热预应变对反应堆压力容器材料断裂行为影响研究

Research on Thermal Pre-strain Effect on the Fracture Behavior of Reactor Pressure Vessel Materials

压水堆核电站反应堆压力容器(RPV)辐照脆化问题是制约其长期安全服役的主要因素,现有的美国ASME和法国RCC-M规范尚未充分考虑RPV用钢(铁素体材料)的热预应力(WPS)对断裂评价的有益影响。针对某RPV材料(16 MND 5),采用标准CT试样进行室温加载(L)、保持载荷降低测试温度(C),最后加载直至断裂(F)的测试方案(LCF的测试过程)。试验结果表明,在LCF的最后低温断裂阶段,RPV材料实际断裂韧度为基于RCC-M规范预测结果的两倍左右,也明显高于主曲线预测的断裂失效概率为95%对应的材料断裂韧度。因此,在RPV寿期末的脆性断裂评价中,考虑WPS效应会显著提高其安全性能评估裕量。

The reactor pressure vessel’s(RPV) irradiation embrittlement in pressurized-water reactor nuclear power plant troubles its safe and long-term service. The existing ASME and French RCC-M codes fails to take into account the effect of RPV steel’s(ferrite material) thermal pre-stressing(WPS) on the fracture evaluation. For a certain RPV material(16 MND 5), the standard CT specimen were loaded at room temperature(L), and then the load was kept and test temperature(C) was reduced, and finally the specimen was loaded until it fractured(F)(LCF test process). The experimental results show that, the actual fracture toughness of the RPV material at the LCF’s last low-temperature fracture stage is about twice that predicted by the RCC-M specification, and it is significantly higher than that of the material with 95% fracture probability predicted by the main curve. Therefore, taking into account the effect of WPS in the evaluation of brittle fracture of RPV at the end of life can significantly improve safety performance’s evaluation margin.