Luminescence dosimetry in a contaminated settlement of the Techa River valley, Southern Urals, Russia

Optically stimulated luminescence (OSL) dosimetry is applied to quartz extracted from bricks from a mill in a contaminated village (Muslyumovo) of the Techa River valley, Southern Urals, Russia, for the purpose of dose reconstruction. Previous works [Göksu et al., 2002. First international intercomparison of luminescence techniques using samples from the Techa river valley. Health Phys. 82, 94–101] have shown that the expected dose due to man-made sources of radiation in the bricks is in the same range as the background dose due to natural sources of radiation, therefore a precise estimate of the cumulative and background dose is of utmost importance. Cumulative doses could be assessed with OSL with a precision of around 4% and lie between 450 and 600 mGy. The background dose was carefully determined by a combination of laboratory measurements, in-situ gamma spectrometry and Monte Carlo modelling. The results show that the gamma-dose rate of the soil was overestimated and the fractional brick gamma-dose rate underestimated in previous studies, but that the overall gamma-dose rate was nearly correct, due to mutual compensation. The obtained anthropogenic doses in brick measured with OSL lie between 200 and 300 mGy, show variability between adjacent bricks within error limits for one spot but a significant difference for two samples is observed for another spot. A distinct dependency of measured dose upon sample height is observed, which is an indication of a source distribution, which extends over a large area and up to a certain depth into the soil and in which higher contaminated areas are located at a greater distance to the mill than lower contaminated areas. A measured dose–depth profile is compared with previously published Monte Carlo calculations to verify the source energy.