STUDY ON THE EFFECTS OF DIFFERENT COOLANT SALTS ON THE CHARACTERISTICS OF NATURAL CIRCULATION OF MOLTEN SALT REACTOR USING COMPUTATIONAL FLUID DYNAMICS

• Main Author: Humam
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/63065
• Institution: Institut Teknologi Bandung

Energy is a really important resource for humanity. As the number of population grows, so does the energy need. Nuclear Power Plant (NPP) is a type of power plant that uses nuclear reaction to generate energy. Molten Salt Reactor or MSR is one of the Generation IV nuclear reactors, a type of NPPs with enhanced safety and efficiency. MSR utilizes the use of molten salt as both its fuel and coolant, which makes it unique compared to other types of NPP. Natural circulation is a phenomenon in which fluid that has a temperature gradient on certain points, can promote flow naturally, so convection may occur. The temperature gradient on certain points will cause density variation in the fluid system, which will result in the existence of thermal driving head that causes the fluid to flow. Natural circulation is an important factor in ensuring the safety of a nuclear reactor in the event of a disaster, for example the loss of pump power. In this research, study on the thermalhydraulics aspect, which is an aspect that studies the transfer and distribution fo heat, was conducted on the secondary coolant loop of MSR. This study was done by means of simulation using a computational fluid dynamics software. The software that was used is an open-source software OpenFOAM which uses the finite volume method. The natural circulation, one of the inherent safety systems of generation IV nuclear reactor, was simulated. Three types of molten salt were used in this study to see the difference between the two molten salts. The molten salts that were used are (formula)(FLiNaK), (formula)(FLiBe), and (formula)(FnaBe). The solver that was used is buoyantSimpleFoam, a steady-state solver for compressible turbulent buoyant fluid flow. The Boussinesq Approximation was used for the density calculation. The simulation was ran for 7200 iterations, with a step of 20 iterations. The heater and coolant temperatures were made constant, with values of 973 K and 803 respectively. The initial fluid temperature was 873 K. The temperature of the system was evaluated in four different points, right after exiting the heater, before entering the cooler, right after exiting the cooler, and before entering the heater. The simulation results showed that natural circulation occured in all three molten salt systems. The temperature value after exiting the heater experienced an increase, while the temperature of fluid after exiting the heater experienced a decrease, which proved that the natural circulation occured caused by difference in temperature. FNaBe system had the highest final temperature, followed by FLiBe and FLiNaK. FLiNaK had also reached saturation temperature at around 884 K. As for the flow velocity, the opposite is true, with FLiNaK having the higehst flow velocity followed by FLiBe and FNaBe. The difference in temperature is caused by the difference in flow velocity. FNaBe with the lowest flow velocity was able to take heat better. This velocity difference is caused by the difference in the thermal driving head, which stemmed from the difference in the density difference between the hot and cold regions. FLiNaK had the highest rate of density change over temperature, and therefore had the highest density difference between the cold and hot regions, resulting in higher thermal driving head, and consequently higher flow velocity. Variation on the heat source temperature and geometry height also affected the final temperature and flow velocity for all three systems.