Fig. 11-5 Particle-Bed Fuel Element for Helium-Cooled Burner Reactor Fuel for the proposed burner reactor consists of tiny particles of TRU nitride coated with layers of titanium nitride. Fuel particles are packed into the space between concentric porous tubes (frits) of a fuel element. The particles are directly cooled by helium gas flow through the particle bed. Since particle-bed type fuel has excellent thermal performance, it achieves a very high power density and a high transmutation rate.

A conceptual study has been performed on a dedicated reactor specifically designed for transmutation (burner reactor). Transmutation with this reactor results from fission reactions induced by neutrons in the reactor core. Transuranic elements, most of which are not fissile, undergo fission directly when neutrons much faster than those in a commercial fast reactor are used. The design study revealed the feasibility of the burner reactor core to utilize very fast neutrons. These neutrons would provide the performance to achieve a very high transmutation rate, about 300 kg/GWt/y, more than 20 times that of a power reactor. With the burner reactor, long-lived radioactive nuclides can be transmuted efficiently and effectively within a short period of time. Introduction of dedicated burner reactors also allows the partitioning and transmutation system to be separated from the existing nuclear power generation fuel cycle. This enables effective confinement of troublesome long-lived nuclides in the partitioning and transmutation system. The figure shows the concept of a particle-bed fuel element for a helium-cooled burner reactor. The fuel element contains a packed bed of tiny coated fuel particles that are directly cooled by helium gas flow. This type of fuel readily achieves the very high power density required for effective transmutation.

Reference T. Mukaiyama et al., Minor Actinide Transmutation in Fission Reactors and Fuel Cycle Considerations, Proc. Int. Information Exchange Meeting on Actinide and Fission Product Separation and Transmutation, ANL, (1992). 320.

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