Influence of preparation parameters on the synthesis of plastic scintillation microspheres and evaluation of sample preparation

Abstract

Plastic scintillation microspheres (PSm) are solid dispersions of fluorescent solutes encapsulated in a polymeric matrix; they are used to measure β and α decay of radionuclides. Since organic solvent evaporation/extraction methods have been successfully employed to produce PSm, this work evaluates the influence of different parameters (i.e., polystyrene (PS) and polyvinyl alcohol (PVA) concentrations, temperature, stirring speed and the organic/aqueous phase ratio) on the final size of the PSm; and the relationship between this final size and the radiometric capacities of the PSm in relation to emitters of both beta (3H, 14C and 90Sr/90Y) and alpha (241Am) radiation.The results show that when the concentration of PVA is increased, the size of the PSm decreases; meanwhile, an important decrease in particle size is also achieved when the PS concentration is decreased. For almost all the parameters evaluated, the resultant PSm were smoothed and spherical. However, when temperature was increased, the particle size increased and the PSm eventually became amorphous and porous. The observed decrease in particle size correlated with an increase in radiation detection efficiency and a movement in the positioning of the spectra at lower energy values.We also evaluated the reproducibility of the vial preparation for 3H measurements and confirmed that small variations in the quantity of PSm and preparation of different vials by different experimenters did not influence the radiometric capacities.