Comparative activation analyses for the HCPB breeding blanket in DEMO

Abstract

The Helium Cooled Pebble Bed (HCPB) breeding blanket is one out of two concepts considered as driver blanket for the European DEMOnstration fusion power plant. The latest design, developed within the Breeding Blanket project of EUROfusion’s Power Plant Physics and Technology (PPPT) programme, assumes a fission-like breeder pin arrangement with breeder ceramics and Be12Ti as neutron multiplier.For the assessment of safety and waste management issues related to the use of the HCPB blanket in DEMO, a thorough activation analysis is required. Such an analysis should provide the total activity inventory and decay heat as well as the breakdown into components and materials as resulting from the irradiation over the assumed blanket lifetime in DEMO. An accurate calculation of the activity inventories requires the application of a suitable computational approach coupling the neutron transport simulation and the activation calculation with fully heterogeneous 3D geometry model of the DEMO.Precise materials specifications, including impurities and tramp materials, are essential prerequisites for adequate activation calculations. For the materials used in the HCPB blanket, the material compositions are provided with the material specifications set up for PPPT neutronics and activation calculations. These include the Eurofer steel, the breeder ceramics, tungsten and the beryllium in the Be12Ti used as neutron multiplier.Two difference tritium breeding material compositions of activation analyses were performed using each Li4SiO4+Li2TiO3 the latest material and previous material definition Li4SiO4. And beryllium titanate, the activation calculations were performed using the impurities specifications as provided by different potential beryllium suppliers. The most essential here is a uranium content in the ore used for the Be12Ti metallurgical engineering. This can permit a justification of the potential environmental risks associated with the application of the various materials options. The effect of the different Lithium compositions on the activity, both on the short- and long-term time scale, is evaluated in this work in the context of the radioactive waste management issue for DEMO.