Preliminary Investigation on Natural Circulation Flow using CFD and Calculation Base on Experimental Data Pre-FASSIP-02

One of the most important aspects of nuclear safety systems is the reactor cooling system, both in under normal conditions and in accident conditions. Severe accident occurrences due to the failure of the active cooling system, led to the growing importance of the role of passive cooling systems to be implemented in current and future reactor safety systems, in particular. Passive cooling system experiments conducted to understand and determine what parameters affect the natural circulation flow rate, especially local phenomena that occur. So the purpose of this study was conducted to investigate the effects of temperature changes on cold areas and hot area to circulation flow using CFD software and the results of calculations from the experimental data. The experiments were carried out using a facility called the Pre-FASSIP-02 strand, most of which was composed of transparent materials, especially on pipes and heating parts. CFD simulations are also performed to predict the flow rate occurring in natural circulation cases. The analysis was done using water temperature in the near of heater inside water tank which was heated-up during 75 minutes from 26°C in average until 72°C. The result shows that natural circulation flow was increase from -0.035 m/s to 0.218 m/2 using calculation base on experiment data, and using CFD, the flow increased from -0.038 m/2 to 0.327 m/s. The deviation of natural circulation flow between CFD and calculation results are 9.74% for the lower value and 33.17% for the higher value.