In situ TEM study of heavy-ion irradiation-induced amorphisation and electron beam-induced recrystallisation in powellite (CaMoO4)
In situ TEM study of heavy-ion irradiation-induced amorphisation and electron beam-induced recrystallisation in powellite (CaMoO4)
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DOI：
10.1016/j.actamat.2023.119391
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发表时间：
2023-10
期刊：
影响因子：
9.4
通讯作者：
Tamás Zagyva;A. H. Mir;L. Leay;Brian O'Driscoll;Mike Harrison;Tracey Taylor;Robert W. Harrison
中科院分区：
文献类型：
--
作者：
Tamás Zagyva;A. H. Mir;L. Leay;Brian O'Driscoll;Mike Harrison;Tracey Taylor;Robert W. Harrison
英国富含钼的放射性废流将被玻璃化成含有碳酸钙(CaMoO4)晶体的玻璃复合高放废物(HLW)产品。这些材料将在地质处置设施中暴露在自我照射下数千年。我们的重离子和电子辐照结果，加上对以前研究的全面回顾，揭示了关于POWELITE辐射耐受性的新细节。在本研究中，在-160~-80℃温度范围内，用500keV Ar2+和600keV Xe2+离子辐照了POWELITE晶体，并用透射电子显微镜对其进行了原位分析。在低温下(-160℃到-105℃之间)，Xe辐照的临界非晶化剂量(DC)较高，这很可能是由于级联堆芯中显著的缺陷恢复所致。在-105℃以上，Ar辐照的DCIS较高。随着温度的升高，辐照缺陷的动态退火变得更加有效；我们的结果表明，与Xe辐照产生的级联缺陷相比，Ar辐照形成的点缺陷更容易受到动态退火的影响。我们还首次提出了300keV电子束在非晶态POWELITE中诱导再结晶的证据，用大范围的电子通量(0.6-5.2KEV×1016e/cm~2/S)研究了非晶态POWELITE从室温到低温的响应。与以前的研究不同，我们的新数据表明，POWELITE很容易被α反冲核非晶化，而β辐照可能会导致缺陷复合。
Molybdenum-rich radioactive waste streams in the UK will be vitrified into glass composite high-level waste (HLW) products containing powellite (CaMoO4) crystals. These materials will be exposed to self-irradiation in a geological disposal facility for thousands of years. Our heavy-ion and electron irradiation results, together with a comprehensive review of previous studies, reveal new details on the radiation tolerance of powellite. In this study, powellite crystals were exposed to 500 keV Ar2+and 600 keV Xe2+ion irradiations between -160 and -80 °C and were analysed in situ via transmission electron microscopy (TEM). At low temperatures (between -160 and -105 °C), the critical amorphisation dose (Dc) is higher for the Xe irradiation, most likely due to the significant defect recovery in the cascade core. Above -105 °C, the Dcis higher for the Ar irradiation. The dynamic annealing of radiation-induced defects becomes more efficient as the temperature increases; our results suggest that point defects formed during Ar irradiation are more susceptible to dynamic annealing compared with defects in the cascades generated during Xe irradiation. We also present the first evidence of 300 keV electron beam-induced recrystallisation in amorphous powellite by studying its response from room temperature to cryogenic temperatures inside the TEM using a wide range of electron fluxes (0.6–5.2 × 1016e/cm2/s). In contrast to previous research, our new data suggest that powellite is susceptible to amorphisation by alpha recoil nuclei, and that beta irradiation may cause defect recombination.