Radiocarbon dioxide (<sup>14</sup>CO<sub>2</sub>, reported in Δ<sup>14</sup>CO<sub>2</sub>) can be used to determine the fossil fuel CO<sub>2</sub> addition to the atmosphere, since fossil fuel CO<sub>2</sub> no longer contains any <sup>14</sup>C. After the release of CO<sub>2</sub> at the source, atmospheric transport causes dilution of strong local signals into the background and detectable gradients of Δ<sup>14</sup>CO<sub>2</sub> only remain in areas with high fossil fuel emissions. This fossil fuel signal can moreover be partially masked by the enriching effect that anthropogenic emissions of <sup>14</sup>CO<sub>2</sub> from the nuclear industry have on the atmospheric Δ<sup>14</sup>CO<sub>2</sub> signature. In this paper, we investigate the regional gradients in <sup>14</sup>CO<sub>2</sub> over the European continent and quantify the effect of the emissions from nuclear industry. We simulate the emissions and transport of fossil fuel CO<sub>2</sub> and nuclear <sup>14</sup>CO<sub>2</sub> for Western Europe using the Weather Research and Forecast model (WRF-Chem) for a period covering 6 summer months in 2008. We evaluate the expected CO<sub>2</sub> gradients and the resulting Δ<sup>14</sup>CO<sub>2</sub> in simulated integrated air samples over this period, as well as in simulated plant samples. <br><br> We find that the average gradients of fossil fuel CO<sub>2</sub> in the lower 1200 m of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution. The nuclear influence on Δ<sup>14</sup>CO<sub>2</sub> signatures varies considerably over the domain and for large areas in France and the UK it can range from 20 to more than 500% of the influence of fossil fuel emissions. Our simulations suggest that the resulting gradients in Δ<sup>14</sup>CO<sub>2</sub> are well captured in plant samples, but due to their time-varying uptake of CO<sub>2</sub>, their signature can be different with over 3‰ from the atmospheric samples in some regions. We conclude that the framework presented will be well-suited for the interpretation of actual air and plant <sup>14</sup>CO<sub>2</sub> samples.