Steady state and transient temperature profiles in a multishell spherical system heated internally by reactor-grade plutonium

Steady state and transient temperature distributions are analysed for multishell spherical systems which are heated in their inner part by the alpha-particle heat power of reactor-grade plutonium. Different geometrical thickness of the spherical shells and temperature dependent thermal material properties are assumed. Boundary conditions at the surface of the multishell system are natural convection by air and thermal radiation or cooling by cryogenic liquids. In addition, cooling by internal thermally conducting structures in outer shells is investigated by applying an approximate heat conduction model. The steady state and transient temperature distributions allow defining limits for alpha-particle heat power at different outer boundary conditions for which e.g. the melting points or other temperature limits of different materials are exceeded.