[en] FLECK has been developed as a rapid fuel management calculation to produce time dependent mean zone cross-sections for input to radial reactor calculations. It uses channel averaged irradiation dependent data as input and averages over a histogram of channel irradiations for each zone. Refuelling may be carried out at specified rates or to meet specified reactivity criteria. The transfer of data at both input and output has been made flexible, and allows considerable automation of the calculational route in which it is used. (author)