The Mainichi answers common questions readers may have about how disaster-response workers plan to remove melted fuel from the disaster-stricken Fukushima No. 1 Nuclear Power Plant.
Question: What methods are being considered for removing the fuel?
Answer: Innovation will be needed in order to avoid exposing people to radiation, due to the high levels of radiation released from the fuel. One method under consideration is to fill the containment vessels holding the fuel with water, since water has radiation-blocking properties.
Q: Aren't the containment vessels ruptured?
A: Just like you can't fill a cup with water if it has a hole in it, the water-filling method won't work if the containment vessels are ruptured. If they are, then another possible method is removing the fuel from the air.
Q: Which way is better?
A: Both have advantages and disadvantages. The water method could require finding and patching holes in the containment vessels. The air method wouldn't need this, but could cause dust and other particles containing radiation to be released. The national government and plant owner Tokyo Electric Power Co. (TEPCO) will discuss as early as this summer about these two plans.
Q: What is the fuel like now?
A: At the time of the meltdown, the reactors at the plant were heated to over 2,000 degrees Celsius. The melted fuel is thought to have mixed with equipment in the plant, concrete and other materials, and to have cooled to a rock-like state. It will have to be cut out and removed.
Q: How will the fuel be cut loose?
A: The plan is to use a remotely-controlled robot. However, high-tech electronics using semiconductors are easily broken by radiation. There are ideas to make the robot use hydraulics or springs for its movement, to make it resistant to the radiation. Robot technology will be the key to a successful decommissioning of the reactors. (Answers by Mirai Nagira, Science & Environment News Department)