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In 1954 the Oak Ridge Nationai Laboratory operated, for demonstration purposes, a high-temperature circulatingfuel reactor, employing as fuel enriched uranium fluoride dissolved in molten fluorides of other cations. A BeO moderator was used. At a maximum power of 2.5 Mw, 100 Mw hr were obtained. A negative temperature coefficient resulting largely from fuel expansion yielded exceptional stability of the reactor, and made the reactor a slave of the power demand. Xe/ sup 135/ and some of the other fission fragments are not retained in the fuel; hence, there is no xenon poisoning and relatively little danger of spreading of gaseous fission fragments in case of an accident. The advantages of liquid-fuel reactors (elimination of radiation dnmage and thermal stresses in solid fuel elements, ease of fabrication and fuel reprocessing) are combined with low pressures at very high temperatures. (auth)

Study carried out to determine a suitable reactor system or systems for the testing of water, gas, and liquid-metal cooled fuel assemblies.