辐照后N18锆合金氢致延迟开裂临界温度预测

PREDICTION OF CRITICAL TEMPERATURE FOR DELAYED HYDRIDE CRACKING IN IRRADIATED N18 ZIRCONIUM ALLOY

基于辐照后锆合金中H的固溶与析出浓度方程及应力诱导H扩散方程,建立了辐照后锆合金氢致延迟开裂(DHC)临界温度的预测模型.采用此模型对辐照后N18锆合金(Zr-Sn-Nb)的DHC临界温度进行预测,并与未辐照N18锆合金临界温度实验数据进行对比分析.结果表明,中子辐照后N18锆合金屈服强度和H的固溶度增加,N18合金发生DHC的敏感性增加;相同H含量条件下,辐照后N18合金的临界温度最高上升幅度接近20℃;辐照后N18锆合金临界温度变化规律与未辐照实验结果相似,其临界温度介于相同H含量下完全固溶的温度与氢化物析出时的温度之间,且最高开裂温度T_c低于最低止裂温度T_h.

Delayed hydride cracking（DHC）has been recognized as a potential threat to the structural intcgrity of zirconium alloy components in water-cooled nuclear reactors since the early 1970 s.Although DHC has been studied for a long time,most of the investigations were focused on unirradiated Zr-Nb and Zr-Sn alloys,no information was found on Zr-Sn-Nb alloy. Currently,several new Zr-based alloys have been developed from the point of view of enhancement of corrosion resistance and hydrogen pickup properties.In China,N18（Zr-Sn-Nb）alloy has been developed based on Zr-Sn and Zr-Nb systems to meet the requirements of higher fuel burn-up.Therefore,it is necessary to investigate the DHC behavior of N18 alloy systematically. The objective of this study is to predict the critical temperatures for initiating and arresting DHC in irradiated N18 alloy.A model used to forecast DHC critical temperature of irradiated zirconium alloys was established based on the terminal solid solubility of hydrogen in irradiated zirconium alloys and stress-induced hydrogen diffusion.By using the model,the critical temperatures for irradiated N18 alloy were predicted.The result showed that the irradiated N18 alloy has high sensitivity for DHC initiation,because neutron irradiation increased the solubility of hydrogen and yield strength of N18 alloy.Compared with unirradiated N18 alloy,the critical temperature of irradiated N18 alloy rise nearly 20℃.The variation of critical temperatures of irradiated N18 alloy is similar to the unirradiated one.T_c is slightly less than T_h.