Dr. Tsubokura's Radiation Lecture Vol.88
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
175. Issues surrounding management and disposal of high-level radioactive wastes
Radioactive wastes produced by nuclear facilities are classified into two categories: high-level radioactive wastes and low-level radioactive wastes. A high-level radioactive waste is the liquid form of radioactive residue produced in the reprocessing of uranium and plutonium in spent nuclear fuel. This type of radioactive waste is solidified by mixing it with the melted glass; it is then transported and managed in a special container.
The management of high-level radioactive wastes has been a common problem for all countries operating nuclear power plants, not just Japan. Many countries are attempting to isolate radioactive wastes deep underground in a safe, inaccessible area, such as a stable rock area. This method of radioactive waste disposal is called geological disposal. To safely accomplish geographical disposal of radioactive wastes, it is necessary to select an appropriate disposal site and build a special facility. However, the process for planning and execution requires at least several decades, and the advancement of this process varies greatly from country to country.
Two Scandinavian countries, Finland and Sweden, have made the most outstanding advancements in geological disposal. These two countries have already established disposal sites within their territories. Furthermore, Finland has begun construction of the world’s first geological disposal site.
On the other hand, as in the United States, the United Kingdom, and Canada, Japan has not determined the location of the final disposal site, although radioactive waste is temporarily stored for cooling at Rokkasho Village in Aomori Prefecture.
176. Different methods of management and disposal for each type of radioactive waste
Radioactive wastes produced by nuclear facilities are classified as high-level radioactive waste or low-level radioactive waste. As explained in the previous article, a high-level radioactive waste is the liquid form of radioactive residue produced in the reprocessing of uranium and plutonium in spent nuclear fuel.
On the other hand, low-level radioactive wastes refer to all radioactive wastes that are not high-level radioactive wastes. Therefore, low-level radioactive wastes have a wide range of radioactivity; this category includes those with low levels of contamination, such as power plant concrete and metal, used paper towels, and working clothes, to those with relatively high levels of radioactivity, such as used control rods.
Therefore, low-level radioactive waste is handled differently depending on its type. Solid forms of radioactive wastes, such as paper and cloth, are burned and compressed, while liquid waste is packed in drums after being concentrated and solidified with cement. In Japan, these drums are stored in a shallow underground hole surrounded by concrete at the disposal facility located in Rokkasho Village, Aomori Prefecture.
In contrast, the management of high-level radioactive waste has not been fixed. At present, a discussion is underway with regard to whether high-level radioactive waste should be buried deeper than 70 meters below ground, but no action has been taken yet.
The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 20th and 27th May 2018 was reproduced for MRIC Global under the author's permission.