HAARM, Time-Dependent Diffusion and Deposition of Radioactive Aerosols, LMFBR Accidents

1 - Description of problem or function: HAARM3, an acronym for Heterogeneous Aerosol Agglomeration Revised Model 3, is the third program in the HAARM series developed to predict the time-dependent behavior of radioactive aerosols under postulated LMFBR accident conditions. HAARM3 was developed to include mechanisms of aerosol growth and removal which has not been accounted for in the earlier models. In addition, experimental measurements obtained on sodium oxide aerosols have been incorporated in the code. As in HAARM2, containment gas temperature, pressure, and temperature gradients normal to interior surfaces are permitted to vary with time. The effects of reduced density on sodium oxide agglomerate behavior and of nonspherical shape of particles on aerosol behavior mechanisms are taken into account, and aerosol agglomeration due to turbulent air motion is considered. Also included is a capability to calculate aerosol concentration attenuation factors and to restart problems requiring long computing times. HAARM-S: This is a development of the HAARM-3 code with the follow- ing specific features: - The computational speed is increased by a factor of 5 by using an improved integration method for 'stiff' differential equations. - The model can handle up to 15 sequential compartments. - A granular filter can be handled by dividing the bed into a number of zones. - The atmosphere can consist of a mixture of air and steam. - The input data have been divided into logical groups with a block head for each group. 2 - Method of solution: HAARM3 assumes the time-dependent particle size distribution is log-normal and coverts the integro-differential equation describing the concentration decay of aerosol into three first-order differential equations which are integrated using a standard library subroutine. The present model allows the method of integration to be specified. The choices are: Adams Moulton with either a fixed or variable step-size and Runge-Kutta with a fixed step-size. 3 - Restrictions on the complexity of the problem: Maxima of: 1000 time-steps, 42 discrete radii for the distribution calculations