[en] The application of the Principal Components Analysis (PCA) methodology to the long-term assessment of operating releases from the nuclear power industry was investigated. Gaussian calculations had been previously compared with MATHEW/ADPIC calculations for a simulated 24-hr release in the Hudson River Valley and an area in the southeast. Considerable differences were noted in the comparisons, which were attributed to the more realistic simulation of the time and space varying wind fields by the MATHEW/ADPIC computer codes