Dr. Tsubokura's Radiation Lecture Vol.87
Author: Masaharu Tsubokura
Editors: Akihiko Ozaki M.D., Yuki Senoo
173. Radioactive wastes are handled differently according to their concentration
A variety of radioactive wastes are produced from many facilities that process radioactive substances, such as nuclear power plants, nuclear research institutes, and hospitals that use radiopharmaceuticals. Although the amount of radioactive wastes produced in these facilities is less than 1 / 10,000 of the nonradioactive wastes—such as general and industrial waste—nuclear waste needs to be dealt with appropriately depending on the type and concentration of radioactive substances.
Radioactive wastes produced by nuclear facilities are roughly classified into two categories: “high-level radioactive wastes,” which are the liquid form of radioactive residue produced in the reprocessing of uranium and plutonium in spent nuclear fuel, and “low-level radioactive wastes,” which are the broad group of radioactive wastes produced in nuclear power plant operations that are not spent nuclear fuel. Additionally, “low-level radioactive wastes” include other radioactive wastes, such as concrete and pipes from research facility buildings, paper and cloth, rubber gloves, wastewater used in the washing process, and experimental equipment.
However, these classifications are only used to distinguish the radioactive waste generated during the operation of nuclear facilities. In August 2011, the Japanese government specially enacted a law entitled “Act on Special Measures concerning the Handling of Environment Pollution by Radioactive Materials Discharged by the NPS Accident Associated with the Tohoku District - Off the Pacific Ocean Earthquake That Occurred on March 11, 2011” (hereafter the “Act on Special Measures”), thereby stipulating a system to decontaminate and handle the waste that was released into the environment by the Fukushima nuclear accident. According to the Act on Special Measures, radioactive substances released from the nuclear disaster in Fukushima, including ash and sewage sludge, are classified as “designated wastes” and “wastes in the countermeasure areas.”
174. Reprocessing of spent nuclear fuels is conducted overseas
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.
Nuclear reprocessing of spent nuclear fuel is not conducted in Japan, but reprocessing companies in Great Britain and France do such jobs for our country. After reprocessing, the processed high-level radioactive wastes are sent back to Japan by boat with the recycled uranium and plutonium.
The liquid residue produced after reprocessing spent fuel is then solidified by mixing with melted glass and is transported in a particular container. The time required for the radioactivity of liquid radioactive residues to reach safe levels is estimated to be at least 10,000 years. In Japan, the law stipulates that radioactive wastes be isolated and stored in an inaccessible area buried more than 300 meters underground.
This method of handling radioactive wastes is called geological disposal. This project has been under way step by step, but none of the geological disposal facilities in the world meet the ideal criteria for safely storing radioactive wastes. In Japan, high-level radioactive wastes are temporarily stored for cooling at the High-Level Radioactive Waste Storage Management Center, located in the village Rokkasho in Aomori Prefecture.
The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, 6th and 13th May 2018 was reproduced for MRIC Global under the author's permission.