Kinetic model to describe the behaviour of the I/Cs/Ag/Cd/H(2)O/H(2) system in the primary circuit of PWRs under severe accident conditions
The interactions between silver and cadmium aerosol and gaseous fission product species in a PWR primary system in case of severe accident have been studied in this work from a kinetic point of view. The final objective was to have a kinetic model able to describe, as realistically as possible, the processes occurring in a flowing system that contains steam, hydrogen, iodine and caesium vapours and silver and cadmium aerosol. The influence of the pipe wall has also been considered. The work included justifications for the selection of the chemical reactions considered more important between aerosol and gaseous fission product species, the estimation of the rate constants of such reactions using Wagner's theory, mass transfer considerations and available experimental results, the implementation of such rate constants into a kinetic model previously developed (which included only gaseous fission product species) and some input examples that show the utility of the resulting model. Moreover, condensation aspects and variable temperature have also been introduced. It has been concluded that to consider mass transfer from the gas bulk to the aerosol surface as the limiting step for this sort of process could be inaccurate in some accident sequences. Moreover, to consider thermochemical equilibrium to model such processes could be a poor approximation.
Bibliographic Reference: EUR 15212 EN (1993) 62 pp., FS, free of charge
Availability: Available from Joint Research Centre, Publication Department, I-21020 Ispra (Va.) (IT)
Record Number: 199511570 / Last updated on: 1995-12-12
Original language: en
Available languages: en