NO NUKES: People take part in an anti-nuclear rally in Tokyo on March 9, ahead of the third anniversary of the Fukushima nuclear disaster (XINHUA/AFP)
More than one month ago, Japan's Kyodo News reported that the United States has been pressing Japan to return 331 kg of mostly weapon-grade plutonium that was received from the United States and Britain for fast reactor research during the Cold War.
Despite this recent attention, in actuality, Washington has been urging Tokyo to return the nuclear materials as soon as possible since at least the Washington Nuclear Security Summit in 2010. However, Japan has been reluctant to comply, claiming that the plutonium has been used in fuel assemblies in its research. Only recently did the Japanese Government attempt a bargain before the Hague Nuclear Security Summit, scheduled for March 24-25, with the United States on the issue.
In his speech in Prague in 2009, U.S. President Barack Obama announced a goal to secure all vulnerable nuclear materials around the world within four years. The Obama administration's resolution that Japan must return the plutonium is aimed at integrating the issue into the process of the Nuclear Security Summit.
Plutonium and highly enriched uranium are the basic materials needed to build a nuclear bomb. Highly enriched uranium can be relatively easily used to make gun-type nuclear weapons while plutonium can be used to make more sophisticated implosion-type nuclear weapons. Highly enriched uranium is widely used in scientific research and isotope production; thus, many non-nuclear-weapon states have a limited supply for such purposes. But since plutonium needs to be exacted from spent fuel, few countries own separated plutonium for civilian use.
For the above reasons, the reduction measures proposed by the first two nuclear security summits mainly focused on highly enriched uranium for civilian purposes, such as converting reactors from using highly enriched uranium fuel to using low-enriched uranium and voluntarily returning the highly enriched uranium. Thus far, those measures have been well implemented and much progress has been made in reducing highly enriched uranium. Against this backdrop, the United States wants all countries to reduce their surplus separated civilian plutonium gradually after the Hague Nuclear Security Summit following the highly enriched uranium reduction mode. Washington's urging Japan to return of plutonium also aimed to make Japan an example for other countries.
The key topic of nuclear security summits is, predictably, keeping nuclear materials out of terrorists' hands. For Japan, the international community worries that the country might produce nuclear weapons and damage the international nuclear nonproliferation regime. Kyodo News cited an unnamed insider of the Abe cabinet as saying that Japan's agreeing to return the plutonium is intended to eliminate international concerns on Japan's military expansion. However, the approximate amount of 300 kg separated plutonium exported to Japan is merely a drop in the bucket of Japan's own separated plutonium storage. Given Japan's strong capacity for nuclear enrichment and reprocessing as well as the growing right-wing support for Japan to produce its own nuclear weapons, Japan must do more to win the trust of the international community.
Japan is the only non-nuclear country that owns a large quantity of separated civilian plutonium. For many years, under the guise of fast reactor research, it produced plutonium after purchasing reprocessing services from Britain and France. By the end of 2011, Japan had produced 44.3 tons of separated plutonium, among which 9.3 tons are stored within Japan while the rest is deposited in Britain and France.
Due to differences in the burn up of nuclear fuel in the reactor, the percentages of the isotope plutonium-240 in the plutonium extracted differ. Plutonium is graded as either reactor-grade or weapon-grade depending on the percentage of the isotope plutonium-240. Currently, the plutonium Japan possesses is mainly reactor-grade one. However, U.S. tests in the 1960s showed that any grade of plutonium can be used to make nuclear weapons. In addition, Japan's advanced technology means it is likely able to produce nuclear weapons with reactor-grade plutonium. Therefore, the international community is still doubtful of the intentions behind Japan's large plutonium stockpile.