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Ueda, Hayate*; Asahara, Makoto*; Kamiya, Tomohiro
no journal, ,
Vapor explosions occur when the thermal energy of a molten metal droplet immersed in water is rapidly converted into mechanical energy. The metal droplet breakup promotes this conversion and thus has a significant influence on explosion behavior. In this study, optical visualization and pressure measurements were performed in vapor explosion experiments with a single droplet. The results confirmed the generation of pressure waves associated with the breakup, and data contributing to the development of vapor explosion models were obtained.
Ueda, Hayate*; Asahara, Makoto*; Kitagawa, Kazutaka*; Miyasaka, Takeshi*; Kamiya, Tomohiro
no journal, ,
A vapor explosion is a unique explosive phenomenon that occurs due to the rapid interaction between molten material and coolant. It is a concern during severe accidents in nuclear reactors and can also contribute to the escalation of damage during submarine volcanic eruptions. The strong pressure waves generated in the initial stages are believed to propagate while affecting the surrounding molten material; however, their propagation characteristics are not yet fully understood. In this study, experiments were conducted in which a single molten metal droplet was dropped into water, and the pressure waves generated by spontaneous vapor explosion were measured using pressure sensors and a high-speed camera.
Ueda, Hayate*; Kamiya, Tomohiro; Asahara, Makoto*
no journal, ,
In a steam explosion caused by the penetration of molten metal into water, shock waves and pressure waves with rapid pressure rises are generated, leading to damage in the surrounding area. The collapse of the vapor film is expected to generate pressure waves from multiple molten metal fragments and amplify them. These pressure wave propagation mechanisms are complex, and clarifying the mechanism of initial pressure wave generation from a single droplet is an important task for accurate prediction and evaluation. Therefore, this study focuses on the steam explosion phenomenon involving a single molten metal droplet. In this presentation, we report the results of visualizing the behavior of the steam explosion generated from a single molten metal droplet and measuring the associated pressure waves.
Kamiya, Tomohiro; Ueda, Hayate*; Asahara, Makoto*
no journal, ,
In a vapor explosion, molten material is dispersed in the water, and the pressure waves interact with the molten material and with other pressure waves, eventually forming the final pressure wave. Because such pressure wave propagation processes are complex, a detailed understanding through simulation is expected. The pressure waves originate from the rapid pressure increase caused by the abrupt phase change. Additionally, a vapor explosion involves a multiphase flow in which water, vapor, and molten material coexist, and it is necessary to handle the interfaces accurately. We modeled the pressure increase due to phase change and incorporated it into an interface capturing scheme suitable for detailed analysis. We will report the results of a single droplet vapor explosion simulation.
Kamiya, Tomohiro; Ueda, Hayate*; Asahara, Makoto*
no journal, ,
It is important to understand the propagation structure of pressure waves generated by vapor explosions, which are considered as one of the severe accident scenarios. To this end, we are developing a vapor explosion model applicable to an interface-capturing method that can accurately and faithfully handle flows with interfaces. In this presentation, numerical simulations of vapor explosions involving a single molten tin droplet are performed, and the sensitivity of various parameters of the vapor explosion model to the predicted pressure waves is investigated.