CH 4 and CO 2 emissions from geologic sources, which are devoid of radiocarbon ( 14 C), dilute the atmospheric 14 C/C ratio. Observations of 14 C/C can be used to estimate fossil fuel-derived CH 4 and CO 2 . However, the atmospheric 14 C/C ratio is perturbed by emissions of 14 C from nuclear power plants (NPPs) and fuel reprocessing sites, which may affect such 14 C/C-based estimation if they are not correctly quantified. We calculate NPP 14 C emissions for CO 2 and CH 4 from 1972-2016 using standard emission factors ( 14 C emitted per unit of power produced) and analyze trends in global and regional emissions. We use available observations of 14 C 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 14 C 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 14 C emissions.