Thermomechanical interactions of particle bed-structural wall in a layered configuration. I: Effect of particle bed thermal expansions

Materials in the form of particle beds have been considered for shielding and tritium breeding and neutron multiplication in many of the conceptual reactor design studies. As the level of effort of the fusion blanket community in the area of out-of-pile and in-pile (ITER) testing of integrated test modules increases, so does the need for modelling capability for predicting the thermomechanical responses of the test modules under reactor environment. The thermomechanical responses of a particle bed-structural wall system in a layered configuration, subjected to bed temperature rise and/or external coolant pressure, were considered. Equations were derived which represent the dependence of the particle-to-particle and particle-to-wall contact forces and areas on the structural wall deformations and in turn on the thermomechanical loads. Using the derived equations, parametric analyses were performed to study the variations in the thermomechanical response quantities of a beryllium particle bed-stainless steel structural wall when subjected to thermomechanical loads. The results are presented in two parts. In part I, the derivation of the analytical equations and the effects of bed temperature rise are discussed. In part II, also presented in this symposium, the effects of external coolant pressure and the combined effects of bed temperature rise and coolant pressure on the thermomechanical responses are given. It is shown that, depending on the stiffness of the structural walls, uniform bed temperature rises in the range 100-400 deg C result in non-uniform effective thermal properties through the particle bed and could increase the bed effective thermal conductivity by a factor of 2-5 and the bed-wall interface thermal conductance by even a larger factor.