Аннотация:New data on microstructure of 16 years old (La, Pu)PO4 monazite ceramics doped with
8.1 wt% of 238Pu are presented. It is shown that the sample consists from at least two phases
differing in La/Pu ratio and small precipitates of Pu-phosphate. Possible mechanisms of the
compositional heterogeneity are discussed. Formation of Pu-containing rhabdophane after
sample storage in air is observed. This phenomenon together with gradual mechanical
destruction of the ceramic pellet formation of submicron particles will likely increase rate of
radionuclides loss from the monazite-based waste form. X-ray emission lines produced by
recoil uranium ions from Pu decay are analysed. It is suggested that careful examination of
their relative intensities may provide important information about behaviour of "hot" recoils
in nuclear waste forms.