<p style="margin: 0mm">In Boiling Water Reactors (BWRs), in order to evaluate the behavior of the coolant inside the fuel bundle, the cross-flow phenomenon has been focused on so far. In the previous studies of the cross-flow phenomenon for two subchannels, it was pointed out that the turbulent mixing rate correlated with the magnitude of the differential pressure fluctuation (DPF) between two subchannels, and the behavior of the DPF has well been studied with the experiments and the simulations. Generally, the DPF between two subchannels is derived from the difference between the pressure fluctuation of one subchannel and that of the other subchannel. This means that, to understand the behavior of the DPF, it is also important to clarify that of the pressure fluctuation in a subchannel. Therefore, we have performed the two-phase flow test in a subchannel which simulates the structure in a BWR fuel rod bundle. In the test facility, the time-averaged void fraction (TVF) is measured by the three-dimensional X-ray computed tomography system, and the pressure fluctuation is obtained by the piezoelectric pressure transducer for measuring the instantaneous pressure. With using this test facility, we obtained the relationship between the TVF and the magnitude of the pressure fluctuation in a subchannel and confirmed that the magnitude of the pressure fluctuation depended on the TVF. Also, we investigated the behavior of the pressure fluctuation for the pressure and for the size of the occupied space by the two-phase flow. The obtained results showed that, under the constant TVF, the magnitude of the pressure fluctuation became small with increasing the pressure or with expanding the occupied space by the two-phase flow. This work was partly conducted as a government-commissioned project of Agency for Natural Resources and Energy, Technology development for common ground maintenance to contribute to nuclear safety enhancement in 2016 and in 2018 (Research and development for understanding two-phase flow behavior inside a fuel bundle)”.</p>

Behavior of the Pressure Fluctuation of the Two-Phase Flow in a Subchannel

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

2021 28th International Conference on Nuclear Engineering (ICONE28)

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