Numerical Study on Passive Control of Thermal Striping Phenomenon Using Lorentz Force in Fast Reactor

Liquid sodium, used as a coolant of fast reactor (FR), is an electromagnetic fluid. When a magnetic field is embedded to liquid sodium flow, the Lorentz force will be induced and flow structure such as a turbulent mixing phenomenon will be influenced. In a FR piping system, thermal fatigue is one of key issues that may occur after a piping junction of different fluid temperature. In the present paper, a numerical study of sodium flow induced by the Lorentz force on a turbulent mixing after the junction has been carried out. The large eddy simulation (LES) coupled with the electromagnetic field analysis is used for this purpose. The governing equations of the electric density field and the magnetic flux density fields are solved separately so that the solenoidal condition is satisfied non-iteratively. The fractional step method is applied to the present coupling in the simulation. As a result of the numerical investigation, it is demonstrated that the temperature fluctuation due to turbulent mixing weakens after it runs through the magnetic field caused by the Lorentz force and thus the thermal fatigue will be suppressed. Accordingly, it is concluded that the passive control of the thermal fatigue will be possible by adding a magnetic field.