Experimental study of buoyancy driven exchange flow from breaches under LOVA condition

Using a preliminary LOVA apparatus which simulated a vacuum vessel of the fusion reactor with a small-scaled model, the buoyancy-driven exchange flow behavior through breaches between the inside (filled with helium gas) and the outside (air)of the vacuum vessel was investigated quantitatively under atmospheric temperature condition. The present experimental results clarified that the exchange flow rate was independent of the breach locations in the vacuum vessel and depended on strongly the magnitude of the potential energy from the ground level. In a single breach case, the exchange flow receives the effect of a counter-current flow through the breach. On the other hand, in a double breach case, since a one-through now path between two breaches is produced, the exchange flow rate is much larger than that of the single breach case