Solubility of airborne radioactive fuel particles from the Chernobyl reactor and implication to dose.

Airborne particles of nuclear fuel from the Chernobyl reactor that had been collected on air filters and stored, were characterised using in vitro dissolution tests to assess effective doses after their inhalation. As solvent, the Gamble biological fluid was used to simulate lung fluid. The solubility of the measured radionuclides decreased in the order (137)Cs>(90)Sr>>(241)Am>or=(239+240)Pu in the simulated lung fluid. The dissolution rate constant of e.g. (239+249)Pu ranged from 0.72 to 5.4 x 10(-6) g x cm(-2) d(-1) and decreased (for all nuclides) with increasing particle size as predicted from theoretical considerations. Considering the inhalation dose, decreasing dose with size and increasing doses with lower solubility may partly counterbalance each other for (137)Cs and (90)Sr. On the other hand, for (239)Pu and (241)Am larger particles and associated lower solubility both change the resulting dose in the same direction towards lower values. The comparison of the experimentally determined dose coefficients with ICRP values indicates that nuclear fuel particles closely resemble type M material characteristics for (137)Cs and (90)Sr and type S material characteristics for (239)Pu and (241)Am.