Need for inboard shield to protect the center post of ST power plants

The center post (CP) is the most critical in-vessel component in spherical tokamaks (ST). Advanced ST power plant designs normally call for high neutr on wall loads (>5 MW/m(2)) forcing the CP to operate in a high radiation en vironment. Radiation degrades the physical properties of the current carryi ng conductor and severely affects the overall performance of the CP. An uns hielded CP does not appear to offer an attractive design. This paper presen ts the rationale for shielding the CP of ARIES-ST, the reasons for the desi gn choices, and the consequences of the choices on the power plant design.