This system is the second runner in both the United States and Europe, with possibly greater economic potential than the liquid-metal-cooled variety. However, it still has development problems to overcome (Fig. 2.2).

The particular version discussed here is a British design (2) which uses coated particle technology to produce a novel fuel that allows very high outlet temperatures in the range of 1000°C (1830°F). The fuel uses small silicon carbide coated particles of mixed carbide fuel which retain the deve­loped fission products. The power density is in the range of 240 W/cm3. The coolant is helium operating at a pressure of above 750 psia, and po­tentially the system has promise in direct cycle use with the addition of a gas turbine. Table 2.1 shows the main chacteristics for a 1000 MWe version of this reactor system.