Uncertainty and Sensitivity Analysis of an Upper Plenum Test Problem for the MAEROS Aerosol Model

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Abstract
The MAEROS aerosol model is being incorporated into the MELCOR code system for the calculation of risk from severe reactor accidents. To gain insight to assist in this incorporation, a computational test problem involving a three-component aerosol in the upper plenum of a pressurized water reactor was analyzed with MAEROS. The following topics were investigated: (1) the CRAY-1 CPU time requirements to implement and solve the system of differential equations on which MAEROS is based; (2) the effects on computational time and representational accuracy due to the use of different overall section boundaries and numbers of sections and components; and (3) the behavior of the aerosol and the variables that influence this behavior. Uncertainty and sensitivity analysis techniques based on Latin hypercube sampling and regression analysis were used in the investigation. Five sections and overall section boundaries from 0.1E-6 m to 50.E-6 m were found to be adequate for the problem under consideration. Further, solution time was found to be at least several hundred times faster than real time, which is felt to be adequate for MELCOR. Stepwise regression was used to investigate the sources of variation in computational time and suspended aerosol concentration.