Safety and control of modular liquid-metal reactors

As part of recent development efforts on advanced reactor designs Argonne National Laboratory has proposed the integral fast reactor (IFR) concept. The IFR concept is currently being applied to modular-sized reactors, which would be built in multiple power packs together with an integrated fuel-cycle facility. It has been amply demonstrated that the concept, as applied to modular designs, has significant advantages in regard to anticipated transients without scram (ATWS). Attention is now focused on whether or not those advantages derived from the IFR traits can be translated to the operational/design-basis-accident class of transients. Inherent operability, in which reactor power control is effected through the use of primary pumps and balance-of-plant (BOP) swings rather than through the active motion of control rods, is a proposal to utilize the enhanced inherent feedback response of the IFR to improve the operating characteristics of liquid-metal reactors (LMRs). The scheme has associated with it potential advantages in the areas of plant control and design simplification. This study on inherent operability in modular LMRs therefore has implications for both operational and ATWS events. Current intentions are to analytically explore possibilities of applying various schemes to advanced LMRs with the aid of the SASSYS system code and then to test viable alternatives in the Experimental Breeder Reactor II (EBR-II) plant under the auspices of the inherent safety operability testing program