Comparative absorption parameters of Pu and Am from PuO₂ and mixed oxide aerosols measured after in vitro dissolution test and inhalation in rats

Purpose: To compare specific absorption parameter values obtained from in vitro dissolution studies (this paper) and in vivo experiments (data published by Ramounet et al, 2000) and to determine their influence on Dose Per Unit Intake (DPUI) calculations. Materials and methods: Experiments were performed on plutonium oxide (PuO₂) and two Mixed Oxide (MOx) preparations containing 5% Pu (w/w) made according to the industrial process in vitro using a static test and in vivo after rat inhalation. Results: Behaviour of Pu and Am shows, in vitro, at shorter times, a greater rapid dissolution fraction f _r for Pu (factor 10) and Am (factor 2) with MOx powders compared with PuO₂, whereas in vivo results show a greater fraction f_r for Pu (factor 5) and Am (factor 15) with PuO₂ compared with MOx powders. This phenomenon has not been observed for slow dissolution absorption parameter s_s. The in vivo parameters for Pu and Am in these materials were very close to the default values recommended by International Commission for Radiological Protection for default Type S. Conclusions: Results obtained have shown that solubility of Pu from the mixed oxide was higher than that of Pu from PuO₂. Nevertheless, no significant difference was observed between the three compounds in the corresponding dose coefficients in vivo or in vitro. Therefore, for these particular compounds, variation in the chemical composition of the aerosols had no significant influence on DPUI. Consequently, in vitro, the dissolution test can provide a good estimate of the in vivo behaviour. Studies of variation of % Pu (w/w) from MOx are in progress in our laboratory to confirm these conclusions.