Numerical Simulation And Study On Heat Transfer Of The Different Fuel Rods In Pressurized Water Reactor (PWR)

The reactor core is an important part of the nuclear power plants. The most essential issues of the nuclear power safety that need to be addressed is to ensure the heat generated by the core can be taken away effectively in time. The numerical research on changing of source terms and temperature field changes has been done using unstructured grid and FORTRAN program during different stages of the operation.Based on the one-group diffusion theory of uniform medium, the different boundary conditions and the geometry size (cylinder and six-rowed column) are taken to consider and discuss the effect on temperature distribution within the fuel rods. During the analysis, per unit volume of heat release rate and per unit area of heat dissipation was used at the same time, that was because of the inner temperature is higher in cylinder one than that of six-rowed column. The change of boundary conditions has no effects on the inner temperature distribution expect the maximum temperature changes as well as the ends of rod. The maximum temperature under adiabatic boundary condition is higher than that of fixed temperature boundary condition.The temperature distribution within the fuel rods was calculated during different stages of the operation. On the initial stage, neutron flux density reaches its maximum level while the control bar has not worked. The distribution along the axis follows the law of cosines. As the equilibrium temperature is higher than that in the normal operating conditions, it’s great importance to make sure that the fuel rods’maximum temperature is not over the fuel rods security limits. The brief analysis of the changes of the temperature field was made when the fuel rods heat release rate changes with the change of temperature and time. The result shows that the introduction of a negative reaction in the reactor leads to a temperature reduce and stabilized at the safe state.On the other hand, the core with reflective layer and bare core were compared with integrated approach. The results show that the reflecting layer contributes the increase of temperature. With the increase in thickness of reflective layer, the increase speed of temperature drops. The core temperature fields are almost the same no matter the boundary is constant temperature or adiabatic, expect at the ends of fuel rod. What’s more, the maximum temperature level has no difference and will not affect the judgment of the nuclear reactor security.Finally, based on the second Law of Thermodynamics, the system entropy is studied. And, more research on heat transfer process within the fuel rods has been made also. Three cases were used to verify the correctness of the program and research. Then, we have the discussion and analysis on the heat transfer process of the heat generated in the fuel rods, with a combination of the temperature distribution form. More research on the enhancement of the heat transfer process of the fuel rods could be finished.