The N Word.(International Edition)(nuclear proliferation in Japan)

Byline: Takashi Yokota

Why Japan won't go nuclear.

North Korea's recent nuclear test has spawned many nightmare scenarios, including the possibility that pacifist Japan will go nuclear, triggering a new arms race. Both U.S. Secretary of State Hillary Clinton and Defense Secretary Robert Gates have warned of just that possibility, and on May 31 former secretary of state Henry Kissinger said that unless Beijing reins in Pyongyang, it should expect to "live in an Asia in which South Korea and Japan have nuclear weapons."

It sounds plausible. After all, Japan is one of the only great powers that doesn't already boast its own nuclear deterrent. Though Tokyo has officially vowed never to possess, build or even allow nuclear weapons onto its territory--promises born from Hiroshima and the pacifist constitution imposed on Japan by its U.S. occupiers after the war--some big-name Tokyo politicians have questioned that stance in recent years. In April, Goji Sakamoto, a lawmaker from the ruling Liberal Democratic Party, said that Japan should at least "threaten" to go nuclear. Shinzo Abe, who was prime minister from 2006 to 2007, once reportedly told a room full of college students that possessing nukes wouldn't violate Japan's constitution as long as the arsenal was "small in scale." And after Pyongyang's first nuclear test in 2006, senior LDP member Shoichi Nakagawa and Prime Minister Taro Aso (then foreign minister) called for public debate on the question.

Yet this is all just rhetoric. For one thing, despite North Korea's threats and China's growing military and political power, the Japanese people remain dead set against building nuclear weapons. Polls conducted over the past three years show that less than 20 percent of the public currently says it favors possessing such a deterrent.

For another, Japan--a crowded island nation--lacks the space to test a bomb. Japan has large stockpiles of plutonium for its nuclear-energy industry. But plutonium-type bombs require physical testing to verify their efficacy. (Uranium bombs are considerably simpler and so may not need physical testing, but Japan doesn't have the weapons-grade uranium to make such a device.) While some experts argue that Japan could test a plutonium weapon by detonating it underground, others--including former defense chief Shigeru Ishiba--insist that there is simply nowhere to do so in such a densely populated nation. Simulations would not be sufficient; those only work after at least one actual ...