ARTICLE:

• Experiments on Vessel Hole Ablation During Severe Accidents  download article

B. Raj Sehgal
Nuclear Power Safety, Royal Institute of Technology, 100 44 STOCKHOLM, Sweden

Jonas Andersson
Nuclear Power Safety, Royal Institute of Technology, 100 44 STOCKHOLM, Sweden

Nam Dinh
Nuclear Power Safety, Royal Institute of Technology, 100 44 STOCKHOLM, Sweden

Ann Bui
Nuclear Power Safety, Royal Institute of Technology, 100 44 STOCKHOLM, Sweden

Timo Okkonen
Nuclear Power Safety, Royal Institute of Technology, 100 44 STOCKHOLM, Sweden

ABSTRACT

A program of simulant material experiments has been initiated at the Division of Nuclear Power Safety, to investigate the physical processes that occur during the core melt attack on the reactor vessel, and the containment, during the progression of a severe accident. The simulant materials are mixtures of oxides, which melt from 900 K to 1500 K, form crusts and have low viscosity. Specific experiments planned, in the initial program, are on (a) the interaction of melt and vessel and (b) interactions of melt and water.
The first set of experiments on melt vessel interactions, performed with a simulant melt mixture containing PbO and B₂ 0₃, employ a lead plate as a simulant for vessel wall. The process studied is that of ablation, as the melt is discharged to the containment through the vessel failure location. Preliminary data have been obtained for plates of 20, 30 and 40 mm thickness each with an initial hole of 10 mm diameter. Scaling analysis has been performed and a one dimensional code HAMISA has been completed. A two dimensional code has also been prepared, since it has been observed that the ablation process is two dimensional.
A preliminary set of experiments on melt-water interaction were performed with small quantities of molten PbO, and water at several values of subcooling. The fraction of melt fragmented varied with the subcooling magnitude.

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