Radiological impact mitigation of waste coming from the European fusion reactor DEMO with DCLL breeding blanket

Abstract

In large fusion machines, as the foreseen DEMO, the high energy neutrons produced will cause the transmutation of the interacting materials which will become a source of radioactive waste. Besides the main constituents of a material that could transmute but which presence is essential, the impurities often give rise to significant additional activation compared to the base material. Thus, once identified the nuclides generating the dominant activation products for the DCLL (Dual Coolant Lithium-Lead) concept of Breeding Blanket (BB) for the European DEMO, the objective of the study has been to determine the impurity limits for such materials in order to minimize the radiological impact of the waste produced. This will enable to consider it as Low Level Waste and dispose it in the Spanish near-surface repository of El Cabril. For both the original compositions as well as the revised one with reduced amount of impurities, suggested to mitigate the waste impact, activation calculations have been performed. Hence, total beta-gamma activity, alfa activity, specific activity for different nuclides, decay heat and surface gamma dose rate have been analyzed with reference to the IAEA and SEAFP-2 standards for waste classification and to the specific regulations of El Cabril.