用正电子湮没技术研究新锆合金包壳的离子辐照效应

Study on Ions Radiation Effect of New Zr Alloy by Positron Annihilation Technique

国产Zr-Sn-Nb系新锆合金SZA-4和SZA-6是CAP1400大型先进压水堆包壳材料的主要候选材料,对其辐照性能的研究可为制备工艺改进提供科学依据。在中国原子能科学研究院HI-13串列加速器辐照终端,在300℃温度下,用100MeV的Fe束流对两种新锆合金包壳管材进行5dpa剂量辐照。辐照前后的正电子湮没寿命测量表明:两种样品辐照前湮没寿命为Zr中单空位寿命,表明管材制备过程中最后的退火温度和时间尚未完全消除加工引入的缺陷;两种样品辐照后的正电子湮没寿命减小,分析表明这是由于辐照导致Fe在锆合金中重新分布,主要分布在bcc结构的β-Nb沉淀相颗粒与hcp结构的α-Zr基体之间具有开空间的相界,正电子被相界捕获,与周围Fe原子电子湮没,造成湮没寿命减小。

Domestic Zr-Sn-Nb type new zirconium alloy SZA-4 and SZA-6 are the main candidate materials for cladding of CAP1400 advanced pressurized water reactor.The study of the radiation effects could provide the scientific evidence for the improvement of preparation technics.Utilizing HI-13 tandem accelerator irradiation terminal at CIAE,the two new zirconium alloy cladding pipe samples were irradiated for 5 dpa by 100 MeV Fe ions at 300℃.Before and after irradiation,positron annihilation lifetime spectra were measured.The results show that both of the annihilation lifetime of two samples before irradiation are the lifetime of positron trapped in mono-vacancy of Zr metal,which implies that defects have not been eliminated by the final annealing with insufficient temperature and time.The positron annihilation lifetime of two post-irradiation samples decreases.Because of the redistribution of Fe induced by irradiation and the segregation of Fe atoms at the interfacial region between hcpα-Zr matrix and bccβ-Nb second phase particle,the positron is more easily trapped into the phase boundary with open space and annihilated with electrons of Fe atoms.