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.