A Comparison of the Deuterium-Tritium Neutron Wall Load Distributions in Several Tokamak Fusion Reactor Designs

Since the tokamak scheme of plasma confinement provides a toroidal source of fusion neutrons,wide variations in the source distribution at the wall surface are possible. A numerical solution of the neutron streaming equation has been applied to the calculation of the flux and current as functions of wall position for a circular crosssection tokamak and two noncircular tokamaks, the Princeton Reference Design (PRD) and the University of Wisconsin UWMAK-I. The results show significant variations in the pattern of the angular flux and substantial peaking in the scalar flux and current. For example, the current peaks at 22% above nominal for the circular case, 43% for the PRD, and 12% for UWMAK-I. The nominal value, total source ÷ total area, is the commonly stated “wall load.” Effects of this magnitude cannot be ignored in future reactor designs when power densities, damage rates, etc., are evaluated.