Chen Ying, Sun Yandong, Bai Yang, Zhao Ziqian, Wei Zheng, Liu Fang, Yuan Zhongwei, Yan Taihong, Zheng Weifang
China Institute of Atomic Energy, Beijing 102413, China.
Materials (Basel). 2024 Nov 25;17(23):5771. doi: 10.3390/ma17235771.
M5 cladding has emerged as a prominent fuel cladding material due to its excellent corrosion resistance. The dissolution behavior of M5 cladding is critical in both the initial cleaning stage and the reprocessing of spent fuel cladding. This study investigated the dissolution of M5 cladding in hydrofluoric-nitric (HF-HNO) mixed acid at varying concentrations. When the HF concentration exceeds 0.5 mol/L, the addition of strong oxidizing HNO significantly reduces the dissolution rate. Moreover, HNO effectively inhibits the HF-induced corrosion pitting, lowering surface roughness to 0.812 μm at a 1:5 ratio of HF:HNO. In addition, a surface structural analysis reveals the dissolution mechanism of M5 cladding. The β-Nb precipitated in the mixed acid was oxidized to stable NbO by HNO while the M5 matrix surface was continuously oxidized to ZrO. This passivation layer inhibits further dissolution, slowing the process and enhancing the uniformity of M5 cladding.
M5包壳因其出色的耐腐蚀性而成为一种重要的燃料包壳材料。M5包壳的溶解行为在乏燃料包壳的初始清洗阶段和后处理过程中都至关重要。本研究调查了M5包壳在不同浓度的氢氟酸 - 硝酸（HF - HNO）混合酸中的溶解情况。当HF浓度超过0.5 mol/L时，添加强氧化性的HNO会显著降低溶解速率。此外，HNO能有效抑制HF引发的腐蚀点蚀，在HF:HNO比例为1:5时，将表面粗糙度降低至0.812μm。另外，表面结构分析揭示了M5包壳的溶解机制。在混合酸中析出的β - Nb被HNO氧化为稳定的NbO，而M5基体表面则不断被氧化为ZrO。这一钝化层抑制了进一步溶解，减缓了溶解过程并提高了M5包壳的均匀性。
