'DIRECT DISPOSAL'. Comparative study of the radiological risk of the spent fuel and vitrified waste disposals in granite deep geological formation

In order to study the implications of a possibly 'direct disposal' of the spent fuel a working group has been created in 1991. This report gives an evaluation of the radiological impact as well as of the technical and economical characteristics of a generic disposal scenario for untreated spent fuel. The basic scheme implies a temporary storage and, then after an adequate preparation, the disposal in a deep geological formation. This document concerning the evaluation of the radiological impact associated to the geological disposal of the spent fuel constitutes the IPSN's contribution to the report of working group. The solution, as defined by the group, specifies the disposal of multifunctional TSD containers ensuring the Transport, Storage and final Disposal in mine drifts of granite formation. Two values for amounts to be stored were taken into account: one corresponds to 43,500 fuel assemblies of PWR UOX type irradiated at 33,000 MWd.t-1, while the other, corresponds to 20,400 assemblies of the same type. The radiological risk was evaluated for two distinct evolution scenarios, one supposing the preservation of initial characteristics of the disposal site, the other supposing alterations like those induced by drilling deep water wells in the disposal's vicinity. The individual effective dose were computed for each of these scenarios. Also, a comparison is made between the case of direct disposal of spent fuels and the case of disposal of reprocessed fuels of the same type