| In recent years,our country is committed to the development of nuclear energy.But the nuclear power plant in the course of the operation will inevitably produce a series of high radioactive nuclear waste,if disposed improperly,it will cause environmental pollution,and even threaten the health of citizens.In order to solve the the problem,China carry out clay rock high-level repository site selection work.Based on the comparison of the basic characteristics of the Nan Baxian,Long Dong,Tamusu and Su Hongtu candidate area,Tamusu and Su Hongtu in Inner Mongolia are considered as the most favorable candidate areas.The regional geological conditions in Tamusu candidate area have been studies in this paper,including the studies of data collection,geological investigation,clay rock thin section identification,Mapgis drawing and the seismic survey interpretation and so on.The studies mainly focused on the geological conditions in Tamusu candidate area such as hydrogeology conditions,natural geography,socio-economic and other conditions of the candidate area were also studied.Finally,a preliminary evaluation is made with reference to the safety criteria of clay rock type disposal repository.The results show that:(1)The regional tectonic environment of Tamusu candidate area is stable.Bayingobi basin is located in the transition part of Tianshan geosynclinal fold system and the North china platform,and divided into five relatively independent depression.The basin formation consists of the former Cretaceous strata(basins)and the Early Cretaceous to Quaternary strata(cap rocks).The fault structure in the basin is mainly distributed in the edge zone of each depression,controlling the sedimentary pattern of the basin.The magmatic rocks are mainly distributed in the basin base which was exposed to the surroundings of the basin.Due to the large thickness of the cap rocks in the depression,the magmatic rocks are only sporadic.(2)The clay rocks of Tamusu candidate area are in good geological conditions.The clay rock formation of upper part of lower Cretaceous Bayingobi is widely distributed and extending along the north-east direction.It's thickness is characterized by belts in S-N andblocks in E-W:The thickness gradually increased from north and south sides to the central and from west to east with the thickness of 0~320m and the embedded depth of more than400 m,extending a wide range and the occurrence is gentle.The fault development in the candidate area is commom,and the magmatic rock is rare.(3)The surface water system in the candidate area is not developed.A ccording to the regional lithology assemblage and its occurrence characteristics the groundwater is divided into bedrock fissure water,loose rock pore water and clastic rock fracture pore water.The bedrock fissure water is mainly distributed in the northern margin of the candidate area,receiving meteoric water'recharge and providing recharge for confined water.Loose rock pore water mainly occurs in the Quaternary eolian sand and loose gravel,receiving bedrock fissure water's recharge.Clastic rock fissures Pore water is the main groundwater in the area,receiving recharge from the first two types of water.It has a long flow paths.(4)The clay rocks(mudstone)in Tamusu candidate area are composed by the following mineral: kaolinite,illite,zeolite,dolomite,feldspar,pyrite and clastic minerals,etc.And the kaolinite,illite,zeolite with the strong adsorption characters can effectively slow down the migration of nuclides.(5)Tamusu candidate area has relatively flat terrain and terrain stability.It's also has a convenient transportation,which is conducive to high level radioactive transportation.It short for water system and vegetation,without hidden dangers of floods.The construction of the repository have little impact on the local socio-economy due to it's low population density and backward economy.(6)The preliminary evaluation results show that the regional geological conditions of Tamusu candidate area are ideal and all the conditions are in good agreement with the safety criteria. |
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