Wash-Off Effects in Urban Areas

The reduction of the activity distributed in urban areas in three Austrian cities after a radioactive fall-out, by run-off and wash-off effects from stabilised surfaces and the resulting dose reduction to the population were investigated four years after the Chernobyl fall-out to predict the long-term external exposure of the population. The measurements were performed in cities with different fractions of dry and wet deposition after the Chernobyl accident in order to determine whether any differences in radionuclide removal with regard to wet and ry fall-out was observable. High resolution in situ gamma spectroscopy was employed to measure the gamma flux from 137 Cs and 134 Cs at point over stabilised surfaces, which was then compared with undisturbed grass surfaces