Study on Gravity Sedimentation of Multicomponent Hygroscopic Aerosols in Reactor Severe Accident
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摘要: 严重事故时，安全壳内的多组分吸湿性气溶胶将在高湿度的条件下吸水增大，从而影响其重力沉降行为。通过理论分析，本文推导了多组分吸湿性气溶胶颗粒平衡粒径的物理模型，并通过实验结果进行验证。该模型重点关注溶解度对吸湿过程的影响，解释了多组分吸湿性颗粒粒径增大曲线不连续的原因。同时，分析了典型千兆瓦级压水堆核电厂中相对湿度、干粒径及非吸湿性组分质量分数对重力沉降去除系数的影响。结果表明，只有当气溶胶颗粒增大到一定程度后，其重力沉降速度才会明显的提高；对于干粒径超过0.01 μm的纯吸湿性气溶胶颗粒，只有超过一定湿度后其才会因吸湿而加速沉降，且该湿度下限随着干粒径的增大而减小；随着事故的进行，气溶胶颗粒中的非吸湿性组分质量分数逐渐增加，上述湿度下限将增加，且同湿度下吸湿对重力沉降的促进作用减弱。Abstract: In the event of a severe accident, the multicomponent hygroscopic aerosols in the containment will absorb water under the high humidity condition, thereby influencing the gravity sedimentation behavior. In this study, a physical model of the equilibrium particle diameter of the multicomponent hygroscopic aerosol particles was developed through theoretical analysis, and it was also validated by experimental results. The model focuses on the effect of solubility on the hygroscopic process and explains the reason why the multicomponent hygroscopic particles grow along a discontinuity curve. Based on a typical gigawatt-class pressurized water reactor, the effects of relative humidity, dry particle diameter and mass fraction of hygroscopic components on the removal coefficient of the gravity sedimentation were investigated. The results show that the velocity of the gravity sedimentation will significantly increase, only if the aerosol particles grow to a certain degree. Only when the humidity is more than a certain value, the sedimentation process of the pure hygroscopic aerosol particles with a dry particle diameter exceeding 0.1 μm will accelerate due to hygroscopicity, and this humidity limit will decrease as the dry particle diameter increases. With the progress of the accident, the mass fraction of non-hygroscopic components in the aerosol particles gradually decreases, leading the above-mentioned humidity limit increasing and the acceleration of gravity sedimentation due to the hygroscopicity decreasing in the same humidity.
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Key words:
- Severe accident /
- Gravity sedimentation /
- Hygroscopic aerosol /
- Multicomponent /
- Solubility
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图 1 气溶胶颗粒中有2种吸湿性组分时函数aw(dp)与函数g(dp)的示意图
Figure 1. Schematic Diagram of Function aw(dp) and Function g(dp) when Aerosol Particle Contains two Components
图 2 KCl和NaCl组成的多组分颗粒的相对质量随相对湿度的变化
Figure 2. Relative Mass of Multicomponent Particle Including KCl and NaCl Changing with Relative Humidity
图 3 干粒径为1 μm的多组分CsI与CsOH气溶胶颗粒的相对粒径和相对去除系数随相对湿度的变化
Figure 3. Relative Particle Diameters and Relative Removal Coefficients of Multicomponent CsI and CsOH Aerosol Particles with Dry Particle Diameter of 1 μm Changing with Relative Humidity
图 4 多组分CsI与CsOH气溶胶颗粒的相对去除系数随相对湿度和干粒径的变化
Figure 4. Relative Removal Coefficients of Multicomponent CsI and CsOH Aerosol Particles Changing with Relative Humidity and Dry Particle Diameters
图 5 干粒径为1 μm的多组分气溶胶颗粒的相对去除系数随相对湿度和BaO质量分数的变化
Figure 5. Relative Removal Coefficients of Multicomponent Aerosol Particles with the Dry Particle Diameter of 1 μm Changing with Relative Humidity and Mass Fraction of BaO
表 1 1100 MW压水堆中不同核素的堆芯积存量
Table 1. Inventories of Different Elements in a Typical 1100 MW Pressurized Water Reactor
物质 来源 积存量/kg UO2 燃料 1.00×105 Zr 包壳 2.00×104 Sn 包壳 3.00×102 Fe 结构材料 2.50×103 I 裂变产物 1.80×101 Cs 裂变产物 2.55×102 Ba 裂变产物 4.16×102 Ru 裂变产物 3.18×102 Zr 裂变产物 2.76×102 
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