Traces of ¹⁴c Emissions for the Operation Period of Two Ukrainian Npps: Rivne and Chornobyl

The aim of this study was a comparative retrospective assessment of radiocarbon ( 14 C) as a tracer, caused by operational emissions of Rivne and Chornobyl nuclear power plants (NPPs), which are equipped with different types of nuclear reactors. For this purpose, 14 C was studied in annual tree rings of pine taken at a distance of 1.5 km southwest of the Rivne NPP and at a distance of 3.5 km west-northwest of the Chornobyl NPP, near the Yaniv railway station. As a background, we use the 14 C in air data (Hua et al. 2013), which we continue for time interval 2009–2020 with our experimental data for pine tree rings. Tree rings were also collected in a rural area 60 km west of Kyiv, where industrial impact, in our opinion, is absent. 14 C in wood samples was determined using the conventional method based on liquid scintillation counting. It was found that the 14 C excess in the annual tree-ring samples of pine near the Chornobyl NPP during the observed operation period (1984–2000) was 3.0–13.0 pMC, except for the 1986, the year of the Chornobyl accident, when the 14 C value rose sharply to 182.7 pMC ( 14 C excess 62 pMC). After 2000, the content of 14 C in the air near the Chornobyl nuclear power plant did not exceed the background values within the uncertainty of the measured data. The concentration of 14 C in the samples of annual tree rings of pine near the Rivne NPP for the observation period (1986–2019) corresponded to the background levels within the uncertainty of the measured data. The study of environmental traces of 14 C emissions from two NPPs equipped with different types of reactors showed significantly lower emissions of Rivne NPP with VVER compared with emissions from Chornobyl NPP with RBMK reactors.