[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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A damage reduction system against hydrogen explosions in nuclear power-generator buildings is proposed, and its current development is reported. The system consists of a flame arrester made of fine-mesh wire screens and an explosion air bag. Flames are extinguished by the flame arrester, and the expanding unburned gas mixture is held inside the air bag. The explosion air bag prevents the dispersion of radioactive substances into the atmosphere and reduces the pressure rise inside the building. The basic design and specifications of the system, demonstrations by small scale experiments, field experiments using a 125-liter reinforced concrete explosion vessel, and development of flame arresters are provided.

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Recently, many disasters in petrochemical plants such as tank fires and explosions have been taking place, thus it is required to reconfirm the safety for such plants. In the case of pool fires in large tanks, it is mentioned in a past study that oil tanks which are not filled up may be more dangerous than full tanks. But previous methods which estimates the dangerous areas of burning tanks does not consider effects of oil level and black smoke. The purpose of the study is to construct a new evaluation method which estimates heat radiation from burning tanks while considering the effects of the oil level and black smoke. We employed CFD analysis in order to estimate tank fires in detail. But analyzing vast areas by CFD needs a large amount of time and it is difficult to construct the models. So we used CFD analysis to get the tank fireʼs distribution of heat radiation in the vertical direction. We can consider the effects of the oil level and black smoke by using the distribution. We then apply it to a flame model used in an evaluation method based on the Monte Carlo method. This way, we can construct the new method which solves conventional problems and is able to estimate dangerous areas of the burning tanks easily. The result of this evaluation analysis which uses the proposed method showed that the dangerous area extended a maximum of 40％ if the oil tanks are not filled up. The proposed method is very effective in cases where the oil tank is not filled.

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