Study on simulation code for dilute bubble flow

In a sodium-cooled fast reactor, inert gas exists in the primary coolant system as bubbles or dissolved gas. Such inert gas may cause disturbance in reactivity and/or degradation of IHX performance, and therefore, the inert gas behaviors have to be investigated to ensure the stable operation of a fast reactor. Similarly, small bubbles exist also in the mercury target loop in J-PARC to suppress cavitation erosion. Those small bubbles should be removed immediately at the downstream of a target region because the small bubbles may accumulate at the upper plenum of a heat exchanger and degrade the heat exchange efficiency. To simulate these inert gas behaviors in liquid metal flows, the Japan Atomic Energy Agency (JAEA) has developed a plant dynamics code VIBUL. In this study, new models, i.e. the bubble release and bubble carry under models, are introduced to simulate the bubble behaviors in the fast reactor and mercury target system. Then, the small bubble behavior in the mercury target system is simulated to check the validity of the new models. (author)