GEOLOGICAL FORMATIONS IN BULGARIA SUITABLE FOR A DEEP HLW REPOSITORY

摘要

The total volume of vitrified high-level waste (HLW) and of intermediate-level wastes containing significant amounts of long-lived alpha emitters, generated over the lifetime of Kozloduy Nuclear Power Plant (NPP), is estimated to be about 2,100 m3. Selection of a suitable formation to host a deep HLW repository in Bulgaria presents serious difficulties owing to the small area of the country, its complex geology, and the expected negative reaction of the local population. After a preliminary categorization of the Bulgarian territory, more than 40 areas were identified initially as potential disposal sites. This number was reduced to 20 using a screening method. A large portion of the selected regions comprises thick (up to 1,000 m) Lower Cretaceous marls, some at a distance of 60-80 km to the south of Kozloduy NPP. There are no active faults in the vicinity of the chosen areas and the seismicity is of degree VII on the MSK scale. Several regions in south-east Bulgaria containing magmatic and metamorphic rocks, have been suggested as prospective sites for deep HLW disposal: the Byala Reka structure of Precambrian highly metamorphic gneisses, the Avren and Zalti Chal areas in meta-ultrabasites, the Sakar Palaeozoic granite pluton, and two areas in volcanogenic-sedimentary rocks. The possibility of subsea geological disposal has also been discussed. At present, a programme is being developed for more detailed investigations of the suitable geological formations.