Study on Failure Mechanism of Pressurizer Surge Line and Manhole Structure under LOCA
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摘要: 稳压器是核反应堆进行压力控制和保护的重要设备，冷却剂丧失事故（LOCA）产生的巨大冲击可能造成其关键部位的结构失效。通过多场耦合计算方法，对小破口LOCA下稳压器波动管的流动传热和结构应力、人孔结构的温度分布和密封性能进行了三维瞬态数值模拟，分析了其失效机理。结果表明：高温流体快速流入波动管形成了巨大的瞬时载荷，造成了管道短时间的强烈振动，管道中间部位变形最大，可能破坏管道支撑结构；各部位等效应力快速增大，与主管道的接管部位出现了集中应力现象，较大的应力波动会影响其寿命；人孔结构出现较大的温度分布不均匀性，密封结构下垫片的密封性能变化最大，在100 s前后其内、外侧密封面接触压力都降至设计密封比压值以下，即出现泄漏。本文根据分析结果提出了波动管和人孔结构的改进建议，可为船用核动力装置发生小破口LOCA后的事故缓解提供技术借鉴。Abstract: Pressurizer is an important equipment for pressure control and protection in nuclear reactors, and the huge shock generated by loss of coolant accident (LOCA) may cause structural failure of its critical parts. The three-dimensional transient numerical simulation of pressurizer surge line’s flow heat transfer and structural stress, the temperature distribution and sealing performance of manhole structure under the small break LOCA are carried out by the multi-field coupling method, and the failure mechanism is analyzed. The results show that the hot fluid rapidly flowing into the surge line forms a huge instantaneous load, causing a short period of strong vibration of the pipe, the middle part of the pipe deformation is the largest, which may destroy the pipe support structure; The equivalent stress of each part increases rapidly, and concentrated stress occurs at the connecting pipe part of the main pipe. Large stress fluctuation will affect its service life; The manhole structure has a large uneven temperature distribution, and the sealing performance of the gasket under the sealing structure changes the most. The contact pressure of the inner and outer sealing surfaces drops below the design sealing specific pressure before and after 100 seconds, which means leakage occurs. According to the analysis results, this paper puts forward some suggestions for improving the structure of surge line and manhole, which can provide technical reference for accident mitigation after small break LOCA in marine nuclear power plant.
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Key words:
- Marine nuclear power plants /
- LOCA /
- Pressurizer surge line /
- Manhole structure /
- Failure mechanism
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图 4 不同网格数量下弯管1内外壁面温差
Figure 4. Temperature Difference between Inner and Outer Walls of Elbow 1 with Different Grid Numbers
图 6 不同网格数量下上垫片最大温差
Figure 6. Maximum Temperature Difference of Upper Gasket with Different Grid Numbers
图 8 波动管靠稳压器侧流体流量变化
Figure 8. Variation of Fluid Flow of Surge Line near the Pressurizer Side
图 9 波动管与主管路接口靠压力容器侧流体流量和温度变化
Figure 9. Variation of Fluid Flow and Temperature on the Side of Pressure Vessel at the Interface between Surge Line and Main Pipeline
图 10 波动管各部位内壁面温度分布
Figure 10. Temperature Distribution on the Inner Wall of Surge Line’s Each Part
图 11 波动管各部位内外壁面温差变化
Figure 11. Changes of Temperature Difference between Inner and Outer Walls of Surge Line’s Each Part
图 13 接管部位内外壁面温差变化
Figure 13. Changes of Temperature Difference between Inner and Outer Walls at Nozzle
图 15 弯管3在X、Y、Z方向位移变化
Figure 15. Displacement Variation of Elbow 3 in X, Y and Z Directions
图 16 弯管3在X、Y、Z方向位移振动频域图
Figure 16. Vibration Frequency Domain Diagram of Displacement of Elbow 3 in X, Y and Z Directions
图 17 压力和温度波动对弯管3在X方向位移的影响
Figure 17. Influence of Pressure and Temperature Fluctuation on Displacement of Elbow 3 in X Direction
图 19 接管部位出口侧沿厚度方向等效应力分布
Figure 19. Equivalent Stress Distribution along Thickness Direction at Outlet Side of Nozzle
图 20 波动管各部位最大等效应力变化
Figure 20. Maximum Equivalent Stress Change of Each Part of Surge Line
图 22 上、下垫片最大温差变化
Figure 22. Maximum Temperature Difference between Upper and Lower Gaskets
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