SITE INVESTIGATIONS FOR A DEEP REPOSITORY FOR SPENT NUCLEAR FUEL AT FORSMARK - SWEDEN

摘要

Site investigations for a repository for spent nuclear fuel are presently in progress at Forsmark and at Oskarshamn, Sweden. The sites are located on the east coast of Sweden in a bedrock composed of Precambrian crystalline rocks. The goal is to obtain a permit to build a repository at one of the sites. The site investigations, which started in 2002, follow the same procedure at both sites. Information will be provided on the general progress of the siting work in Sweden with focus on the results from the investigations at Forsmark. The candidate area at Forsmark is approximately 10 square kilometres in size and extends south-eastwards from the nuclear power plant. It consists of a relatively less deformed tectonic lens, composed mainly of metagranite, that trends NW-SE. The lens is surrounded by highly deformed and inhomogeneous bedrock. Surface investigations have included bedrock and Quaternary cover mapping and fracture surveys. The sub-sea conditions outside Forsmark have been investigated with a marine seismic survey. An airborne geophysical survey and both reflection and refraction seismic surveys have been or are being carried out. So far, three vertical and five inclined 1,000 m long cored boreholes and 22 percussion boreholes have been drilled. Rock stress measurements using the overcoring method have been made in an additional 500 m deep borehole and by hydraulic methods in four boreholes. The oriented drill cores have been mapped and various analytical data have been assembled on core samples. Geophysical logging, hydrogeological tests and hydrogeochemical analyses have been carried out in all the boreholes. Rigorous measures are taken to ensure data quality.