Preliminary fabrication and characterisation of inert matrix and thoria fuels for plutonium disposition in light water reactors

The plutonium disposition is presently acknowledged as a most urgent issue at the world level. Inert matrix and thoria fuel concepts for Pu burning in LWRs show good potential in providing effective and ultimate solutions to this issue. In non-fertile (U-free) inert matrix fuel, plutonium oxide is d iluted within inert oxides such as stabilised ZrO2, Al2O3, MgO or MgAl2O4. Thoria addition, which helps improve neutronic characteristics of inert fue ls, appears as a promising variant of U-free fuel. In the context of an R&D activity aimed at assessing the feasibility of the fuel concept above, sim ulated fuel pellets have been produced both from dry-powder metallurgy and the sol-gel route. Results show that they can be fabricated by matching bas ic nuclear grade specifications such as the required geometry, density and microstructure. Some characterisation testing dealing with thermo-physical properties, ion irradiation damage and solubility also have been started. R esults from thermo-physical measurements at room temperature have been achi eved. A main feature stemming from solubility testing outcomes is a very hi gh chemical stability which should render the fuel strongly diversion resis tant and suitable for direct final disposal in deep geological repository ( once-through solution). (C) 1999 Elsevier Science B.V. All rights reserved.