Effect of engineering constraints on charged particle wall heat loads in DEMO

•A 2D model to evaluate the effect on the heat wall load of a large number of first wall profile and plasma shapes is presented.•A model to take into account some of the 3D feature and the misalignment tolerances of a 3D engineering wall is employed.•An automatic procedure to design a 2D first wall poloidal profile which fulfils heat flux density constraints on the wall is presented.•The calculation is verified with the 3D field line tracing code PFCflux, enhanced to satisfy the power balance. The presently predicted total heating power of the demonstration fusion reactor DEMO is ∼3 times the ITER value, while the major radius is only 1.5 times larger (R. Wenninger, et al., The DEMO Wall Load Challenge, Nucl. Fusion 57 (2017) 046002 (11pp)) [1]. The current DEMO technological wall heat load removal capability is limited to ∼1MW/m2, due to structural material limitations and the tritium breeding requirements, while the ITER first wall (FW) is designed for values up to 4.7MW/m2. This paper focuses on the evaluation of the effect of the engineering constraints on the required limitation of charged particle heat load. First, a 2D field-mapping tool is used together with a simple model to take into account the peaking factors present on an engineering 3D wall design. A sensitivity analysis is performed on a set of realistic FW 3D features considering a preliminary estimate of misalignments. The impact on the heat flux to the wall due to different machine geometries, plasma shapes variation, stationary plasma and plasma transients, is presented. An automatic procedure to define the 2D poloidal contour of the FW for minimized particle loads is presented. A subset of the resulting engineering wall design is analyzed using the 3D field line tracing code PFCflux.