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Technical Standards, ALOHA-Comparison of ALOHA and EPIcode - November 13, 2006

November 13, 2006

Thoman, D. C.; O'Kula, K. R.; Laul, J. C.; Davis, M. W.; and Knecht, K. D.; Comparison of ALOHA and EPIcode for Safety Analysis Applications, Journal of Chemical Health & Safety, Volume 13, Number 6

EPIcode (version 7.0) and ALOHA (version 5.2.3) are two of the designated toolbox codes identified in the Department of Energy’s Implementation Plan for DNFSB Recommendation 2002-1 on Software Quality Assurance issues in the DOE Complex. Both have the capability to estimate evaporation rates from pools formed from chemical spills and to predict subsequent atmospheric transport and dispersion. This report provides an overview of the algorithms used by EPIcode and ALOHA to calculate evaporation rates and downwindplumeconcentrations.The technicalbases for thesealgorithmsare brieflydiscussed,anddifferences in the EPIcode and ALOHA methodologies highlighted. In addition, sample calculations are performed using EPIcode and ALOHA for selected chemicals under various environmental conditions. Side-by-side comparisons of results from sample calculations are analyzed to illustrate the impact that the different methodologies used by EPIcode and ALOHA have on predicted evaporation rates and downwind concentrations.