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Following a severe nuclear accident, boiling phenomena in the reactor pit pool may occur due to decay heat from fission products or pressure-relief processes. This could lead to steam-driven entrainment of radioactive aerosol-laden droplets into the containment atmosphere, thereby posing secondary radioactive release risks. To quantify droplet entrainment behavior and optimize source term assessment methodologies within containment vessels, this study established a large-scale experimental system (volume: 12.5 m3, height: 5.2 m). Systematic experiments investigating droplet entrainment characteristics were conducted in a 2-bar pure steam environment using potassium iodide (KI) as a soluble tracer. The entrainment factor was determined through gaseous tracer sampling and concentration analysis, with comprehensive investigation of the effects of pool tracer concentration (0.36–5.62 g/L) and superficial gas velocity on entrainment dynamics. Additionally, the applicability of classical models for predicting entrainment factors in deposition-controlled regimes was critically evaluated. Experimental results revealed that the entrainment factor (E ≈ 10−5–10−4) exhibited no significant correlation with the pool tracer concentration. However, the absolute entrainment quantity demonstrated a positive dependence on increasing tracer concentrations. When the superficial gas velocity increased from 0.55 to 3.31 cm s−1, the entrainment factor increased by one order of magnitude. This enhancement was primarily attributed to intensified turbulence and enhanced gas–liquid interfacial momentum transfer. In model evaluation, compared to Kataoka-Ishii model, the Cosandey’s model demonstrated superior accuracy in describing entrainment behavior within deposition-controlled regimes. Nevertheless, when experimental parameters exceeded the model’s validated ranges—particularly under elevated Weber numbers and reduced tracer concentrations—the predictive capability of the Cosandey’s model became constrained, typically yielding underestimations.

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Experimental Study of Droplet Entrainment Characteristics in Boiling Liquid Pools

  • 会议论文

  • 发表日期：

    2026年

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  • Jianqun Yu,
  • Haifeng Gu,
  • Jawaria Ahad,
  • Yanmin Zhou,
  • E. Xinnuo

摘要

Following a severe nuclear accident, boiling phenomena in the reactor pit pool may occur due to decay heat from fission products or pressure-relief processes. This could lead to steam-driven entrainment of radioactive aerosol-laden droplets into the containment atmosphere, thereby posing secondary radioactive release risks. To quantify droplet entrainment behavior and optimize source term assessment methodologies within containment vessels, this study established a large-scale experimental system (volume: 12.5 m3, height: 5.2 m). Systematic experiments investigating droplet entrainment characteristics were conducted in a 2-bar pure steam environment using potassium iodide (KI) as a soluble tracer. The entrainment factor was determined through gaseous tracer sampling and concentration analysis, with comprehensive investigation of the effects of pool tracer concentration (0.36–5.62 g/L) and superficial gas velocity on entrainment dynamics. Additionally, the applicability of classical models for predicting entrainment factors in deposition-controlled regimes was critically evaluated. Experimental results revealed that the entrainment factor (E ≈ 10−5–10−4) exhibited no significant correlation with the pool tracer concentration. However, the absolute entrainment quantity demonstrated a positive dependence on increasing tracer concentrations. When the superficial gas velocity increased from 0.55 to 3.31 cm s−1, the entrainment factor increased by one order of magnitude. This enhancement was primarily attributed to intensified turbulence and enhanced gas–liquid interfacial momentum transfer. In model evaluation, compared to Kataoka-Ishii model, the Cosandey’s model demonstrated superior accuracy in describing entrainment behavior within deposition-controlled regimes. Nevertheless, when experimental parameters exceeded the model’s validated ranges—particularly under elevated Weber numbers and reduced tracer concentrations—the predictive capability of the Cosandey’s model became constrained, typically yielding underestimations.