Disposal of radioactive wastes in Italian clays: mined repository or deep boreholes

The projected development of nuclear power generating capacity in Italy will result in an eventual installed capacity of about 10GWe by the turn of the century. Current plans for management of the spent fuel from this program involve reprocessing and vitrification under contract with BNFL in the United Kingdom, storage of returned wastes, and disposal in a suitable clay formation on the Italian mainland or in Sicily. Although there is scope for disposal in other rock types (rock salt for example) the main thrust of present studies aims at using the Pliocene-Pleistocene 'blue clays' which are present in considerable thicknesses in various basinal structures throughout Italy. The scale of the problem is small, since only an estimated 2500 tonnes of vitrified waste will arise from the reference program which will have run to completion by about 2025. In addition, there will be a further 5200 tonnes of cladding hull materials (including the lead-alloy embedding matrix for packaging) which are being considered for co-disposal with the high-level wastes in the same facility. Two disposal methods are being assessed, either emplacement in a mined repository or sealing into deep boreholes drilled from the surface. This paper outlines the results of a preliminary feasibility study, which has compared engineering aspects, costs, practicality and long-term safety of these two options. (Auth.)