GLOBAL AND REGIONAL EMISSIONS OF RADIOCARBON FROM NUCLEAR POWER PLANTS FROM 1972 TO 2016

CH4 and CO2 emissions from geologic sources, which are devoid of radiocarbon (C-14), dilute the atmospheric C-14/C ratio. Observations of C-14/C can be used to estimate fossil fuel-derived CH4 and CO2. However, the atmospheric C-14/C ratio is perturbed by emissions of C-14 from nuclear power plants (NPPs) and fuel reprocessing sites, which may affect such C-14/C-based estimation if they are not correctly quantified. We calculate NPP C-14 emissions for CO2 and CH4 from 1972-2016 using standard emission factors (C-14 emitted per unit of power produced) and analyze trends in global and regional emissions. We use available observations of C-14 emissions and power generation in Europe to assess emission factors for different reactor types, as well as potential differences related to the age or manufacturer of the NPPs. Globally, nuclear C-14 emissions increase until 2005 and then decrease, mostly because of the closure of gas-cooled reactors in the United Kindom and the shutdown of light water reactors after the Fukushima nuclear accident in March 2011. Observed emission factors in Europe show strong variability, spanning values from 0.003 to 2.521 TBq/GWa for PWR and from 0.007 to 1.732 TBq/GWa for BWR reactors, suggesting more information and more sophisticated models are needed to improve estimates of C-14 emissions.