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Possible improvements of the aerosol resuspension model of ECART in the light of VTT tests

pubblicazioni - Articolo

Possible improvements of the aerosol resuspension model of ECART in the light of VTT tests

Il lavoro rientra nelle attività allestite nel contesto del Network Europeo SARNET, svolta in collaborazione con il centro finlandese VTT. Il progetto di riferimento RdS è il Nucleare.

Steam generator tube rupture (SGTR) is one of the potential accidents which can lead to a significant source term. In fact, both primary and secondary circuits run through the steam generators and it is possible that a radioactivity release from the reactor core by-passes the containment structure by leaking to the secondary circuit through possible pipe breaks. To evaluate the possible source term of such accidents, it is crucial to estimate the retention efficiency of radiotoxic species that can be transported in form of aerosol throughout the steam generator tubes. In order to study the deposition and resuspension processes of fine particles, VTT Technical Research Centre of Finland performed experiments of aerosol deposition and resuspension in a typical tube. The tests were carried out with three different nickel powders that formed monolayer deposits that were resuspended by gas flow at increasing rate steps. The paper presents an analysis of these tests using the aerosol models of the code ECART and highlights the characteristics of the obtained aerosol deposits. The code models show a good estimation of the aerosol deposition in laminar condition, while an underestimation of the total deposited mass occurs in the case of turbulent flow. Regarding the resuspension, the results show that the simulation code overestimates the phenomenon, being based on experimental data related to multi-layer deposits only. An explanation of these discrepancies is given, and improvements of the deposition and resuspension models presently running within ECART are proposed in order to take into account any dependence of resuspension rate on the number of layers actually involved.

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