Designing for Inherent Control in Liquid Metal Advanced SMRs - 14162

Simulation results are presented for a design strategy that seeks to achieve inherent control and passive safety for liquid metal advanced SMRs. The approach places an increased reliance on passive feedbacks to regulate plant operation. A reference liquid-metal reactor design is defined to serve as a baseline against which innovative design concepts can be compared with respect to operational performance. The definition assigns values to key plant parameters related to materials type, component data, system configuration (loop vs. pool type), fuel cycle (burner vs. break-even vs. breeder) and balance of plant. The reference design represents the state-of-the-art of conventional fast reactor technology in terms of economics of electricity production, use of active control systems and standard operation (e.g. refueling every two to three years). Innovative design features and associated control strategies are then investigated for reducing the size of upset imitators and for improving also the safety of the inherent response to the initiator. Initiators include failures of active systems and operator errors. At the same time the ability of the modified plant to meet normal grid demands subject to constraints on temperature rates of change is assessed. Results presented indicate that operational performance can be maintained while active system initiator size is reduced resulting in improved safety. Essentially the innovations introduce inherent feedback mechanisms that serve to reduce the magnitude of the control action of the active control systems. (authors)