EARLY DOSE ASSESSMENT IN CRITICALITY ACCIDENTS

TLDR

Early dose estimation is valuable for severe radiation accidents, and prior work showed lymphocyte depletion follows an exponential decline for gamma accidents with doses between 50 cGy and 8–10 Gy, with the depletion rate constant linearly related to dose. The authors aim to extend this simple technique to analyze various types of criticality accidents, including liquid processes, water‑moderated systems, and metallic systems. The method involves applying the same exponential lymphocyte depletion model to criticality accident scenarios, allowing dose estimation from blood counts. Results indicate that lymphocyte depletion in high‑level mixed gamma/neutron accidents matches that of gamma accidents at the same effective dose, suggesting a neutron RBE near unity, and the technique remains robust across different gamma and neutron spectra for initial dose estimation.

Abstract

Early estimation of dose is useful in the medical evaluation of severe radiation accidents. In a prior publication, lymphocyte depletion kinetics were shown to follow an exponential decline for gamma accidents in which the average whole-body dose was in the range 50 cGy < D < 8–10 Gy. In that study, the depletion rate constant was linearly related to dose, within the statistical variation of the historical hematological data. This simple technique has now been extended to include analysis of various types of criticality accidents (liquid process; water moderated systems; metallic systems). Lymphocyte depletion in high-level mixed gamma/neutron accidents is found to be approximately equal, at a given effective dose, to that for gamma accidents. This universality would indicate a neutron RBE for human lymphocytes close to unity. Furthermore, the technique appears to be insensitive to the shape of gamma and neutron spectra, therefore making it especially robust for initial, approximate dose estimation.