Sodium-cooled fast reactor and related multiphase flow phenomena, 2; Evaluation of gas entrainment phenomena by free surface vortex

Ezure, Toshiki 

In the design of sodium-cooled fast reactors (SFR), cover gas entrainment at the free surface inside the reactor vessel is one of the key thermal-hydraulic issues. Cover gas entrained into the coolant behaves as non-condensable gas and can disturb core reactivity while passing through the core. In addition, a large amount of entrained gas may degrade the heat transfer performance at heat exchangers. Therefore, fast reactor design usually requires suppression of gas entrainment and control of the total amount of non-condensable gas bubbles entrained into the primary coolant system. This paper presents an evaluation approach based on numerical analyses for cover gas entrainment phenomena in SFRs, including an evaluation method for gas entrainment induced by free-surface vortices using the evaluation tool StreamViewer and an analysis method for the transport behavior of non-condensable gases within the primary coolant system using the SYRENA code.