Research On TRISO Particle's Structure And Failure Behavior

Solid fuel molten salt reactor uses spherical fuel element as fuel. The spherical fuel element contains fuel and non-fuel regions, in which the fuel region is formed by TRISO coated fuel particles uniformly dispersed in the graphite matrix. The TRISO coated particle consists of fuel kernel and four coated layers. In order to study the damage mechanisms of the TRISO particles, many countries have established TRISO particle analysis models which provide guidance to optimize the structure, to improve the performance and the manufacturing processes of the TRISO particles.The present work modified the German model of PANAMA by considering both the gas pressure and the creep and shrinkage effects of pyrolytic carbon layers on SiC layer. A calculation code is compiled and validated. By using the code, we are able to analyze the influence of the temperature distribution inside the spherical fuel element, the radius of kernel, the thicknesses of the coated layers and their distributions on the TRISO particles failure probability. The results show that it is necessary to consider the internal temperature distribution when calculating TRISO particles' average failure probability. At the same power density, the reduction in radius of fuel elements can reduce the temperature and its gradient and therefore the failure probability. The influence of the kernel radius and coating layer thickness and their distribution on the TRISO particles failure probability is evaluated. It is found that reducing the standard deviation of the buffer layer thickness distribution to 16?m can greatly improve the particle failure probability. The research achievements have great guidance on designing of the advanced coated fuel and coated fuel particles, and show ways to improve the manufacturing procedures of the coated fuel particles.