福岛核电站将移除 1000 多根核燃料棒A task of extraordinary delicacy and danger is about to begin at Japan's Fukushima nuclear power station.日本福岛核电站将要进行一项非常精密且危险的任务。More than 1,000 fuel rod assemblies need to be removed from a building that was badly damaged following the tsunami Engineers are preparing to extract the first of more than 1,000 nuclear fuel rods from one of the wrecked reactor buildings. This is seen as an essential but risky step on the long road towards stabilising the site. The fuel rods are currently in a precarious（危险的） state in a storage pool in Unit 4. This building was badly damaged by an explosion in March 2011 following the Great Tohoku earthquake and tsunami. Moving the rods to safety is a high priority but has only become possible after months of repair work and planning. One senior official told me: "It's going to be very difficult but it has to happen." The fuel rods are four-metre long tubes containing pellets of uranium fuel and the fear is that some may have been damaged during the disaster. When the tsunami struck the Japanese coast, the flood swamped the diesel generators providing back up power to the reactors. Three of the reactors went into a state of partial meltdown. By coincidence, Unit 4 was undergoing maintenanc e, so all of its fuel rods were being stored. But the meltdown of a neighbouring reactor led to a build-up of hydrogen which is believed to have led to the explosion in Unit 4. In the days after the tsunami, there were fears that the blast had damaged Unit 4's storage pool and, in desperation, the authorities used helicopters and fire hoses to keep it filled with water. A guiding principle of nuclear safety is that the fuel is kept underwater at all times - contact with the air risks overheating and triggering a release that could spread contamination. So the operation to remove the rods will be painstaking. A senior official in the Ministry of Economy, Trade and Industry (METI) told me that the rods will be lifted out in batches of 22 and in casks filled with water. This will be done with a new crane, recently installed in the wrecked building, after the original one was destroyed.
