Effect of neutron and ion irradiation on the metal matrix and oxide corrosion layer on Zr-1.0Nb cladding alloys
Effect of neutron and ion irradiation on the metal matrix and oxide corrosion layer on Zr-1.0Nb cladding alloys
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DOI：
10.1016/j.actamat.2019.04.055
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发表时间：
2019-07-01
期刊：
影响因子：
9.4
通讯作者：
Grovenor, Chris
中科院分区：
文献类型：
--
作者：
Hu, Jing;Garner, Alistair;Grovenor, Chris
本文对再结晶Zr-1.0Nb合金在不同条件下的腐蚀和辐照进行了详细的研究。经过540天的反应堆运行和约5 dpa的损伤，中子辐照样品没有显示出严重的辐射增强腐蚀迹象，仍然处于预过渡阶段。中子辐照Zr-1.0Nb的良好耐腐蚀性可与氧化物中较高的四方相体积分数和较少的互连纳米孔隙/裂纹有关。这表明较少的四斜晶系到单斜晶系的转变，导致中子辐照样品中更多的保护性氧化物，几乎没有证据表明氧气或水向金属氧化物界面渗透的短路路径。在具有缓慢的总体氧化速率的样品上的这些观察结果与互连孔隙率可导致早期转变和快速氧化的假设一致。四氧化二铌可以通过辐射稳定化，或者通过从SPP中局部释放杂质物质来稳定化，例如从Zr-Nb-Fe沉淀物或辐射引入的沉淀物（Rips）中溶解Fe，所述沉淀物可能是小的β-Nb簇。在高压釜样品中，氧化物由排列良好的柱状等轴显微组织组成，而在中子辐照样品中观察到更复杂的氧化物晶粒结构。随着氧化物继续生长，在金属基质中存在更多的环状物、溶解的Fe和RIP，然而，腐蚀速率足够低以使四氧化二锆稳定，并且存在低价氧化物+ Zr（Osat）相以起到保护作用，因此在辐射后没有增强的腐蚀。原位离子辐照在TEM中没有发现可见的缺陷簇或空隙的氧化物，这表明辐射损伤的金属基体，而不是氧化物可能有更强的影响后，中子辐照的腐蚀机制，但是，级联损伤是不可见的，在这种情况下。中子辐照似乎对促进β-Nb沉淀物在辐照期间快速氧化或溶解到周围氧化物或金属中也几乎没有影响。根据目前核燃料包壳合金的腐蚀机制，对这些结果进行了讨论。由Elsevier Ltd代表Acta Materialia Inc.出版。
A detailed study has been carried out on recrystallised Zr-1.0Nb alloys corroded and irradiated under different conditions, including ex-autoclave and ex-reactor samples. After 540 days in reactor and damage around 5 dpa, the neutron irradiated sample shows no serious evidence for radiation enhanced corrosion and is still in pre-transition stage. The good corrosion resistance of the neutron irradiated Zr-1.0Nb can be related to the higher volume fraction of tetragonal phase and fewer interconnected nano porosity/cracks in the oxide. This indicates less tetragonal to monoclinic transition, leads to more protective oxide in the neutron irradiated sample, containing little evidence for short circuit paths for the penetration of oxygen or water towards the metal-oxide interface. These observations on a sample with a slow overall oxidation rate are consistent with the hypothesis that interconnected porosity can lead to early transitions and rapid oxidation. Tetragonal oxide can be either stabilised by irradiation, or stabilised by local release of impurity species from SPPs such as dissolution of Fe from Zr-Nb-Fe precipitates or radiation introduced precipitates (Rips) which is likely to be small beta-Nb clusters. The oxide consists of well-aligned columnar-equiaxed microstructure in the autoclave sample while a more complex oxide grain structure was observed in the neutron-irradiated sample. As oxide continues to grow, there are more and loops, dissolved Fe and RIPs in the metal matrix, however, the corrosion rate is low enough for the tetragonal oxide to stabilise and suboxide + Zr(Osat) phases exist for protectiveness, so there is no enhanced corrosion after radiation. In situ ion irradiation in the TEM revealed no visible defect clusters or voids in the oxide, suggesting that radiation damage to the metal matrix rather than oxide may have a stronger effect on corrosion mechanisms after neutron irradiation, however, cascade damages are not visible in this case. Neutron irradiation also seems to have little effect on promoting fast oxidation or dissolution of beta-Nb precipitates into the surrounding oxide or metal during irradiation. These results are discussed in the light of the current mechanisms for corrosion of nuclear fuel cladding alloys. Published by Elsevier Ltd on behalf of Acta Materialia Inc.