Gas Generation and Migration Analysis for TRU waste Disposal System

Ando, Kenichi*; Noda, Masaru*; Yamamoto, Mikihiko*; Mihara, Morihiro  

In TRU waste disposal system, significant quantities of gases may be generated due to metal corrosion, radiolysis effect and microorganism activities. It is therefore recommended that the potential impact of gas generation and migration on TRU waste repository should be evaluated. In this study, gas generation rates were calculated in the repository and gas migration analyses in the disposal system were carried out using two phase flow model with results of gas generation rates. First, the time dependencies of gas generation rate in each TRU waste repositories were evaluated based on amounts of metal, organic matter and radioactivity. Next, the accumulation pressure of gases and expelled pore water volume contained nuclides in the repository were calculated by TOUGH2 code. After that, the results showed that the increase of gas pressure was the range of 1.3 to 1.4MPa. In the repository with and without buffer, the rate of expelled pore water was 0.006 - 0. 009m/y and 0.018 - 0. 024m/y, respectively. In addition, the radioactive gas migration through the repository and geosphare are evaluated. And re-saturation analysis is also performed to evaluate the initial condition of the system.