Chernobyl fuel hot particles in man

A metabolic model for the behaviour of matrix-bound pulverized fuel particle radionuclides in the body is proposed. In fuel particles uranium oxides should be assigned to non transportable compounds of inhalation class Y with a half-time of slow clearance from the lung T1 ranging from 500 to 310-360 days. When fuel particles enter the gastrointestinal tract, the fractional absorption of matrix bound radionuclides does not exceed that of uranium oxides, i.e. 0.002. It is not until the uranium matrix is destroyed that fuel particle radionuclides enter the body fluids. This model suggests some new features of the human removal kinetics of Chernobyl radionuclides, as dependence on the particle size, dropping of T1 from 500-600 to 130 days, etc. The model has been verified using the results from: 1) intra vital monitoring of gamma-emitting fission products in victims who witnessed and managed the accident. A half time of 330 days for 137Cs corresponds to the Cs-137 behaviour in adults; only the value of 500 days for free model parameter Tl is consistent with the body counter data of the witnesses. 2) post-mortem studies of radionuclide distribution in organs. The R ratio (radionuclide content in the lung to that in the reminder of organs), as a criterion for assessment of metabolic properties, has been estimated for Pu. The expected median end mean AMAD (Activity Median Aerodynamic Diameter) estimates for fuel particles, determined by R(Pu), are 12 and 15 μm respectively. A suggestion for using the results in planning of protective measures and in assessment of health consequences of a major nuclear accidents has been made. (author)