The perils of Japan's huge, lightly guarded plutonium stockpile

But in reality the plant 700 kilometers north of Tokyo is one of the world’s newest, largest and most controversial production facilities for a nuclear explosive material. The factory’s private owners said three months ago that after several decades of construction, it will be ready to open in October, as part of a government-supported effort to create special fuel for the country’s future nuclear power plants.

Once it’s running, sometime after October, the plant will produce thousands of gallon-sized steel canisters containing a flour-like mixture of waste uranium and plutonium. In theory, the plutonium is capable of providing the fuel for a huge nuclear arsenal, in a country that protects its nuclear plants with unarmed guards and has resisted U.S. pleas to upgrade security…

A six-and-a-half pound lump of plutonium— enough to make a weapon — is the size of a grapefruit. The point, critics say, is that a thermos full of the metal in the wrong hands could produce a devastating terror attack.