Impact of Advanced Fuel Cycles on Geological Disposal in a Clay Formation

The impact of six advanced fuel cycles, ranging from the present "once through" fuel cycle in light water reactors to a gas cooled fast reactor with fully recycling of all actinides, on geological disposal in a clay formation is evaluated. After a 50 years cooling time, the thermal output of the high-level radioactive waste arising from advanced fuel cycles is significantly lower than the one of spent fuel. This allows a reduction of the dimensions of the geological repository. The impact of advanced fuel cycles on the radiological consequences in the case of the expected evolution scenario is rather limited. The maximum dose, which is expected to occur a few tens of thousands of years after the disposal of the waste, is essentially due to fission products and their amount is about proportional to the heat generated by nuclear fission. The evolution of the radiotoxicity of the waste indicates that the radiological consequences of human intrusions into a repository will be significantly lower in case of waste arising from advanced fuel cycles.