19 Mars 2015
March 18, 2015
It's been decided that several old nuclear reactors in Japan will be scrapped. The Mainichi Shimbun answers some common questions readers may have about the nuclear reactor decommissioning process.
Question: How do nuclear reactors get decommissioned?
Answer: First, as a preparatory step, decontamination work on nuclear plant buildings and equipment is carried out while letting spent nuclear fuel cool down. The nuclear fuel will then be removed from the reactors. Outer parts of the reactors get stripped down first, then the decommissioning work proceeds to the reactors' core, and finally, the reactor building is scrapped. The whole process -- from shutting down the operation of a nuclear reactor to the complete decommissioning -- takes almost 30 years.
Q: What are the major problems regarding decommissioning of a nuclear reactor?
A: One of the major problems as we enter the age where many of Japan's nuclear reactors are moving toward the end of their 40-year limit is the handling of the massive amount of radioactively contaminated debris and nuclear waste. The Ministry of Economy, Trade and Industry has estimated that a total of 537,000 metric tons of waste will be generated by scrapping one nuclear reactor that produces 1.1 million kilowatts of power. Of such reactors, the amount of radioactive waste would total about 13,000 tons, but the place to discard the nuclear waste has not been decided. Moreover, for highly contaminated equipment such as the reactor itself, there are no standard decommissioning policies.
Q: What will the nuclear plant operators do then?
A: Japan Atomic Power Co., which is carrying out the decommissioning work of its Tokai nuclear power station in Ibaraki Prefecture, has decided to bury 12,300 tons of nuclear waste that has very small levels of radioactive contamination in the ground at the plant. The company is currently negotiating with the municipal government about the plan. Chubu Electric Power Co. decided this month to temporarily store some 4,000 tons of radioactive waste generated by the No. 1 and 2 reactors of the Hamaoka Nuclear Power Station in Shizuoka Prefecture, currently being decommissioned, on its premises. The decision was made as the company has been unable to come up with a clear plan on where to put the nuclear waste, though it initially sought to pick a permanent disposal site before the decommissioning process began.
Fukui Gov. Issei Nishikawa has urged utilities to move the radioactive waste away from the compounds of the nuclear plants in the prefecture, saying that the grounds should become vacant land after the decommissioning work is completed.
Q: What other tasks are involved in decommissioning nuclear reactors?
A: While nuclear plant operators have to move spent nuclear fuel kept in pools away from the plant before the decommissioning work begins, they don't seem to be able to find a place that will accept the waste. There are no prospects as to when the original destination of the spent nuclear fuel, Rokkasho nuclear fuel reprocessing plant in Aomori Prefecture, will resume its operations, and all of the country's spent fuel pools are getting close to full.
Utilities are considering storing spent fuel in air-cooled casks outside plant premises, but such a project has made little progress as companies face opposition from local residents. (Answers by Yui Shuzo, Science & Environment News Department)
March 18, 2015(Mainichi Japan)