3. Irradiation behavior of particle fuel

3.1 Mechanical and thermal behavior

The main containment barrier for TRISO fissile particles is the SiC layer, which is both an effective fission product diffusion barrier and, thanks to its high rigidity compared to pyrocarbon (ratio of one to ten), the structure that withstands the pressure generated by the fission gases released by the core into the open porosity of the buffer.

In addition to their usefulness during the manufacturing process and their role as an additional barrier to the diffusion of fission products, dense pyrocarbon layers play a major role in the mechanical strength of the SiC layer. Indeed, pyrocarbon layers, which are dense relative to the buffer but nevertheless contain 15-20% porosity, become denser under irradiation (effect of fast...