Temporal reduction of the external gamma dose rate due to 137Cs mobility in sandy beaches

Abstract

In the present paper the contribution to the external gamma dose rate due to 137 Cs in soil as a function of time is presented. Sampling sites were selected along the Calabria and Basilicata Regions coastal beaches (southern part of Italy) to assess the external gamma dose rate in air, 1 m above the ground level. A convection-dispersion model, with constant parameters was used to approximate the radiocesium soil vertical migration. The model was calibrated using the initial 137 Cs activity deposition in this region (Chernobyl fallout) and 137 Cs activity concentration down the soil profile, measured 10 years later. The dispersion coefficient and the advection velocity values, were respectively: 2.17 cm 2 y -1 and 0.32 cm y -1 . The Radionuclide Software Package (RSP), which uses a Monte Carlo simulation code, was used to determine the primary 137 Cs gamma dose contribution in air 1 m above the ground surface. The resulting 137 Cs external dose rate ranged from 0.42 nGy h -1 in 1986, to 0.05 nGy h -1 in 2007.

Natural radioactivity distribution and gammaradiation exposure of beach sands close to Kavalapluton, Greece

“…The absorbed gamma dose rate received implying a uniform distribution of radionuclides, was estimated using the following equation considering the necessary conversion factors (in nGy h −1 by Bq kg −1 ) to transform the activity concentrations of 40 K, 238 U and 232 Th(C K , C U and C Th respectively) in absorbed dose rate at 1m above the ground [5,17,[42][43][44][45][46].…”