Patent Number: 
Section: claims

1. A method for preparing a powder of a solid solution of dioxide of uranium and of at least one other actinide and/or lanthanide element comprising:combusting a solution comprising uranyl nitrate and at least one nitrate of the other actinide and/or lanthanide element and glycine, the glycine being used in a predetermined amount in order to form, at the end of combusting, said solid solution, said predetermined amount being an over-stoichiometric amount of glycine relative to the uranyl nitrate obtained by:a) determining a combustion equation of uranyl nitrate, to which a factor φU is assigned to the stoichiometric coefficient of glycine;b) determining an over-stoichiometric amount of glycine, QU, by multiplying the amount of uranyl nitrate by the stoichiometric coefficient of glycine and by the factor φU, the latter being set to a value greater than 1;c) determining a combustion equation of the nitrate of the other actinide and/or lanthanide element, to which a factor φAn/Ln is assigned to the stoichiometric coefficient of glycine;d) determining an amount of the glycine, QAn/Ln, by multiplying the amount of the at least one nitrate of the other actinide and/or lanthanide element by the stoichiometric coefficient of the glycine and by the factor φAn/Ln, the latter being set to a value below 2; ande) obtaining said predetermined amount by adding at least the amounts of glycine determined in b) (QU) and d) (QAn/Ln), respectively. 2. The method for preparing a powder according to claim 1, wherein the factor φU has a value ranging from 1.5 to 1.7. 3. The method for preparing the powder according to claim 1, wherein the at least one nitrate of the other actinide and/or lanthanide element comprises:(i) for the nitrate of the other actinide element, a plutonium nitrate, a minor actinide nitrate and/or a thorium (IV) nitrate; and(ii) for the nitrate of the other lanthanide element, a lanthanide (III) or (IV) nitrate. 4. The method for preparing a powder according to claim 1, wherein the combusting comprises gradually heating the solution up to an ignition temperature. 5. The method for preparing a powder according to claim 1, further comprising, before the combusting, preparing the solution comprising uranyl nitrate and at least one nitrate of the other actinide and/or lanthanide element and glycine. 6. The method for preparing a powder according to claim 5, wherein preparing the solution comprising uranyl nitrate and at least one nitrate of the other actinide and/or lanthanide element and glycine consists of adding, to a first solution only comprising uranyl nitrate and at least one nitrate of the other actinide and/or lanthanide element, the predetermined amount of glycine.