Activation and decay heat analysis of the European DEMO blanket concepts

Demonstrating tritium self-sufficiency is an important goal of the European tokamak demonstration fusion reactor. Currently four breeder blanket concepts are being considered: the Helium Cooled Pebble Bed (HCPB), Helium Cooled Lithium-Lead (HCLL), Dual Cooled Lithium-Lead (DCLL) and Water Cooled Lithium-Lead (WCLL). Differences in materials and construction of the four breeder blanket concepts lead to differing nuclear responses. As well as affecting tritium breeding this is also of particular importance in safety analyses, such as the modelling of loss of coolant accidents, as it affects the blanket's decay heat and nuclide inventory. This paper presents and discusses analysis performed for each of the 2014 designs of the blanket concepts to ascertain the decay heat and nuclide inventory for the entire reactor. It was found that the total decay heat at short decay times for the HCLL concept (17.5 MW at 1 s) was between 17% and 22% lower than the HCPB, WCLL and DCLL. At longer decay times (∼100 years) it was found that the DCLL and WCLL blankets had decay heats in the region of 2–3 orders of magnitude above the HCPB and HCLL blankets. The differences noted between the blanket concepts are discussed in terms of neutron spectrum and material composition.