IVR-ERVC下压水堆压力容器下封头传热及应力/应变分析
|
摘要
以某1000 MW压水堆为例,利用二维极坐标热模型分析RPV壁面与双层堆芯熔池和外部冷却水堆腔之间的传热,计算下封头壁面瞬态二维温度场分布和烧蚀情况,同时通过有限元分析程序计算下封头壁面的各瞬态温度场和烧蚀引起的热应力/应变情况,分析压水堆RPV下封头在压力容器内熔融物滞留-压力容器外冷却(IVR-ERVC)下的结构完整性。计算结果表明:(1)芯熔融坍塌后200 s下封头壁面开始熔融,最薄厚度直线下降;3000 s后熔融区沿下封头内壁呈一片柳叶形状分布;(2)下封头内表面的吸热热流大于外表面的散热热流,在两层熔池界面处内外表面热流密度达到最大值;(3)RPV下封头热应力在0～400 s时集中于下封头内壁面;在400s后,下封头内壁面热应力逐渐减小,形变量逐渐增大,下封头完整性可以得到保证;(4)2000 s以后,RPV下封头烧蚀损伤处内外壁面均产生应力集中,下封头烧蚀处内外壁应力值均大于许用应力,在2000 s后有可能发生断裂,在烧蚀损伤边缘处可能出现破口。
Taking a 1000 MW PWR as an example, a two-dimensional polar coordinate thermal model was used to analyze the coupling heat transfer among the wall surface of RPV, the two-layer melting core pool and the outer water chamber. The transient 2 D temperature and ablation of the bottom head wall surface were calculated. At the same time, the finite element analysis program was used to calculate the thermal stress and strain caused by the transient temperature field and ablation of the wall of the lower head. The thermal stress/strain condition was used to analyze the structural integrity of the PWR RPV lower head in the pressure vessel under the In-vessel retention via external reactor vessel cooling(IVR-ERVC). The calculation results show that:(1)The wall of the lower head began to melt at 200 s after the core collapsed, and the thinnest thickness decreased linearly. After 3000 s, the molten zone along the inner wall of the head formed a lancet shape distribution.(2)The endothermic heat flux of the inner surface of the lower head was larger than that of the external surface, and the heat flux reached the maximum value at the interface between the two layers of the molten pool.(3)The strain of RPV lower head increased sharply in the period from 0 s to 400 s and then keeps unchanged. The equivalent stress locally concentrated on the inner wall of the lower head at 400 s. After 400 s, the inner wall thermal stress decreased gradually, the shape variable increased, and the integrity of the lower head could be guaranteed.(4)After 2000 s, the stress concentration was generated on the inner and outer wall at the ablation of the RPV lower head. The stress value of the inner and outer walls of the lower head was greater than that of allowable stress. The RPV lower head may fail at any time after 2000 s and may be broken at the edge of the ablation area.
Taking a 1000 MW PWR as an example, a two-dimensional polar coordinate thermal model was used to analyze the coupling heat transfer among the wall surface of RPV, the two-layer melting core pool and the outer water chamber. The transient 2 D temperature and ablation of the bottom head wall surface were calculated. At the same time, the finite element analysis program was used to calculate the thermal stress and strain caused by the transient temperature field and ablation of the wall of the lower head. The thermal stress/strain condition was used to analyze the structural integrity of the PWR RPV lower head in the pressure vessel under the In-vessel retention via external reactor vessel cooling(IVR-ERVC). The calculation results show that:(1)The wall of the lower head began to melt at 200 s after the core collapsed, and the thinnest thickness decreased linearly. After 3000 s, the molten zone along the inner wall of the head formed a lancet shape distribution.(2)The endothermic heat flux of the inner surface of the lower head was larger than that of the external surface, and the heat flux reached the maximum value at the interface between the two layers of the molten pool.(3)The strain of RPV lower head increased sharply in the period from 0 s to 400 s and then keeps unchanged. The equivalent stress locally concentrated on the inner wall of the lower head at 400 s. After 400 s, the inner wall thermal stress decreased gradually, the shape variable increased, and the integrity of the lower head could be guaranteed.(4)After 2000 s, the stress concentration was generated on the inner and outer wall at the ablation of the RPV lower head. The stress value of the inner and outer walls of the lower head was greater than that of allowable stress. The RPV lower head may fail at any time after 2000 s and may be broken at the edge of the ablation area.
