Performance Evaluation of Modern HTR TRISO Fuels

This report is a compilation of experience and results with TRISO-coated particles in spherical fuel elements. Its emphasis is on the application of these fuels in modular pebble-bed High Temperature Reactors (HTRs) with coolant exit temperatures up to 1000°C. Chapter 0 is a short assessment of attainable burn-up with modern HTR fuel particles. Chapter 1 is an introduction to the modular HTR and its fuel. This chapter also spells out fuel specifications and fuel requirements specifically tailored to the 200 MW_th steam-generating MODUL and the 170 MW_th process-heat MODUL. Chapter 2 describes fuel manufacture and quality assurance. Chapter 3 goes into details of the extensive German irradiation testing programs during the last decade with modern, high-quality, TRISO-coated particle fuels. Chapter 4 deals with heating test for accident simulation. Chapter 5 covers the current status of fuel performance modeling and fission product release predictions methods up to the fuel element surface. Chapter 6 covers a wide range of aspects pertaining to the graphite matrix used in spherical fuel elements. . Appendix A spells out the fission product source terms derived from free uranium in the fuel elements due to manufacture. Appendix B describes silicon carbide as the most important material in HTR fuel. Appendix C explains the PANAMA code for coated particle failure predictions.