Variation of solubility, biokinetics and dose coefficient of industrial uranium oxides according to the specific surface area

The in vitro solubility, absorption to blood, lung retention and dose coefficient of industrial UO2 samples were studied as a function of the specific surface area (SSA) of the particles. An in vitro study has been carried out on two samples of industrial UO4 to compare the results with those obtained with UO2. Ten UO2 samples supplied by different fuel factories or research laboratories, presented specific surface areas from 1.00 to 4.45 m2.g-1. The wide range of values of SSA was due to the different conditions of fabrication. Dissolution tests in cell culture medium made on these ten samples have shown that the solubility increased 2.5-fold when the SSA increased 1.7-fold. The same tendency has been found for UO4, a soluble compound, and for U3O8, a moderately soluble compound. Four in vivo experiments carried out on rats by intratracheal instillation of dust suspensions of UO2, have highlighted the decrease in lung retention and the increase of absorption to blood with the SSA. The experimental absorption parameters calculated from the in vivo data allowed specific dose coefficients to be obtained which decreased from 6.6 to 4.3 μSv.Bq-1 when the SSA increased from 1.60 to 3.08 m2.g-1. Thus, the medical monitoring of workers at the workplace has to take into account any change in the fabrication process of the uranium compound which can affect the physiochemical properties and consequently the dose coefficient. (author)