SUMMARY

Although there is considerable interest and experience with Liquid Metal Cooled Fast Reactors, several aspects of the design and safety of these reactors have not been sufficiently studied and require further investigation, specifically the effect that the choice of fuel has on the safety characteristics of the reactor. The two most successful and promising fuel types in Fast Reactors are metallic and oxide, and a third, nitride, appears to be a feasible option. It has not been determined, however, whether any of these fuel types provide superior safety characteristics in LMFRs. The purpose of this study is to examine the impact of the fuel type on the inherent safety characteristics of a Liquid Metal Fast Reactor. General Electric's S-PRISM Sodium Cooled Fast Reactor was chosen as the baseline reactor for this study because it has a power level of 1,000 MWt, which is representative of an average fast reactor, and was designed for either a metallic or oxide core. A series of unprotected reactor accidents will be simulated for both the metallic and oxide cores using the thermal hydraulics code RELAP5-3D to provide a better understanding of the impact that the choice of fuel has on the safety properties of the reactor. In addition, several protected reactor accidents will be simulated to examine the effect that the fuel type has on reactor shut down and natural circulation in the core. After simulating the metallic and oxide core transients, the S-PRISM core will be redesigned for a nitride-fueled core. The previous simulations will then be repeated for the nitride core.