Since the occurrence of the Fukushima-Daiichi nuclear plant accident, severe accident (SA) measures have become a public issue. In the considerable scenarios of SAs, the core meltdown occurs, and molten corium falls into a coolant pool of lower plenum. It is considered that the molten corium jet is atomized, cooled, and solidified with fuel-coolant interaction (FCI). In the viewpoint of safety, estimating a cooling behavior of corium is required. The FCI process contains three phenomena, jet-breakup, heat transfer, and phase change. In especially, the jet-breakup is significantly important, because the jet shape affects heat transfer and phase change directly. Thereby, an evaluation method of molten corium jet-breakup behavior using TPFIT has been developed. Besides, it is needed to clarify the mechanism of FCI for validation of the analysis code.&nbsp;Several studies have been conducted to understand the jet-breakup phenomena of test liquids. Although they succeeded in suggesting the prediction relation of jet-breakup length, according to some scenarios, the pool depth would be shallow owing to accumulation of leakage. In this situation, it is considered that jet impinges the bottom of a pool without breakup. In previous research, by using a 3D-LIF method, the 3D Jet shape data in a shallow pool were obtained. However, the quantification of the liquid film and the fragmentation has not been conducted.&nbsp;The purpose of this study is to clarify the mechanism of the liquid jet behavior in a shallow pool. In this paper, we discuss the spreading behavior of the liquid jet in a shallow pool. The jet injection experiment with four initial velocity conditions was conducted using test fluids. Using by 3D-LIF method, unsteady three-dimensional jet shape data was obtained, and the 3D reconstraction of the liquid jet was conducted. From visualization result the following behaviors was seen. After bottoming, the jet spread with the liquid film and, the liquid film was rolled up to the indside of liquid film at the tip of the liquid film. We call this flow recirculation flow. After a certain time, the recirculation flow was broken, and the deposition was occurred at the tip. The break of the recirculation flow can influence the number density of the fragment and the distribution of the surfacearea which are important element for estimating the heat transfer in the real machine.In the future, the number density of the fragment and the surfacearea will be discussed.

Liquid Film Behavior of Bottoming Liquid Jet in a Shallow Pool Measured by 3d-Lif

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.