国产RPV钢铁离子辐照脆化行为的正电子湮灭研究

Positron Annihilation Investigation of Embrittlement Behavior in Chinese RPV Steels after Fe-Ion Irradiation

选取服役于我国高温气冷示范电站的反应堆压力容器(reactor pressure vessel,RPV)钢A508-3和纯Fe,采用3 Me V铁离子进行高温(250℃)与室温(约25℃)辐照,辐照损伤分别达0.1、0.5和1.0 dpa,对样品分别进行正电子湮灭和纳米压痕硬度研究。结果表明,辐照会使材料内部产生缺陷,这种缺陷以空位型缺陷和溶质原子团簇缺陷为主。且高温辐照产生的缺陷密度低于室温辐照,其中高温的退火效应使材料内部缺陷发生一定程度的回复。辐照后RPV钢和纯Fe都产生了一定程度的硬化,硬化程度随辐照损伤的增加而增高。对于RPV钢,高温辐照比室温辐照使材料内部产生更少的空位型缺陷和更多的溶质原子团簇型缺陷,因而RPV钢的辐照硬化可能主要是由溶质原子团簇型缺陷引起的。

The reactor pressure vessel（RPV） is the key component in the nuclear power plant, which is considered irreplaceable and can be the life-limiting feature of the operation of nuclear power plant if its mechanical properties degrade sufficiently. High temperature gas-cooled reactor（HTGR） has perfect inherent safety, which is intended to be one of the fourth generation advanced nuclear reactors. However,HTGR has different service temperature with pressurized water reactor（PWR）, that the service temperature of HTGR is 250 ℃ and that of PWR is 290 ℃. So the irradiation behaviour of RPV in HTGR is expected to be investigated. In this wok, 3 Me V Fe-ion irradiation was performed on Chinese A508-3 reactor pressure vessel steel which is employed by high-temperature gas-cooled reactors and pure Fe under room temperature（about 25 ℃） and high temperature（250 ℃）. The ion doses were 0.1, 0.5 and 1.0 dpa for both room temperature irradiation and high temperature irradiation. SRIM modeling was performed before irradiation experiments to guide the experimental details. Positron annihilation Doppler broadening（PADB） spectroscopy experiments and nano-indentation tests（to study embrittlement behavior） were conducted for characterization. It is found that after both room temperature irradiation and high temperature irradiation, the densities of defects in the reactor pressure vessel steel and pure Fe increase, and the type of defects could be vacancy-type and solute cluster type from PADB results. The vacancy-type defect density under high temperature irradiation is lower than that under room temperature irradiation.That is because high temperature can recover the defects formed during irradiation. The hardness test results show that for both the reactor pressure vessel steel and pure Fe, the irradiation hardening increases with increasing dose. Compared to room temperature irradiation, high temperature irradiation can produce more solute clusters and fewer vacancy-type defects in the reactor pressure vessel steel.So the irradiation hardening of the reactor pressure vessel steel might be caused mainly by the formation of solute clusters.