necessary to avert this latent regional arms race. First, Japan should terminate its Rokkasho plant, which is an economic, environmental, and security disaster. The last thing Japan needs is more surplus plutonium.
Second, the United States and Japan should seize the opportunity of their expiring 1988 deal to renegotiate new terms restricting plutonium separation, which could also serve as a model for ongoing U.S.-South Korea nuclear negotiations.
Finally, innovative thinking is needed to shrink Japan's plutonium stockpile. In light of the worldwide failure of breeder reactors, and post-Fukushima constraints on traditional reactors, most of Japan's plutonium will never become fuel. Instead, it should be disposed of as waste. The U.S. government has recently made a similar decision, abandoning plans to use recovered weapons plutonium in fuel and instead intending to bury it.
U.S.-Japan collaboration to dispose of surplus plutonium in a safe, secure and economical manner could help make up for the misguided bilateral decisions that created this problem 30 years ago.
(Alan J. Kuperman is associate professor and coordinator of the Nuclear Proliferation Prevention Project -- www.NPPP.org -- at the Lyndon B. Johnson School of Public Affairs, University of Texas at Austin.)