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DIspersion of Simulated COrium-Cold

Fr. Dr. Xiaoyang Gaus-Liu

Programme: Nuclear Waste Management, Safety and Radiation Research (NUSAFE)

Research on Severe Accidents in Light Water Reactors (LWR). Investigation of the fluid-dynamic processes during melt ejection out of a breach in the lower head of a LWR pressure vessel, at pressures below 2 MPa and various failure modes with cold model fluids.

 

Experiments are performed in a scaled annular cavity design (1:18), to investigate melt dispersal from the reactor pit when the reactor pressure vessel lower head fails at low system pressure of less than 2 MPa. The fluid dynamics of the dispersion process is studied using model fluids, water or bismuth alloy instead of corium, and nitrogen or helium instead of steam. The effects of different breach sizes and locations, and different failure pressures on the dispersion are studied, specifically by testing central holes, lateral holes, horizontal rips, and complete ripping of the bottom head.
The experimental results have shown, that the failure mode of the lower head plays a predominant role in the dispersion process. It has also been observed, that even at low system pressures large amounts of melt can be carried out of the cavity in form of a liquid film that flows up at the cavity wall into the compartments as well as in form of dispersed droplets. In some experiments, drop sizes as well as drop and liquid jet velocities were measured.