A Comparison of Model Predictions of Gaseous Dispersion with Environmental Measurements of 14C Around Sellafield, UK

The Sellafield nuclear fuel reprocessing plant, sited 0.5 km from the coast, emits 14C to atmosphere primarily from two 120m high stacks. Measurements of 14C in hawthorn berries (Crataegus) at a distance of 4 km over six years shows significant variations in the net 14C per kg carbon with direction from the site. The predicted variation with direction, taking into account carbon uptake rate as well as the pattern of wind bearing and dispersion conditions through the growing season, shows reasonable agreement in most cases. The 14C distributions are largely accounted for by angular wind frequency during the daylight hours growing season, which for this site is markedly affected by sea breezes. For the years when there is a marked disagreement between the measured and predicted profiles the most likely explanation is considered to be curvature of the plume due to the influence of the hilly terrain.