By Arjun Makhijani [1]

When Greenpeace revealed last September that the U.S. Energy Department had been secretly supplying Japan with technical know-how on producing weapons-grade plutonium, it was just one in a series of nuclear revelations that have shocked the Japanese public and raised questions about what Japan’s nuclear weapons policy really is.

In August, a 25-year-old Japanese Foreign Ministry document was leaked to the Mainichi Shimbum, a large daily newspaper. Written in 1969, when Japan was considering the Nuclear Nonproliferation Treaty (NPT), the document argued that the country did not need nuclear weapons “for the time being,” but that it should “keep the economic and technical potential for the production of nuclear weapons, while seeing to it that Japan will not be interfered with in this regard.” The Japanese government admitted the authenticity of the document, but promptly denied that the policy had ever been adopted.

Although Japan has the technological base, materials, and delivery systems to build a nuclear arsenal, in its public statements the government has consistently disavowed any nuclear ambitions. Japanese officials point to the bombing of Hiroshima and Nagasaki to explain their country’s “nuclear allergy,'” which they say is so strong that Japan could never acquire nuclear weapons. In 1968, Prime Minister Eisaku Sato declared that Japan would not produce, not introduce, and not possess nuclear weapons.

In addition, Japan’s constitution would seem on its face to bar the maintenance of any military force. Article 9 states that “land, sea, and air forces as well as other war potential will never be maintained,” and pledges further that Japan will never use war or the threat of force “as means of settling international disputes.”

Over the years, however, the Japanese government has demonstrated considerable flexibility in interpreting the mission of its “self-defense” forces, so much so that defense forces could conceivably include nuclear weapons. Although Japan relies on the U.S. “nuclear umbrella,” the 1969 document indicated that indicated that the acquisition of nuclear weapons should be governed by a “cost-benefit calculation” that weighs the desirability of relying on the United States against creating an indigenous arsenal.

Despite the government’s protestations, there is more recent evidence that Japan’s Foreign Ministry continues to favor nuclear weapons. Last June , the ministry prepared a document for the then-coalition government to send to the World Court stating that the use of nuclear weapons in war was not necessarily illegal. (The World Court is considering two requests for an opinion on the legality of using nuclear weapons, one from the World Health Organization and a broader on from the United Nations General Assembly.)

In the end the government did not forward that part of the ministry’s statement to the World Court because its disclosure caused a public furor. Still, the Foreign Ministry’s opinion seemed both to reaffirm Japan’s reliance on U.S. nuclear weapons and to indicate that the acquisition of nuclear weapons option may not be entirely closed. Any active Japanese policy that keeps the nuclear option open would violate the spirit of the NPT in the same way that the failure of the nuclear weapons powers to create a plan and a timetable for disarmament violates it.

The unhappy history of Japanese militarism in Asia continues to arouse suspicions on the part of it neighbors, especially North and South Korea, and even at home. In January, a Japanese expert on plutonium policy, Jinzaburo Takagi, said Japan “has failed on every possible occasion to totally deny the ‘benefits’ of having nuclear weapons.” The Japanese government’s protestations citing the tragic events of Hiroshima and Nagasaki are no longer enough. It is clear that the Japanese government internally debated the nuclear weapons option between 1969 and 1976, when it signed the NPT and took on a solemn obligation not to acquire nuclear weapons. If it did not make a secret decision then to maintain the capability for a nuclear option, it has nothing to hide. But a failure to make its record public only heightens suspicions that Japan has continued to keep the nuclear option alive.

Japan also continues to extract plutonium from civilian spent fuel and to accumulate additional stocks as Britain and France, under contract, reprocess some of Japan’s spent fuel. The approximately 11 metric tons accumulated by the end of 1993 greatly exceed Japan’s capacity to use them as reactor fuel in the near future. Despite many statements to the contrary by Japanese officials, these stocks could be used to make nuclear weapons. The United States, in turn, does nothing to prevent Japan from accumulating large stocks of plutonium, even though it legally could have stopped shipments from France to Japan because some of the plutonium was made from uranium of U.S. origin.

Given the dangers of proliferation and the need to deal even-handedly with all countries in the enforcement of the NPT, the Clinton administration should bar further plutonium shipments from Britain or France until Japan publishes all documents related to its nuclear weapons policy.


  1. First published as “What ‘Non-Nuclear’ Japan Is Not Telling the World and How Tokyo Keeps Its Options Open,” The Washington Post, April 2, 1995, p. C2. This article was adapted from one in the January/February 1995 issue of the Bulletin of the Atomic Scientists. Arjun Makhijani is president of the Institute for Energy and Environmental Research in Takoma Park, Maryland. ↩ Return