Development of a stress analysis code for TRISO particles in HTRs

The PUMA project is a Specific Targeted Research Project of the European Union EURATOM 6th Framework Program. Complementary with other initiatives, the PUMA project is mainly aimed at providing additional key elements for the utilisation and transmutation of plutonium and minor actinides in high temperature gas-cooled reactor designs. Within PUMA, new coated particle designs for Pu/MA incineration will be explored. For this purpose, Delft University of Technology (TU-Delft) participates in the optimisation of the fuel design of HTRs fuelled with plutonium and/or minor actinides by calculating the failure fraction of TRISO particles during irradiation in a given reactor core design. This is achieved by coupling a neutronics, thermal-hydraulics and fuel depletion code system, which delivers the fuel temperature, fast neutron flux and power density profiles, to an in-house developed stress analysis code. The latter is being further developed to provide a reliable and realistic failure fraction. Application to a PBMR-400 design fuelled with 1st generation Plutonium and with a target burn-up of 700 MWd/kgHM shows promising results in terms of Pu-burning capabilities. The TRISO particle failure fraction is also calculated and compared to U-based fuel particles. It is shown that the Pu-based fuel particles need a better design and this can be achieved by use of the present stress analysis code.