Distribution of carbon 14 in the terrestrial environment close to French nuclear power plants

For 10 years, 14C measurements have been performed around French nuclear power plant sites, both in zones influenced and zones not influenced by gaseous releases. Examining the results from these measurements in the terrestrial environment shows that the discharges have a very slight impact on the radiocarbon level (with a relative increase in the specific activity of the order of 3 Bq kg−1 C in the influenced areas). In correlation, there is a near-negligible increase in dose, on average less than 0.1 μSv yr−1, with reference to a dose from background radiation, which is of the order of 10 μSv yr−1. The values are very similar between the influenced zone and the non-influenced zone, with a mean of −27‰. The mean varies from 101‰ in the non-influenced zone to 123‰ in the influenced zone. Moreover, a general reduction in 14C concentration was found, with a time constant of the order of 95 years. The current level of 14C specific activity in terrestrial environment is estimated to be 242 ± 6 Bq kg−1 C.