A high-gain fusion-fission reactor for producing uranium-233

The neutronics of several hybrid fission-fusion reactors were analyzed using a computational method based on the ANISN transport code (Engle, 1967) to develop a design capable of producing large quantities of U-233 while maintaining a tritium breeding ratio greater than unity. In the optimum design, an equilibrium concentration of Pu-239 and U-238 replaces thorium in a converter region, significantly increasing the multiplication of 14-MeV source neutrons. The tritium and fissile breeding rates of the reactor are 1.052 and 1.880, respectively, and 3.537 U-233 nuclei are produced per fusion neutron. The results of two series of time-dependent calculations, analyzing the long-term operation of a near optimal hybrid reactor for U-233 production and short-term operation to produce the 30,000 kg of Pu-239 required to initiate the long-term process, are presented.