چكيده لاتين
The Miniature Neutron Source Reactor of Isfahan is a research, thermal, and intrinsically safe reactor. This reactor is low-power and of the tank-pool type. It has highly enriched fuel, water as a coolant and moderator, and beryllium as a reflector. Heat transfer in this reactor is carried out by free convection flow. The reactor tank serves as a good barrier and protection against the reactor core from the external environment and vice versa, and therefore it is important. One of the incidents that may occur to the reactor tank is the formation of a hole in the tank. Since heat is extracted in the reactor through water, the presence of a hole in the tank affects the thermal-hydraulic of the reactor. Therefore, in this study, the effect of the presence of a hole on the thermal-hydraulic of the reactor and its operating time has been investigated. To do this, a computational fluid dynamics analysis has been carried out using ANSYS Fluent software. First, the reactor geometry and specifications were collected, and then the complete reactor geometry, including fuel rods, dummy rods, control rods, bottom, top, and side reflectors, reactor tank, and pool, was modeled and then meshed. The reactor power was applied to the fuel rods in the form of power density and the simulation was run for 3600 seconds. First, the normal operation of the reactor was examined. The simulation data were in good agreement with the experimental data. The reactor operation time in the normal mode was found to be 4782.21 seconds. Then, two modes without the tank and without the bottom part of the tank were examined. In the no-tank mode, the inlet and outlet fluid temperatures increased very slightly and the mass flow rate of the core outlet was obtained to be almost constant, so the reactor operation time in this mode can be assumed to be infinite. In the case without the bottom part of the tank, the inlet and outlet fluid temperatures increased less than in the normal reactor operation mode but the mass flow rate leaving the reactor core was decreasing, so the reactor shut down. Then, at three heights of 10 cm, 23 cm, and 250 cm, circular holes with diameters of 1 cm, 3 cm, and 5 cm were considered, and the reactor operation time was obtained. In general, the presence of a hole in the tank increases the reactor operating time, but this increase depends on the location and diameter of the hole. On average, the presence of holes at heights of 10 cm, 23 cm, and 250 cm increases the reactor operating time by 13.6%, 17.6%, and 16.8%, respectively. The largest increase in reactor operating time is 23.2% in a hole with a diameter of 5 cm and a height of 23 cm. The smallest increase in reactor operating time is 7.3%, related to a hole with a diameter of 1 cm and a height of 10 cm.
