Abstract
After low-level liquid radioactive wastes generated from nuclear power stations are asphalt-solidified and emplaced in drums, they are entombed in burial disposal facilities. Those radioactive wastes contain chemicals such as boron, which can cause environmental impacts aside from those of radionuclides. The leaching characteristics of radionuclides from asphalt solidified waste have been discussed in many reports. However, no study case for boron has been reported. For this study, leaching tests of 1000 days were conducted to comply with the IAEA (International Atomic Energy Agency) test method used for simulated asphalt solidified wastes. Results confirmed the leaching characteristics of chemical substances such as boron and radionuclides. Furthermore, surface and cross-sectional surface observations were conducted over time using SEM (Scanning Electron Microscope) and other analytical modes. Results revealed leaching characteristics and cross-sectional surface observations for leaching of substances from inside of the solidified waste through a rate-limiting process by which immersion water penetrates into the solidified waste by diffusion. Presumably, the leaching can be evaluated using a diffusion model. Its diffusion coefficient can be evaluated as approximately
1 × 10－15m2/s, irrespective of the species of immersion water and chemical elements (except for low solubility substances).
