Discharge capacity requirements of severe accident depressurization valves
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摘要: 二代加百万千万级核电站严重事故下卸压过程中高温流体流经卸压阀,可能造成流道变形,甚至造成阀杆下落使得排放流道封闭,造成卸压失败。对严重事故专用卸压阀在卸压过程中可能经历的高温流体状态进行谱分析,获得了不同卸压能力下阀门经受的高温流体状态。开展了高温可能引起的阀门流道变形对卸压效果的影响分析。第二类阀门虽然存在阀门流道变形的可能,但能够获得较长严重事故处置时间,从优化严重事故对策的角度,严重事故专用卸压阀推荐采用第二类阀门排放能力450~600 t/h范围。
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关键词:
- 高压熔堆 /
- 熔融物喷射 /
- 反应堆冷却剂系统卸压 /
- 严重事故卸压阀 /
- 高温流体
Abstract: In the process of depressurization during severe accidents for the second generation nuclear power plant, high temperature fluid flowing through the severe accident depressurization valves may cause deformation of the valve body or even cause the valve stem to fall down because of being heated by high temperature fluid, resulting in depressurization failure. In this paper, the spectrum analysis of the high temperature fluid state that the depressurization valve may experience in the process of pressure relief is carried out, and the high temperature fluid state under different pressure relief capacities is obtained. The influence of the valve channel deformation caused by high temperature on the depressurization effect is studied. Although the second type valve has the possibility of valve channel deformation, it can obtain a longer time window for severe accident mitigation. From the perspective of optimizing the severe accident measures, the discharge capacity range of the second type valve 450-600 t/h is recommended. -
表 1 事故主要进程时间节点
Table 1. Accident process of depressurization
case time/s pressure/MPa open valves: Tout
(reactor is 50 ℃)accumulator
injectionpressurizer
drainaccumulator
drainTout of pressurizer
≥1000 ℃RPV lower
head failureRPV lower
head failurecase 1-0: 350 t/h 5750 6515 6575 12825 6625/18605 20925 1.39 case 2-0: 450 t/h 5750 6350 6550 12600 18145 18800 0.78 case 3-0: 600 t/h 5750 6200 — 6750 — 15425 0.99 case 4-0: 1000 t/h 5750 6000 12375 6500 12410 14000 0.90 表 2 事故主要进程时间节点(阀门开启初期发生流道变形)
Table 2. Accident process of depressurization with valve channel deformation
valve channel deformation(350 t/h:6625 s) time/s pressure/MPa accumulator drain RPV lower head failure RPV lower head failure case 1-1:25% 15565 22300 1.35 case 1-2:50% 15980 26650 2.32 case 1-3:75% 21050 31700 4.14 case 1-4:90% — 13300 7.62 表 3 事故主要进程时间节点(事故后期发生流道变形)
Table 3. Accident process of depressurization (with late valve channel deformation)
valve channel deformation time /s pressure/MPa 350 t/h:18605 case 1-5:25% 19400 1.27 case 1-6:50% 19410 1.56 case 1-7:75% 19415 2.04 case 1-8:90% 19400 2.51 450 t/h:18145 case 2-1:25% 18875 0.91 case 2-2:50% 18880 1.11 case 2-3:75% 18865 1.45 case 2-4:90% 18890 1.93 1000 t/h 13010 case 4-1:25% 14000 1.52 case 4-2:50% 14075 2.51 case 4-3:75% 14150 3.82 case 4-4:90% 14000 4.78 -
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