Thermal Stress Analyses of the Multilayered Fuel Particles of a Particle-Bed Reactor

Abstract

Particle-bed reactors have been proposed to provide high-temperature, low-mass power sources for space-based operation. A computer program was prepared to simulate the thermal and mechanical response of a multilayered fuel particle operating in such a reactor. Issues of concern include temperature gradient and interference thermal stresses, along with the plastic and creep deformations associated with the high temperature of operation. The results of the computer simulations indicate that the interference thermal stress is much larger than the temperature gradient stress and the external pressure stress, and that permanent strain formation cannot be avoided for particles operating at temperatures greater than ∼2300 K. The results also reveal some interesting aspects unique to multilayered fuel particle performance. Two such aspects include (a) the interaction between interference thermal stress and high-temperature creep and (b) the effect of power ramp time on the formation of time-dependent plastic strains.