ON THE MINIMUM OVERALL SIZE OF A REFLECTED PEBBLE-BED REACTOR

The minimum overall size of a reflected pebble-bed reactor is, in general, considerably smaller than that of the corresponding bare-critical assembly. It becomes meaningful, therefore, to refer to reflector savings in terms of overall size and not just in terms of core dimensions or fuel requirements, as is usually the practice for other types of thermal reactors. This paper considers, for the purpose of illustration, numerical results for a spherical reactor fueled with low-enriched uranium (LEU) pebble-bed fuel elements at average burnup. The factors that contribute to the significant size-savings from the reflector are discussed, as are certain practical implications such as the possible dual criticality of a system of fixed outer dimensions.