Corrosion behavior of high-level waste container materials Ti and Ti–Pd alloy under long-term gamma irradiation in Beishan groundwater* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51471160, 11775102, and 11965001) and the Fundamental Research Funds for the Central Universities, China (Lanzhou University, Grant No. lzujbky-2018-19).

Abstract

Titanium and titanium–palladium alloys are important potential materials for nuclear waste container, which will endure both intense γ-irradiation and groundwater erosion. Therefore, it is very important to investigate the corrosion behavior of the container materials. In this research, the cumulative dose effect of TA8-1 type titanium–palladium alloy (TA8-1) and TA2-type pure titanium (TA2) under γ-irradiation was studied based on the geological disposal of nuclear wastes. The irradiation experiments were performed at room temperature using 60Co gamma sources with a 5.0-kGy⋅h−1 intensity for 40, 80 or 160 days, respectively. The pH value and conductivity of Beishan groundwater were investigated. The results showed that the pH value changed from alkaline (8.22) to acidic (2.46 for TA8-1 and 2.44 for TA2), while the un-irradiated solution remained alkaline (8.17 for TA8-1 and 8.20 for TA2) after 160 days. With the increase of irradiation dose, the conductivity increases rapidly and then tends to become stable, which indicates that the titanium dioxide corrosion layer formed on the surface of the sample surface effectively prevents further corrosion. Meanwhile, XRD and SEM–EDS analysis results show that the main components of corrosion products are TiO2 and TiO. The titanium on the surface of the sample is oxidized, resulting in slight uneven local corrosion. The results show that TA8-1 and TA2 are suitable to be used as candidate materials for high-level waste (HLW) disposal containers due to their excellent performance under long-term and high-dose irradiation corrosion.