Fast Reactor Design

Abstract

This chapter covers designs and analyses of the Super Fast Reactors. Fuel rod failure modes and associated fuel rod design criteria as well as a fuel rod design example are presented. The idea of locating hydrogenous moderator layers in the blanket assemblies for negative void reactivity is introduced. Three-dimensional nuclear core design procedure fully coupled with thermal-hydraulic calculation as well as several examples of core design is introduced. Evaluation method of the maximum cladding surface temperature by subchannel analysis and statistical thermal design procedure is introduced. The feedwater controller designed for the Super LWR is improved to be more suitable for the Super Fast Reactor where the main steam temperature changes more sensitively because of smaller heat capacity. Design of the power raising phase in the plant startup is presented in consideration of the thermal and thermal-hydraulic stability criteria. The influence of complicated two-pass flow scheme is emphasized. Safety of the Super Fast Reactor is found to be severer than that of the Super LWR due to the higher power density, smaller reactivity feedback, and the complicated two-pass flow scheme. Several design improvements of the core and safety system are proposed to improve the safety.