Preliminary Numerical Study of Hot Water Layer Temperature on Flow Stratification in Pool of Open-pool Type Research Reactor

A research reactor provides multi-purpose utilization of neutron sources such as radio-isotopes production, irradiation operation, and so on. In this type of research reactor, the reactor core is submerged in the lower part of the pool to provide core cooling and reactor safety. Therefore, the water in the lower part of the pool is highly radioactivated and is heated up by the core as well. If natural circulation occurs in the pool due to the heat from the core, the radioactivated water can rise to the surface of the pool where numbers of workers and researchers are nearby. To solve this problem, a Hot Water Layer (HWL) is often implemented in the upper part of the pool to reduce the radiation level on the pool top. The HWL is maintained at a sufficiently higher temperature than the lower part of the pool to produce a thermally stratified region in the middle part of the pool, which suppresses the natural circulation. In this study, the flow and temperature distributions in the pool are investigated by preliminary numerical simulations. The effects of HWL temperature on flow stratification are further studied by changing the discharge temperature of the hot water in the upper part of the pool. The basic design of the on-going KIJANG research reactor (KJRR) project is considered in this study using commercial computational fluid dynamics software ANSYS FLUENT 13.0