Neutronics Design of Fusion Systems

Abstract

A fusion system is a facility that could utilize the energy released via a fusion reaction in a controllable and peaceful way. There are many facilities based on different methods to achieve the fusion reaction, including magnetic confinement fusion (MCF), inertial confinement fusion (ICF), etc. Among these facilities, the tokamak is the well-developed candidate for a commercial fusion system. In this chapter, the tokamak is used as a representative system to introduce the neutronics design of a fusion system. In a fusion system, the neutron carries most of the fusion energy (the kinetic energy of the neutron accounts for ~80% of the energy released by the D-T fusion reaction), is the key to attain the tritium self-sufficiency, and is also the source of radioactivity in the system. Thus, the neutronics design is a crucial step in fusion system design and is concerned with the feasibility, safety, economy, and environmental friendliness of the system. The neutronics design for the fusion system is focused on the blanket, tokamak machine, and corresponding buildings, related to the whole lifecycle of systems, including the procedures of design, licensing, operation, and decommission. Compared to fission energy systems, fusion systems have a more complex geometry and a harsher service environment for in-vessel components, which creates great challenges for neutronics design and analysis. In this chapter, our discussion on fusion systems will be as follows: (1) the principles, features, and typical conceptual designs of fusion systems; (2) the neutronics design principles, requirements, and methods; and (3) taking the Dual-cooled Lead Lithium (DLL) blanket adopted in FDS-II and the tokamak machine and buildings in the ITER as examples to illustrate neutronics design for the blanket, the tokamak machine, and the corresponding buildings, respectively.