Experimental and numerical research on melting behavior mechanism of fuel rod using MPS-CV method

Experimental and numerical study was conducted to investigate the behavior of fuel elements and substitute material under severe fuel damage (SFD) accident conditions. The Fuel Rod Melt Progression Apparatus (FROMA) in XJTU make it possible to visualize many key phenomena during severe accident, such as eutectic melting, mass and temperature distribution of fuel rod, migration and relocation of molten material. In this paper, the melting behavior mechanism of fuel rod was studied using the new developed moving particle semi-implicit (MPS) method, which is called as MPS-CV. CV is the abbreviation of Control Volume method, and MPS-CV is a particle-grid hybrid method based on MPS method and Finite Volume Method (FVM). In this method, the momentum conservation equation was solved by MPS method and the energy conservation equation was solved by FVM. Therefore, MPS-CV solves the convective heat transfer problems exactly. MPS-CV method has been validated with the experimental data from FORMA. Results show that the melting behavior of nuclear reactor fuel rod at high temperature can be easily simulated using the MPS-CV method. The research reveals the mechanism of fuel rod behavior under severe accidents and reduces the uncertainty of existing accident analysis codes.