Fission deposition onto aerosols

The extent of these interactions will be determined not only by the chemical and physical forms of the volatilized materials and by the prevailing ambient conditions, but also by the availability of the required reaction partners. Obviously, it is unreasonable to suppose that the chemical forms of any element would necessarily remain unaffected by the numerous changes in bulk physical and chemical conditions, or by interaction with other fission products and inactive materials (Bowsher, 1987). The products of chemical reactions of volatile fission products with aerosols or with structural surfaces often show reduced volatility on the other hand, highly volatile species may be formed, for example as a result of the decomposition of Csl induced by such reactions. Upon deposition onto the surfaces of... 

In any case, deposition of volatile fission products onto the surfaces of other aerosols will influence significantly their transport behavior and, consequently, their source term to the containment. Because of their great importance, such vapor-aerosol interactions in the primary system have been extensively studied at many institutions. However, investigations on a laboratory scale are very difficult to perform in such a way that their results can be meaningfully transferred to a full-scale facility. 

The kinetics of chemical interactions between fission product vapor and aerosols is mainly controlled by gas phase mass transport, by the kinetics of the chemical reaction, and by mass transport in the condensed phase. Another factor potentially influencing the kinetics of vapor deposition is that the heat liberated by condensation or by chemical reaction of vapor with aerosol must be disposed of. Because of their small masses, aerosol particles have only limited capacity for conducting away this heat, compared with the structures within the reactor coolant system. This problem may arise particularly in the deposition of water vapor onto aerosol particles which have been previously covered by hygroscopic or water-soluble compounds such as CsOH. 

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