Radionuclide entrainment coefficients by wash-off derived from plot experiments near Chernobyl

Abstract

This work aimed at treating the new database on cesium-137 and strontium-90 transfer by wash-off collected by IRSN in the framework of the Franco-German Initiative for Chernobyl. It focused on the 71 runoff plot (from 1 to 400 m²) experiments conducted under artificial rainfalls in the Chernobyl district between 1986 and 1998. These data, mostly still unpublished, provide a quantification of wash-off at the rainfall scale, still rare for radionuclides. Normalized entrainment coefficients by liquid and solid wash-off were calculated for each experiment. In average, the liquid entrainment coefficient was 10^-5 mm^-1 for cesium, and 10^-3.8 mm^-1 for strontium. The solid entrainment coefficient was 10^-41 m²g^-1 for cesium and 10^-4.3 m²g^-1 for strontium. These trends and values were found consistent with reported values in the literature. For assessment purposes, the extrapolation of these coefficients to wider areas and to other sites would need their physical interpretation.