Radionuclide transfer to wildlife at a ‘Reference site’ in the Chernobyl Exclusion Zone and resultant radiation exposures

TLDR

Stable element analyses are increasingly used to derive transfer parameters for radiological models, yet CEZ wildlife studies typically rely on ambient dose rates from handheld meters and assume low natural background levels. The study aims to fill a data gap in the ICRP framework by providing radionuclide transfer data for selected Reference Animals and Plants. In 2014, samples from a 0.4 km² site 5 km west of Chernobyl were analyzed for 137Cs, 90Sr, 241Am, Pu isotopes and stable elements to calculate organism‑soil concentration ratios and absorbed dose rates. The study, the first to sample a broad spectrum of species at a single CEZ site, found that stable element transfer for Cs and Sr is lower than that of the radionuclides, that ambient dose rates can underestimate organism dose by more than tenfold, and that natural background dose rates in the CEZ are comparable to many European regions.

Abstract

This study addresses a significant data deficiency in the developing environmental protection framework of the International Commission on Radiological Protection, namely a lack of radionuclide transfer data for some of the Reference Animals and Plants (RAPs). It is also the first study that has sampled such a wide range of species (invertebrates, plants, amphibians and small mammals) from a single terrestrial site in the Chernobyl Exclusion Zone (CEZ). Samples were collected in 2014 from the 0.4 km2 sampling site, located 5 km west of the Chernobyl Nuclear Power complex. We report radionuclide (137Cs, 90Sr, 241Am and Pu-isotopes) and stable element concentrations in wildlife and soil samples and use these to determine whole organism-soil concentration ratios and absorbed dose rates. Increasingly, stable element analyses are used to provide transfer parameters for radiological models. The study described here found that for both Cs and Sr the transfer of the stable element tended to be lower than that of the radionuclide; this is the first time that this has been demonstrated for Sr, though it is in agreement with limited evidence previously reported for Cs. Studies reporting radiation effects on wildlife in the CEZ generally relate observations to ambient dose rates determined using handheld dose meters. For the first time, we demonstrate that ambient dose rates may underestimate the actual dose rate for some organisms by more than an order of magnitude. When reporting effects studies from the CEZ, it has previously been suggested that the area has comparatively low natural background dose rates. However, on the basis of data reported here, dose rates to wildlife from natural background radionuclides within the CEZ are similar to those in many areas of Europe.