To analyze the aerosol dynamics in severe accidents of LMFBR, a new computer code has been developed. The code entitled MCAD (Multicomponent Aerosol Dynamics) can treat two component aerosol system in accident scenarios. Coagulation and removal mechanisms are included in this model. In order to see the effect of particle geometry, the code makes use of the concept of shape factors or density correction factor. In this code, they are utilized simultaneously and their effects are explained. To simplify the process of multicomponent interactions, geometric constraints are considered in calculation of coagulation coefficient. The code is verified using the experimental result of NSPP-300 series and compared to other code. At present, it fits the result of experiment very well and agrees to the existing code. But, it is very complicate and cumbersome to treat containment circumstance. Hence, several factors have to be studied for accurate analysis. The input variables included are very uncertain. Therefore uncertainty and sensitivity analysis is essential as a supplement to code development. In this analysis, Latin hypercube sampling and experimental design method are compared. 14 variables are selected to analyze the input uncertainty. The analytical result gives an insight to which variables are significant as time elapse and their reasonable ranges. Therefore, these procedures are repeated until a good fitting is achieved.