Experimental and numerical analysis of impingement temperature effect on the sacrificial plate's hole formation during nuclear severe accident

Abstract

Liquid metal breaching onto a metal plate is an important aspect that needs to be considered in the nuclear severe accident analysis. This relates to the downward relocation of molten material to the supporting system such as sacrificial grid plate and lower head while accident happened. The molten core material impinged the sacrificial grid plate which was quenched before interacted with reactor pressure vessel. The present study aims to investigate the dynamic behaviors of holes formation due to liquid metal jet impingement onto a metal plate at initial temperatures 423 K, 473 K, and 523 K. The experiments and numerical simulation were performed with molten Wood's Metal and 5 mm thickness of Lead Bismuth Eutectic plates. The modified Moving Particle Semi-Implicit method was used to perform the numerical calculation based on the particle movement. The results showed that the plate was locally melted by the heat supplied from the liquid metal jet and induced the penetration. A larger amount of liquid metal stayed, then liquid metal pool was formed when the liquid temperature jet was lower. The temperature variation resulted unsignificant change of hole size diameter on both surfaces. The formed hole sizes in the plate's top and bottom surfaces were around 5.7–14 mm and 3.7−5 mm, respectively. The required time for the liquid metal penetration was shorter when the liquid metal temperature was higher. The increase of conduction heat transfer during the solidification of liquid metal could decrease the Nusselt number at the stagnation zone. The findings show that the experiment and numerical results can predict the sacrificial grid plate's hole formation and dynamic mechanism within critical time of molten core material impingement.