[Kaneman]

The commitment to Monju is rooted in the way Japan has sold its nuclear program to local communities, experts say. In persuading towns and villages to provide land for nuclear power stations, Japan has promised that the spent nuclear fuel — which remains highly radioactive for years — will not be stored permanently on site, but used as fresh fuel for the nuclear fuel cycle.

Miwako Ogiso, part of a Fukui Prefecture group against nuclear power, calls the Monju project “Japan's most dangerous reactor.” It has a history of safety problems and lies on an active fault.

Giving up on any part of the fuel cycle would mean the government would have to find communities willing to become the final resting ground for the spent fuel.

“Of course, no community would accept that, and suddenly Japan’s entire nuclear program would become unviable,” said Keiji Kobayashi, a retired fast-breeder reactor expert formerly at the Kyoto University Research Reactor Institute.

But the technology comes with risks. Instead of water, which is used in commercial nuclear reactors, the prototype reactor uses 1,600 tons of liquid sodium, a hazardous material that reacts fiercely with water and air, to cool its fuel. The presence of an estimated 1.4 tons of highly toxic plutonium fuel at the reactor makes it more dangerous than light-water reactors, which use mainly uranium fuel, critics charge.

Meanwhile, other parts of Japan’s nuclear fuel cycle are also unraveling. The full opening of a nuclear fuel reprocessing plant in the village of Rokkasho, in Aomori Prefecture, has been delayed countless times, with more than $20 billion invested in the project.

Still, work continues to restart the Monju plant. In October, engineers used a crane to try to lift up the device, adding about 220 pounds of force a time. After 24 attempts, they gave up, fearful of the strains on the entire reactor.

Since mid-May, workers have been prepping for a different strategy, clearing the reactor’s lid of various instruments. As early as next week, workers will try to remove the device by dismantling a part of the vessel’s lid with it.

Workers face other dangers in fixing the plant. The reactor contains argon gas, which helps keep the sodium from burning but is a dangerous asphyxiant in confined spaces. And should the device fall farther into the reactor vessel, the damage could be substantial.

The atomic energy agency hopes the extraction will be complete by the end of the month. The agency says it will conduct extensive safety checks, and bolster its earthquake and tsunami defenses, before the reactor is eventually restarted.

“The device will definitely come out this time,” said Toshikazu Takeda, director at the University of Fukui Research Institute of Nuclear Engineering, and head of a government panel that approved the latest repair plans. He said that engineers had recreated removal procedures at a lab and perfected their handling of the crane that will lift the device from the reactor vessel.

Once removed, the device will be checked thoroughly for missing parts or damage, he said. The liquid sodium coolant, heated to almost 400 degrees Fahrenheit, makes it impossible to check fully for any damage the device may have caused to the reactor vessel, however.

Still, Mr. Takeda said he hoped to see Monju complete safety checks and prepare for a restart within a year.

“Japan needs the nuclear fuel cycle,” he said, because supplies of fuels will not last forever. “Uranium will last less than a hundred years. Plutonium will last over a thousand.”