Numerical Study on the Potential of Cavitation Damage in a Lead–Bismuth Eutectic Spallation Target
Abstract
:1. Introduction
2. Configuration of LBE Spallation Target Head
3. Heat Deposition in LBE
4. Numerical Simulation Models
4.1. Model for Calculating Dynamics of Pressure Waves
4.2. Computational Fluid Dynamics (CFD) Analysis Model
5. Results and Discussions
5.1. Cavitation Damage due to Pressure Waves
5.1.1. Time Response of Pressure
5.1.2. Threshold of Cavitation Damage Initialization
5.1.3. Cavitation Bubble Expansion for LBE Spallation Target
5.2. Cavitation Damage due to LBE Flow
5.2.1. Steady-State Flow
5.2.2. Transient Flow
6. Conclusions
- The intensity of pressure waves generated in the LBE was found to be weak due to the relatively long duration of the proton beam pulse. Therefore, the expansion ratio of the cavitation bubbles due to the pressure waves, was only 1.4, which was considerably lower than the threshold ratio that could lead to severe cavitation damage on the vessel.
- The magnitude of maximum negative pressure had a second power law relationship with the flow speed of the HLM. For the nominal inlet flow speed of 0.125 m/s, the negative pressure induced by the steady-state LBE flow was only −0.013 MPa, which was considerably smaller than the cover gas pressure of the LBE spallation target; therefore, this pressure could not drive the growth of the cavitation bubbles.
- For the transient LBE flow, negative pressure was generated in the LBE, due to a decrease in LBE flow velocity. Under normal target operation conditions, the duration of negative pressure was too short to drive the growth of adequately large cavitation bubbles. However, cavitation might have occurred under a few extreme flow variation conditions, for example, when the rate of change in inlet flow was higher than 0.2 m/s2, even as the initial inlet flow speed was 0.25 m/s.
- The maximum cavitation bubble dynamics due to turbulent flow in an orifice could be classified into two stages. In the first stage, the maximum cavitation bubble expansion ratio shared a power law relationship with the inlet flow speed, but it was almost independent of the inlet flow speed change rate; in the second stage, the maximum cavitation bubble expansion ratio shared, a power law relationship with, both, the inlet flow speed and the rate of change in the inlet flow speed.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Physical Properties | Symbol | Unit | 316 SS | LBE |
---|---|---|---|---|
Density | kg/m3 | 7908 | 10450 | |
Young’s modulus | MPa | 1.742 × 105 | 92.8 | |
Poisson’s ratio | - | 0.3153 | 0.4995 | |
Thermal expansion coefficient | K−1 | - | 1.285 × 10−4 |
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Wan, T.; Naoe, T.; Kogawa, H.; Futakawa, M.; Obayashi, H.; Sasa, T. Numerical Study on the Potential of Cavitation Damage in a Lead–Bismuth Eutectic Spallation Target. Materials 2019, 12, 681. https://doi.org/10.3390/ma12040681
Wan T, Naoe T, Kogawa H, Futakawa M, Obayashi H, Sasa T. Numerical Study on the Potential of Cavitation Damage in a Lead–Bismuth Eutectic Spallation Target. Materials. 2019; 12(4):681. https://doi.org/10.3390/ma12040681
Chicago/Turabian StyleWan, Tao, Takashi Naoe, Hiroyuki Kogawa, Masatoshi Futakawa, Hironari Obayashi, and Toshinobu Sasa. 2019. "Numerical Study on the Potential of Cavitation Damage in a Lead–Bismuth Eutectic Spallation Target" Materials 12, no. 4: 681. https://doi.org/10.3390/ma12040681