TRISO fuel particles in high temperature reactors experience stress due to fission product build up inside the partice, shrinkage/swelling of the Pyrocarbon layers and thermal expansion. In most analyses of stress and strain, the mechanical model consists of a single particle in vacuum. However, in the fuel zone of present day pebble designs, the TRISO particles can be positioned within a relatively short distance from each other and it is therefore likely that the stress field of a given particle influences the stress state of its neighbors. Furthermore, the material in which the particles are embedded expericenes dimensional changes under irradiation, which in turn causes additional stress effects on the fuel particles.

In this paper, an attempt is made to expand existing visco-elasctic models to incorporate the above mentioned effects. It is found that the presence of the matrix material plays a significant role in the determination of the stresses that apply to a single isolated TRISO particle as well as in the transmission of the stresses between particles in actual pebble designs.

For more information, please contact j.l.kloosterman@tudelft.nl.