Optimisation of inert matrix fuel concepts for americium transmutation

Concepts of inert-matrix fuels for americium transmutation are discussed. I t is demonstrated that a 'hybrid' fuel design, consisting in a dispersion o f an americium-bearing phase in an inert matrix, is desirable. More than a solid-solution is preferred in order to localise within a small volume the damage in the matrix due to fission fragments. Such a dispersion is compose d of spherical inclusions (between 50 and 300 mu m) of an americium host ph ase in a dense inert matrix. For an oxide fuel, we recommend the solid solu tion (Zr,Am)O-2, possibly stabilised by yttrium as the host phase. For a ni tride fuel, (Zr,Am)N is proposed. MgO and MgAl2O4 (oxide fuel), as well as TiN and ZrN (nitride fuel) are the most likely candidates for the inert mat rix. Recommendations are also given for the research required to optimise t he concept. (C) 1999 Elsevier Science B.V. All rights reserved.