Abstract: The invention relates to a process for the preparation of a product based on a phosphate of at least one element M(IV), for example of thorium and/or of actinide(IV)(s). This process comprises the following stages: a) mixing a solution of thorium(IV) and/or of at least one actinide(IV) with a phosphoric acid solution in amounts such that the molar ratio PO 4 M ? ? ( IV ) ?is from 1.4 to 2, b) heating the mixture of the solutions in a closed container at a temperature of 50 to 250° C. in order to precipitate a product comprising a phosphate of at least one element M chosen from thorium(IV) and actinide(IV)s having a P/M molar ratio of 1.5, and c) separating the precipitated product from the solution. The precipitate can be converted to phosphate/diphosphate of thorium and of actinide(s). The process also applies to the separation of uranyl ions from other cations.

Abstract: The invention relates to a process for the preparation of a product based on a phosphate of at least one element M(IV), for example of thorium and/or of actinide(IV)(s). This process comprises the following stages: a) mixing a solution of thorium(IV) and/or of at least one actinide(IV) with a phosphoric acid solution in amounts such that the molar ratio PO 4 M ? ? ? ( IV ) is from 1.4 to 2, b) heating the mixture of the solutions in a closed container at a temperature of 50 to 250° C. in order to precipitate a product comprising a phosphate of at least one element M chosen from thorium(IV) and actinide(IV)s having a P/M molar ratio of 1.5, and c) separating the precipitated product from the solution. The precipitate can be converted to phosphate/diphosphate of thorium and of actinide(s). The process also applies to the separation of uranyl ions from other cations.

Abstract: The invention relates to novel thorium phosphates, their preparation process and their use for the storage of radioactive products.These novel thorium phosphates comply with the formulas Th.sub.4 P.sub.6 O.sub.23 (I) or Th.sub.4-x M.sub.4x/v P.sub.6 O.sub.23 (III) in which:M is a monovalent, divalent, trivalent or tetravalent cation,v represents the valency state of the cation and is equal to 1, 2, 3 or 4, andx is such that:0<x.ltoreq.3 when v=40<x.ltoreq.0.26 when v=30<x.ltoreq.0.1 when v=2, and0<x.ltoreq.0.036 when v=1.The cation M can in particular be a radioactive element.

Abstract: Thorium tetrabromide has been found to exhibit fluorescence and radioluminescence with emission of blue light in the range from 3400 to 4800 A with a maximum around 4000 A in response to electromagnetic waves shorter than 3000 A, whether ultraviolet, X or gamma rays and also in response to energetic charged particle radiation, such as alpha rays, beta rays, protons and heavy ions. Because of the radioactive decay of thorium, there is a background autoluminescence. Crystals of thorium tetrabromide are transparent to its luminescence radiation and are particularly suitable for radiation detectors and measurements, frequency converter, standards, radioisotopic microgenerators of electricity, and the like. They are also useable as neutron flux detectors, for thermal and fast neutrons because the component elements of the crystal react with neutrons to respectively produce neutrons activation reactions and fission reactions.