A new model validation database for evaluating AERMOD, NRPB R91 and ADMS using krypton-85 data from BNFL Sellafield
The radioisotope krypton-85 (85Kr) is emitted into the atmosphere from nuclear fuel reprocessing plant. Releases from the BNFL Sellafield complex have been used to evaluate the performance of regulatory atmospheric dispersion models. Field measurements of 85Kr, associated emissions and meteorological data and dispersion model predictions have been collated into a model validation database that also includes routines to automate the execution of the models. This database allows the evaluation of subsets of data; in this paper we have considered local dispersion, to receptors within 3 km of the site, and regional dispersion, to receptors at distances of 12 km and 52 km from the site. Configurations of ADMS and AERMOD that implemented buildings and terrain modules showed a performance advantage. However, a modified configuration of the simpler NRPB R91 model, showed comparable results to the more complex models when all models were configured using effective stack heights. For regional scale dispersion statistically significant differences were not found between the models.
Keywords: nuclear fuel reprocessing, Gaussian plume model, complex site, tracer dispersion, air pollution, atmospheric dispersion modelling, krypton-85, 85Kr, Sellafield, meteorological data, ADMS, AERMOD, air quality, NRPB R91