Modelling of a CO2-gas jet into liquid-sodium following a heat exchanger leakage scenario in Sodium Fast Reactors

A numerical model for the CO2–sodium chemical interactions in Sodium Fast nuclear Reactors

“…The boundary layer thickness of a 20 m size droplet has been estimated equal to 3 m, for a droplet slip velocity order of magnitude consistent with values numerically found in underexpanded gas-into-liquid jets (Vivaldi et al, 2013). In the bubbly-flow regime, the reaction takes place inside the CO 2 bubble, where vapor sodium diffuses.…”

“…8 shows the calculated sodium mass fraction profile inside the bubble, for a sodium temperature of 973 K and a pre-exponential factor of 1 × 10 9 m 3 (mol s) −1 (the value of the activation energy is supposed equal to 4 × 10 4 J mol −1 ). The initial bubble radius is 0.4 mm, a typical order of magnitude of bubble diameters inside underexpanded gas-into-liquid jets, as found by Vivaldi et al (2013). It can be observed how all the sodium vapor is consumed by the reaction in a very narrow region.…”

“…As an example, results are reported for an initial droplet diameter of 20 m (which is the order of magnitude found by Epstein et al (2005) for gas injection pressures up to 1.2 MPa), a droplet slip velocity of 20 m s −1 (mean value calculated by Vivaldi et al (2013) along the region where the droplet reaction is supposed to take place, for a gas injection pressure of 0.7 MPa), a pre-exponential factor equal to 1 × 10 9 m 3 (mol s) −1 . The choice of employing this value of the pre-exponential factor as the example for the present paper, comes from the fact that negligible mass fraction profile variation, inside the droplet boundary layer, were found for pre-exponential factors lower than 1 × 10 9 m 3 (mol s) −1 .…”

“…Liquid entrainment inside underexpanded gas-intoliquid jets have been recently experimentally investigated and confirmed by Epstein et al (2005) and Kudoh et al (2013). Starting from a certain point downstream the leakage outlet, the gas core breaks up into small gas bubbles: this behavior have been experimentally observed by Vivaldi et al (2013). Therefore, two different CO 2 -Na contact typologies can be distinguished inside the considered jet: sodium droplet surrounded by CO 2 , for the mist flow region, and CO 2 bubble surrounded by liquid sodium, for the bubbly flow region.…”

“…In the bubbly-flow regime, the reaction takes place inside the CO 2 bubble, where vapor sodium diffuses. A bubble size of 0.4 mm has been retained, a typical size evaluated through critical Weber number and numerical results of underexpanded gas-into-liquid jets (Vivaldi et al, 2013). The thickness of the corresponding boundary layer, where the reaction takes place, is 2 m (see Fig.…”