EXCHANGE FLOW CHARACTERISTICS IN A TOKAMAK VACUUM VESSEL OF FUSION-REACTOR UNDER THE LOSS-OF-VACUUM CONDITIONS

When a Tokamak vacuum vessel of fusion reactor is broken, buoyancy-dri ven exchange flows will take place through breaches after the inside p ressure of the vacuum vessel (VV) becomes equal to the outside pressur e. The exchange flow may bring a mixture of activated dusts and tritiu m from the inside of the VV to the outside through the breaches. Moreo ver, the exchange flow may remove decay heat from the plasma-facing co mponents. A preliminary LOVA (Loss Of VAcuum event) apparatus was cons tructed to investigate quantitative heat transfer characteristics of t he exchange flows through the breaches under the LOVA conditions. The results of this study, the relationship between Froude numbers and bre ach locations in the VV was determined and empirical correlations for the average Froude numbers were derived.