As revealed by Fukushima Daiichi nuclear disaster, countermeasures against severe accident in nuclear power plants are an urgent need. In particular, from the viewpoint of protecting containment and suppressing the diffusion of radioactive materials, it is important to develop the device which allows filtered venting of contaminated high pressure gas. In the filtered venting system that used in European reactors, so called Venturi scrubbers are used to realize filtered venting without any power supply. The Venturi scrubber operates without a power supply of high pressure gas filled into the containment. In this apparatus, scrubbing of contaminated gas is promoted by both gas releases through a submerged Venturi tube which is one of the major components of Venturi scrubber and liquid splay flow formed by liquid suction through a hole for suction provided at the throat part of the Venturi tube. This type of Venturi scrubbers is called self-priming ones. However, the mechanism of a self-priming Venturi scrubber including effects of gas flow rate and shape of Venturi tube is understood insufficiently in the previous studies.

In this study, to provide knowledge about the detailed mechanism of filtering and evaluation method for operating condition of the filtered venting system with Venturi scrubber, both experimental and numerical research works have been performed. In this paper, as a previous step of designing and making a self-priming Venturi tube, hydraulic behavior in a rectangular Venturi tube is taken by high speed camera, by the air-water experiment under atmospheric condition to check the operation in a self-priming mode and the validity of the experimental method and the visualization technique. And numerical analysis of a circular Venturi tube is conducted as a preliminary analysis, by TPFIT (Two-Phase Flow simulation code with Interface Tracking) to predict its operation. As results, the Venturi scrubbers used in experiment and simulated in numerical analysis were operated in a self-priming mode. By observed results of the hydraulic behaviors in the Venturi tube, the validity of the experimental method and the visualization technique were confirmed. And it is expected that the simulated circular Venturi scrubber in this numerical simulation was operated in a self-priming mode in a real situation.

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