Experimental Study on Cooling Characteristics of Mixed Particle Size Debris Bed under Different Water Injection Methods
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摘要: 液态堆芯熔融物与冷却剂相互作用（FCI）后破碎形成颗粒床，对颗粒床实施有效的冷却可以实现熔融物的滞留并终止事故进程。本文基于原型熔融物FCI实验后的碎片粒径分布和孔隙率，构建了带内热源的混合粒径砂石碎片床，对不同碎片床强化排热措施（顶部淹没水池、自然循环驱动底部注水、周向进水）下的干涸特性进行了研究，实验中发现：顶部淹没水池条件下，碎片床的中上部率先出现汽泡壅塞区，随后在碎片床中下部出现缺液干涸区；自然循环驱动底部注水条件下，极大改善了碎片床底部的缺液状态，干涸热流密度（DHF）提升2.5倍以上，干涸区域位于碎片床中上部；周向进水方式下，DHF也提升2.5倍以上。
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关键词:
- 严重事故 /
- 堆内滞留 /
- 碎片床 /
- 干涸热流密度（DHF）
Abstract: The liquid core melt interacts with the coolant and breaks into a particle bed. Effective cooling of the particle bed can realize the retention of the melt and stop the accident process. In this paper, based on the particle size distribution and porosity of the fragments after the prototype molten FCI experiment, a mixed particle size sand debris bed with internal heat source was constructed, and the dryout characteristics of the debris bed under different enhanced heat removal measures (submerged pool at the top, water injection at the bottom driven by natural circulation, and circumferential water inlet) were studied. The results show that, under the condition of submerged pool at the top, the bubble clogging zone appears first in the middle and upper part of the debris bed, and then the liquid deficiency dryout zone appears in the middle and lower part of the debris bed. Under the condition of water injection at the bottom driven by natural circulation, the fluid deficiency at the bottom of the debris bed was greatly improved, and the dryout heat flux (DHF) increased by more than 2.5 times, the dryout area was located in the middle and upper part of the debris bed. Under the circumferential water inlet, DHF also increased by more than 2.5 times.-
Key words:
- Severe accident /
- In-vessel melt retention /
- Debris bed /
- DHF
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图 2 电加热元件和光纤测温点分布
Figure 2. Distribution of Temperature Measuring Points of Heating Element and Optical Fiber
图 3 工况7中的汽泡壅塞区和缺液干涸区温度变化
Figure 3. Temperature Changes for Bubble Choked Area and Liquid Dryout Area in Condition 7
图 4 工况7干涸区域的轴向和径向位置
Figure 4. Axial and Radial Positions of Dryout Area in Condition 7
图 5 工况4干涸区域的轴向和径向位置
Figure 5. Axial and Radial Positions of Dryout Area in Condition 4
图 6 工况14干涸区域的轴向和径向位置
Figure 6. Axial and Radial Positions of Dryout Area in Condition 14
表 1 DBC实验主要干涸实验工况与结果
Table 1. Main Dryout Experienment Conditions and Results for DBC Experienment
实验工况编号 碎片床结构 进水方式 碎片床高度/m 水池高度/m 系统压力/MPa 干涸时加热功率/kW 干涸区域位置 干涸热流密度/(kW·m−2) 1 均匀床 顶部淹没 1.0 0.6 0.14 67.9 Tf5、Tf6、Tf4、Tf3 667.075 4 均匀床 顶部淹没 1.0 1.0 0.3 86.5 Tf4 849.809 7 均匀床 顶部淹没 1.0 0.6 1.0 124.5 Tf5、Tf4、Tf3 1223.14 10 均匀床 顶部淹没 1.0 0.6 0.2 73.3 Tf7、Tf5、Tf6 720.127 13 均匀床 双下降管 1.0 1.0 0.18 129.5 Tf15、Tf14 1272.26 14 均匀床 双下降管 1.0 1.0 0.3 165.2 Tf15、Tf14 1622.99 16 均匀床 单下降管 1.0 1.0 0.2 >185.6(未烧干涸) — >1823.4 30 均匀床 周向进水 1.0 1.0 0.2 >189.5(未烧干涸) — >1823.4 Tf—分布式光纤测温传感器轴向的测温点标号；“—"—没有干涸区域 
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