Abstract:

The development and use of nuclear energy has generated a substantial amount of high-level radioactive nuclear wastes (HLWs), which are characterized by strong radioactivity, high toxicity, high heat generation and long half-life. These characteristics make it difficult to effectively manage HLWs using traditional physical, chemical or biological methods. Deep geological disposal is generally considered to be the most feasible option for disposal of HLWs, with the key scientific challenge being the in-depth study of the radionuclide migration behaviour in groundwater. In recent years, numerical simulation technology has become deeply integrated with disposal efforts. Significant progress has been made in application of computer-driven numerical simulations to study nuclide migration in HLWs disposal. This study reviews the mechanisms and processes of nuclide migration in disposal of HLWs based on an extensive literature review, summarizes the influencing factors and the research experiences in this field, and discusses future research directions. The research results suggest that the scale of the study area and the degree of fracture development should be comprehensively considered when selecting an appropriate model, and that the speciation and properties of nuclides are the key determinants of migration behaviour, while factors such as rock fissure networks, colloidal presence, and groundwater compositions significantly affect the migration paths and rates. Despite notable progress, numerical simulations face significant challenges in practical applications. These challenges include accurately simulating multi-scale and multiphase flows, and addressing complex geological structures and heterogeneous materials. Additionally, model validation and uncertainty analysis remain pressing issues. Future research should focus on optimizing numerical models, improving simulation accuracy, and promoting interdisciplinary studies to better address the complexity and uncertainty inherent in radionuclide migration during HLWs disposal.

Key words: high-level radioactive wastes (HLWs), deep geological disposal, numerical simulation, radionuclide migration, safety evaluation, groundwater environment

摘要：

核能的开发与利用产生大量高放废物，这些废物具有强放射性、高毒性、热量显著并且半衰期长，很难用传统的物理、化学、生物手段有效去除。目前，深地质处置被广泛认为是高放废物最有效的处理方案，其安全评估的关键在于深入研究放射性核素在地下水中的迁移行为。近年来，数值模拟技术与高放废物处置不断深入结合，以计算机驱动的数值模拟在高放废物处置核素迁移领域取得了巨大进展。本研究通过广泛的文献调研，介绍了高放废物处置中核素迁移的机制与过程，回顾了该领域的数值模拟研究经验，并归纳总结了核素迁移的影响因素，同时对未来高放废物地质处置中核素迁移研究的发展方向提出了展望。研究结果表明，核素迁移模型的选择应综合考虑研究区域的规模和裂隙发育程度；核素的形态与性质是决定核素迁移行为的关键因素，而岩石裂隙网络、胶体存在、地下水成分等因素会显著影响核素的迁移路径和速率。尽管取得了显著进展，数值模拟在实际应用中仍面临诸多挑战，如精确模拟多尺度、多相流动，处理复杂地质结构和异质性材料等。此外，模型验证和不确定性分析也是亟待解决的重要问题。未来研究应着力优化数值模型，提高模拟精度，推动多学科交叉研究，以更好地应对高放废物处置中核素迁移的复杂性和不确定性。

关键词: 高放废物, 深地质处置, 数值模拟, 放射性核素迁移, 安全评价, 地下水环境