REGIONAL ENGINEERING GEOLOGY SUITABILITY ASSESSMENT FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL OF PRE-SELECTED ALXA AREA

High level radioactive waste is the inevitable product of nuclear power development. The whole world has paid more attention to the safe disposal of the waste so as to maintain the sustainable development of nuclear power. Regional suitability assessment of engineering geology is one of the key tasks when siting the repository of high-radioactive waste disposal. Alxa area is one of the pre-selected areas for high level radioactive waste disposal in China. In order to identify pre-selected sites with good engineering geology in this area, the regional suitability assessment of engineering geology is necessary. Based on comprehensive index model and ArcGIS system, the regional engineering geology suitability of pre-selected Alxa region for high-level radioactive waste disposal is assessed. In comprehensive index model, the selection of assessment factors and determination of the weight value of factors are important. Due to the special purpose and requirements of high-radioactive waste site selection, the selection of assessment factors is different from that surface engineering. For example, the topography and rainfall factors are not in the consideration of high-radioactive waste site selection. According to field engineering geological survey and comprehensive data collection, lithology, faults, seismic, tectonic stress and tectonic terrain are selected as assessment factors. Considering the characteristics of multi-objective and fuzziness in suitability evaluation of high-radioactive waste disposal, analytic hierarchy process is used to determine the weight of each factor. On the basis of these factors, the comprehensive index is obtained. Then engineering geology suitability of Alxa region is classified into five levels according to the comprehensive index. They are respectively the better suitability, the good suitability, the moderate suitability, the poor suitability and the worse suitability. Evaluation results can provide reference for siting the repository of high-radioactive waste disposal. It is considered that the better suitability area and good suitability area in the assessment map can be considered as the site area. Among these area, Tamusu and Nuorigong are two sections with the level of the better to good suitability. Further site selection work can carried out in these two sections.