Neutronics related integration studies of EU-DEMO pellet injection system

Abstract

• The problem of the integration of the pellet injection line system from neutronic and thermal point of view is presented. • The evolution of the design of the pellet injection system from inboard side of the machine is presented. • A neutronic preliminary assessment of an alternative solution for pellet injection system from the upper port of the machine has been studied. • All analyses have been done using MCNP-5 Monte Carlo code and ADVANTG hybrid has been used to implement specific variance reduction techniques. In the frame of the EU DEMO development program within the EUROfusion Consortium, the integration of the in-vessel components is crucial even at an early stage of the design process. The auxiliary, heating and fueling systems have to be integrated into the Breeding Blanket and, thus, they will undergo to a harsh nuclear environment during operation, and have a significant impact on the Tritium Breeding capability, loads and shielding performances. This work presents the neutronics and thermal analyses performed to support the integration studies of the pellet injection systems. This study is mainly devoted to optimize the design of a fueling line option consisting in a protrusion of the Vacuum Vessel (VV) in the inboard side supporting a guiding tube to drive the pellets along the ideal trajectory as close as possible to the First Wall. An alternative concept with a free-flight injector through the upper port, has also been studied evaluating the feasibility and the shielding needs. The three-dimensional neutronics simulations were carried-out with the MCNP5 Monte-Carlo code using a DEMO model with the integrated systems to calculate neutron fluxes, damage and nuclear heating distribution. Thermal analyses were carried-out using ABAQUS. Results of neutronics and thermal analyses on the fueling systems are presented and discussed.