Numerical analysis of melt penetration behavior in the control rod drive housing of Fukushima Daiichi Nuclear Power Station Unit-2

Li, X. ; Yamaji, Akifumi*; Sato, Ikken*; Yamashita, Takuya  ; Nagae, Yuji 

For Fukushima Daiichi Nuclear Power Station (1F) Unit-2, the muon radiography investigation results indicate that the fuel debris are largely retained inside the RPV. The current study focuses on the analysis of metallic melt penetration behavior in the CRD housing with Moving Particle Semi-implicit (MPS) method. A three-dimensional CRD housing model with simplified inner structures was established. The injection of SS-Zircaloy eutectic melt into the CRD housing was simulated and its downstream penetration and freezing behavior under vertically varying temperature boundary conditions was analyzed. It is found that the melt would start to freeze and form channel blockages soon after it enters the region with a relatively cold boundary in the downstream.