The separation of U and U in the reprocessing of HTGR fuels is a key feature of the feed-breed fuel cycle concept. This is attained in the Fort St. Vrain (FSV) reactor by coating the fissile (Th-235u) particles and the fertile (Th-233U) particles separately with silicon carbide (SiC) layers to contain the fission products and to protect the kernels from burning in the head-end reprocessing steps. Pneumatic (gas) classification based on size and density differences is the reference process for separating the SiC-coated particles into fissile and fertile streams for subsequent handling.nTerminal velocities have been calculated for the + 2a ranges of particle sizes and densities for "Fissile B"—"Fertile A" particles used in the FSV reactor. Because of overlapping particle fractions, a continuous pneumatic separator appears infeasible;however, a batch separation process can be envisioned. Changing the gas from air to CO2 and/or the temperature to 300°C results in less than 10% change in calculated terminal velocities.
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