Decontamination in Decommissioning of Nuclear Facilities

Decontamination is likely to be one of the most important procedures in decommissioning of nuclear power plants. Nuclear power plants contain two types of radioactive materials after some period of operation; one is radioactive material activated directly by neutrons such as in-core material, and the other is material such as primary pipes of which the surface is contaminated by radioactive elements. The inventory of the former radioactivities is much higher than that of the latter, whereas the total volume of the former is much smaller that of the latter. These radioactive materials cause troubles of the increase in radiation exposures of workers during the disassembly of the plants and of increasing the volumes of radioactive wastes generated in the decommissioning. It is predicted in one of the estimation 1) that the decommissioning of a 1200MW PWR generates approximately 14000 tons of radioactive wastes comprising of metals and concretes with one year of storage after 40 years of operation, of which the 20 percent is the activated material and the others the contaminated. Most part of the radioactive concrete wastes has rather low activities