Comparison of MACCS, ARANO and VALMA

The purpose was to learn and understand the functionality of WinMACCS. Besides available documentation, it is necessary to exercise in practice the usage of the code. Comparison calculations were carried out by ARAÑO and VALMA. Calculations deal with offsite dose calculations without countermeasures in a single weather condition as well as with the probabilistic approach employing annual weather data.

The principal phenomena included in both codes are atmospheric transport and deposition under prevailing meteorology, short- and long-term mitigation actions and exposure pathways, deterministic and stochastic health effects, and economic costs. MACCS was developed as a general-purpose tool applicable to diverse reactor and nonrcactor facilities licensed by the US Nuclear Regulatory Commission.

Calculation results indicate significant differences in some single atmospheric dispersion cases but differences arc reduced if annual weather is used and fractilc values arc presented. Then ARAÑO typically predicts smaller dose values than MACCS. Implementation of MACCS demonstrates that the code is available and capable to calculate offsite radiation doses. In addition, long-range model VALMA was included in comparisons. Comparable dose estimates of VALMA predict smaller dose values than MACCS.

To study the differences possibly caused by different weather data sources (NPP weather mast, or SILAM dispersion model), some parameter distributions are included in the Appendix.