Natural apatitic phosphosilicates, generally called “britholites”, were found to contain certain amounts of radioactive elements or fission products. Thus, britholites have been the object of a great interest because of their potential application as typical matrices for the conditioning of nuclear wastes. In the present report, uranium-doped oxy-silicophosphates Ca x La y (SiO 4 ) 6−u (PO 4 ) u O t /U were synthesized by high-temperature solid-state reaction. The prepared compounds were characterized by X-ray diffraction method, Raman diffusion spectroscopy and X-ray microprobe. The uranium solubility in such compounds was studied. The uranium thermal diffusion in the britholite with the theoretical formula Ca 5 La 5 (SiO 4 ) 3 (PO 4 ) 3 O 2 was estimated. The bands present in the Raman spectra were identified and assigned to the corresponding vibration modes of SiO 4 and PO 4 anions. The diffusion coefficient of uranium in the studied apatite was found close to that calculated for europium and lanthanum in some other apatites.