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Communication Dans Un Congrès Année : 2021

Experimental and numerical studies of gaseous and particulate pollutants backflow through an opening from a depressurized enclosure: application to nuclear dismantling operations

Résumé

During nuclear maintenance and dismantling operations, a dynamic confinement due to inflow passing through openings is applied in order to prevent the leakage of pollutants from depressurized enclosures. This ensures better safety for operating people. To guaranty an efficient dynamic confinement, three values for the velocity of the inward flow near the opening were required in the past, depending on the dangerousness of the radioactive pollutants. Nowadays the ISO standard (ISO, 2004) advises to study every situation independently from the other (Lafanechere, 2009). However, some aeraulic environments induced by activities inside the enclosure (such as countercurrent blowing works facing the opening) could generate local and temporary flow reversals near the opening which would then lead to leaks of pollutants outward the enclosure. Preliminary laser visualizations (Figure 1) have shown that the presence of an additional countercurrent turbulent jet flow in competition with the mean inward flow is among the main causes of backflow through the opening. The main purposes of this work are to detect and measure experimentally the backflow of gaseous and particulate pollutants to outside the depressurized enclosure induced by a countercurrent jet. It aims also at verifying the ability of CFD (Computational Fluids Dynamics) simulations to predict these flow inversions near the opening by using SST-DES turbulent model. Experiments were performed on an enclosure with small opening (0.03 × 0.1) 〖cm〗^2 on its frontal wall. Gas and particles tracing techniques highlight and contribute to quantify the backflow phenomenon near the opening. Experimental results show that the behavior of the gaseous and particulate pollutants (aerosol of aerodynamic diameter 5 microns) is similar in terms of backflow magnitude near the opening. CFD results (Figure 2) confirmed the reliability of the hybrid model SST-DES to quantify the backflow phenomenon near the opening. This model has been successfully compared to experimental results on gaseous and particulate leakage. We found that in addition to the ISO recommendations on the inflow velocity at the opening, a new aeraulic criterion based on the disturbance and the inflow velocities ratio at the opening should be taken into account to ensure an efficient confinement. The perspectives of this work are to perform experiments on a real depressurized airlock, while varying the disturbance type (countercurrent or parietal jet, inside or outside the enclosure, disturbance related to the motion of an external obstacle..). Simultaneously, we aim to test the ability of numerical simulations to predict the backflow phenomenon at this scale.
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hal-03427122 , version 1 (12-11-2021)

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  • HAL Id : hal-03427122 , version 1

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Zeinab Rida, Eric Climent, Corinne Prevost, Thomas Gelain. Experimental and numerical studies of gaseous and particulate pollutants backflow through an opening from a depressurized enclosure: application to nuclear dismantling operations. European Aerosol Conference, EAC2021, Aug 2021, VIRTUAL, United Kingdom. ⟨hal-03427122⟩
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