The Fluoride-Salt-Cooled High-Temperature Reactor (FHR) is a new reactor concept that uses the graphite-matrix coated-particle fuel from gas-cooled reactors and a high-temperature liquid salt coolant. The reactor exit temperatures exceed 700°C with reactor inlet temperatures of ∼600°C. Because of these high temperatures the FHR can be coupled to a nuclear air-Brayton combined-cycle (NACC) plant with one or more air-Brayton turbines with hot exhaust directed to a steam recovery boiler.

Under normal base-load operating conditions, air is compressed, heated using salt-air heat exchangers, passed through a turbine, and exhausted to a heat recovery boiler, and added electricity is made from the steam that is generated. The NACC can have one or more salt-to-air reheat stages. After air compression and nuclear heating, the hot compressed air is above the auto-ignition temperature of natural gas (NG). Natural gas can be injected to increase gas temperatures and produce peak power. Because the plant operates continuously as a base-load system connected to the grid and there is no need to control the fuel-to-air ratio, the peak power can be varied and increased rapidly. At times of low electricity prices, steam from the heat recovery boiler can be sold to industrial users at lower prices than they can generate it from NG but above its value for electricity generation. The incremental capital cost for peaking capabilities is less than the cost of stand-alone NG plants. There is the potential for the NG-to-electricity efficiencies exceeding those of stand-alone NG plants. These capabilities imply plant revenue 20 to 50% greater than from an equivalent base-load nuclear plant.

The market requirements are being assessed to determine the requirements for the FHR and NACC power cycle. As a new-type of plant, much additional work is required to understand the design options and limitations.

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