引文
[1]Theofanous T G,Liu C,Additon S,et al.In-vessel coolability and retention of a core melt[J].Nuclear Engineering and Design,1997,169(1-3):1-48.
[2]Krieg R,Devos J,Caroli C,et al.On the prediction of the reactor vessel integrity under severe accident loadings(RPVSA)[J].Nuclear engineering and design,2001,209(1):117-125.
[3]Koundy V,Durin M,Nicolas L,et al.Simplified modeling of a PWR reactor pressure vessel lower head failure in the case of a severe accident[J].Nuclear engineering and design,2005,235(8):835-843.
[4]Lim K,Cho Y,Whang S,et al.Evaluation of an IVR-ERVC strategy for a high power reactor using MELCOR 2.1[J].Annals of Nuclear Energy,2017,109:337-349.
[5]Abendroth M,Willschütz H G,Altstadt E.Fracture mechanical evaluation of an in-vessel melt retention scenario[J].Annals of Nuclear Energy,2008,35(4):627-635.
[6]金越,刘晓晶,程旭,等.严重事故下大功率先进压水堆IVR-ERVC有效性分析[J].核科学与工程,2016,36(01):116-124.
[7]Mao J F,Zhu J W,Bao S Y,et al.Study on structural failure of RPV with geometric discontinuity under severe accident[J].Nuclear Engineering&Design,2016,307:354-363.
[8]张小英,姚婷婷,李志威,等.堆芯熔融物对压力容器壁面烧蚀过程的数值模拟[J].核技术,2015,38(02):93-98.
[9]李维特,黄保海.热应力理论分析及应用[M].中国电力出版社,2004.
[10]张俊善.材料的高温变形与断裂[M].科学出版社,2007.
[11]武敏,谢龙汉.ANSYS Workbench有限元分析及仿真[M].电子工业出版社,2014.
[12]刘飞,韩利战,顾剑锋,等.A508-3核电大锻件用钢连续冷却贝氏体的相变塑性[J].材料热处理学报,2013,34(02):32-36.
[13]Sehgal B R,Theerthan A,Giri A,et al.Assessment of reactor vessel integrity(ARVI)[J].Nuclear Engineering and Design,2003,221(1):23-53.
[2]Krieg R,Devos J,Caroli C,et al.On the prediction of the reactor vessel integrity under severe accident loadings(RPVSA)[J].Nuclear engineering and design,2001,209(1):117-125.
[3]Koundy V,Durin M,Nicolas L,et al.Simplified modeling of a PWR reactor pressure vessel lower head failure in the case of a severe accident[J].Nuclear engineering and design,2005,235(8):835-843.
[4]Lim K,Cho Y,Whang S,et al.Evaluation of an IVR-ERVC strategy for a high power reactor using MELCOR 2.1[J].Annals of Nuclear Energy,2017,109:337-349.
[5]Abendroth M,Willschütz H G,Altstadt E.Fracture mechanical evaluation of an in-vessel melt retention scenario[J].Annals of Nuclear Energy,2008,35(4):627-635.
[6]金越,刘晓晶,程旭,等.严重事故下大功率先进压水堆IVR-ERVC有效性分析[J].核科学与工程,2016,36(01):116-124.
[7]Mao J F,Zhu J W,Bao S Y,et al.Study on structural failure of RPV with geometric discontinuity under severe accident[J].Nuclear Engineering&Design,2016,307:354-363.
[8]张小英,姚婷婷,李志威,等.堆芯熔融物对压力容器壁面烧蚀过程的数值模拟[J].核技术,2015,38(02):93-98.
[9]李维特,黄保海.热应力理论分析及应用[M].中国电力出版社,2004.
[10]张俊善.材料的高温变形与断裂[M].科学出版社,2007.
[11]武敏,谢龙汉.ANSYS Workbench有限元分析及仿真[M].电子工业出版社,2014.
[12]刘飞,韩利战,顾剑锋,等.A508-3核电大锻件用钢连续冷却贝氏体的相变塑性[J].材料热处理学报,2013,34(02):32-36.
[13]Sehgal B R,Theerthan A,Giri A,et al.Assessment of reactor vessel integrity(ARVI)[J].Nuclear Engineering and Design,2003,221(1):23-53.