Imaging underground electric structure over a potential HLRW disposal site

With fast development of Chinese economy, a large amount of garbage have been produced. Especially, high level radioactive waste (HLRW) bring dangers to the security of human being. Finding a suitable site to dispose HLRW is a key management to government. A potential HLRW disposal site has been chosen in west north of China at first, however, it is necessary to understand whether there exist electrical structures inside the rock mass, whether the rock mass is intact or not. We applied the controlled source audio-frequency magnetotelluric method (CSAMT) to confirm that. Three-dimensional numerical modeling of finite difference method was performed for typical structure in the study area, and response characteristics were analyzed to confirm which actual frequency range can be chosen and what structure dimension can be detected. Then we laid out 14 parallel survey lines to carry out data acquisition. By analyzing typical sounding curves, combined with drilling information and the inversion results, we suggest that the rock is intact and suitable for building a repository, which is a good recommendation for government department.