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2M、3O和4M型钙钛锆石固化体的α粒子辐照行为研究

The Irradiation Behavior of 2M, 3O and 4M Polytypes Zirconolite Solid Solutions Under α Particles

  • 摘要: 高放废物固化体的长期辐照稳定性是评价其深地质处置安全性的关键指标之一。本工作利用500 keV He2+离子束辐照2M、3O和4M型钙钛锆石陶瓷固化体,研究高放核素长期α衰变辐照对陶瓷结构的损伤行为。三种钙钛锆石样品通过传统高温固相法(1400 °C,48 h两次烧结)合成。掠入射X射线衍射(GIXRD)、Raman光谱和XPS研究结果发现,在α粒子辐照下,zirconolite-2M固化体在辐照诱导非晶化的过程中经历了zirconolite-2M到zirconolite-4M,再到pyrochlore的结构演变;zirconolite-3O在5×1015 ions/cm2剂量下部分晶体结构转变为钙钛矿,在1×1016 ions/cm2以上剂量快速转变为无序烧绿石;zirconolite-4M样品在1×1017 ions/cm2剂量时依旧保留zirconolite-4M主相,次生无序烧绿石/缺陷萤石晶相。综上,从维持晶体结构稳定性来看,zirconolite-2M和zirconolite-3O的抗α粒子辐照能力相似,略弱于zirconolite-4M固化体。

     

    Abstract: The long-term irradiation stability of high-level radioactive waste forms is one key indicators for the safety evaluation of deep geological disposal. In this work, 500 keV He2+ ion beams irradiation of zirconolite-2M, zirconolite-3O and zirconolite-4M three-type solid solutions were performed to study the structure damage behavior from long-term α decay irradiation. All samples were synthesized through conventional high-temperature solid-state reaction (sintering at 1400 °C for 48 h twice). The grazing incidence x-ray diffraction (GIXRD), Raman and X-ray photoelectron spectroscopy (XPS) results indicated that zirconlite-2M sample experienced crystalline phase evolution from zirconolite-2M to zirconolite-4M, and then to pyrochlore during the amorphization process by α particles irradiation. zirconolite-3O phase partially transformed to perovskite at 5×1015 ions/cm2 dose, and perovskite quickly transformed to disordered pyrochlore at dose above 1×1016 ions/cm2. Zirconolite-4M sample still retained the main phase of zirconolite-4M at a dose of 1×1017 ions/cm2, with secondary disordered pyrochlore or defect fluorite phase. In summary, the irradiation damage resistance of zirconolite-2M and zirconolite-3O was similar, and slightly lower than that of zirconolite-4M from the perspective of maintaining crystal structure stability.

     

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