Conceptual Proposal: Reactor Cooled by High-Temperature Sodium Vapor

This paper presents a conceptual proposal that uses new ideas and novel combinations of old ideas to construct an inherently and passively safe compact and simple boiling sodium reactor. There is no pretense of detailed neutronic, structural, or thermal-hydraulic analyses. The fuel is particles of metal nitride ceramic or an alloy containing beryllium or niobium. Liquid sodium coolant enters at the bottom, flows around the fuel particles, and sodium vapor exits at the top, circulated by its boiling, not by pumps.The device consists of a reaction region connected to a storage region in which criticality is impossible. There are no control rods. The power output depends on the amount of fuel in the reaction region, which is controlled by gas pressure or electromagnetic pumps, and by circulation velocity and void fraction, which are controlled by gas injection. If the gas pressure or electromagnetic pump fails, fuel flows passively under the influence of gravity from the reaction region to the storage region and the reaction stops.The reaction region is small. The volume of circulating coolant is small. Therefore thermal inertia is small and power output can be changed rapidly. If electricity is produced by magnetohydrodynamic generators or thermoelectric diodes, the entire plant has essentially no moving parts other than the fuel, coolant, and pumps and valves that control gas pressures above the regions.External electrical power is not necessary for safety. Small volumes of sodium vapor and fuel slurry are removed continuously for processing, the latter even during shutdown, which reduces or eliminates the “iodine pit” startup control instability. There is no need to shut down the reactor for refueling. The capacity factor should well exceed 95%. Very high burnup is possible.