Retrospective assessment of the radiological impact of 14 C discharges from a low‑power nuclear power plant

The paper presents the results of 14 C measurements in tree rings collected near the now‑decommissioned Bilibino Nuclear Power Plant (NPP), which operated four EGP-6 graphite-water reactors with a total electric capacity of 48 MW from 1974 to 2022. The sampling site was chosen based on long‑term meteorological data to represent the area with the highest potential 14 C level in the surface atmosphere resulting from Bilibino NPP discharges. The 14 C measurements were performed using accelerator mass spectrometry at the Budker Institute of Nuclear Physics in Novosibirsk, Russia. The results obtained range from 103.5 to 139.7 pMC, allowing the reconstruction of 14 C uptake into vegetation over the period 1974–2022. The largest anthropogenic contribution to the 14 C content was 6.0 pMC in 2020, which is likely due to maintenance work on the reactor’s graphite moderator. These results enabled the annual effective doses to the population from radiocarbon releases at the Bilibino NPP to be estimated. The maximum annual effective dose, about 3 µSv, was observed in 2020, which is far below the public dose limit of 1 mSv per year.