Effect of sediment and groundwater flow heterogeneity on accurately modelling radionuclide transport at UK nuclear sites

英国核退役管理局受权监督英国约20个核设施的建筑物和放射性废物的清除。其目的是以安全和具有成本效益的方式提供英国民用核遗产的退役和清理，并在可能的情况下加速减少危害的工作计划。NDA并不直接管理英国的核设施。它通过与专门设计的公司签订合同来监督这项工作，这些公司被称为工地许可证公司。NDA决定了退役管理的总体战略和优先事项。其年度预算为32亿英镑。NDA预算的绝大部分是通过与现场许可公司的合同支出的，这些公司还将合同分包给提供特殊服务的其他公司。塞拉菲尔德核电站位于英格兰坎布里亚郡海岸，是一个大型核燃料后处理、核废料储存、核退役和前核能发电基地。该基地占地两平方英里，包括200多个核设施和1000多座建筑。它是欧洲最大的核设施，也是世界上在同一地点拥有最多样化核设施的地方。它将于2120年完全退役，耗资1210亿英镑。包括塞拉菲尔德在内的许多英国核电站都位于沿海平原上，并被厚厚的河流冰川冲积层所覆盖。这些沉积物在性质上是高度不均匀的，由粘土大小到鹅卵石大小的材料组成。沉积物结构也经常有相当大的横向变异性，反映了它们形成过程中沉积环境的变化。历史上曾发生过几次未经许可的放射性核素和/或含碳氢化合物液体泄漏事件。其中含有放射性核素，如Tc-99和H-3，它们在地下水中高度流动，其他如Sr-90、C-137和U，它们显示出吸附控制的运输。其他化学污染物，如非水相液体中的碳氢化合物及其溶解产物，也被意外地释放到地下水中。在塞拉菲尔德，有200多个地下水监测钻孔，在那里记录了含水层物质和地下水数据。这为在一个非常复杂的松散含水层结构中存在广泛的放射性和化学污染羽流提供了证据，这些羽流与特定废物类型和过程随时间的不同释放有关。历史上曾发生过几次未经许可的放射性核素和/或含碳氢化合物液体泄漏事件。其中含有放射性核素，如Tc-99和H-3，它们在地下水中高度流动，其他如Sr-90、C-137和U，它们显示出吸附控制的运输。其他化学污染物，如非水相液体中的碳氢化合物及其溶解产物，也被意外地释放到地下水中。在塞拉菲尔德，有200多个地下水监测钻孔，在那里记录了含水层物质和地下水数据。这为在一个非常复杂的松散含水层结构中存在广泛的放射性和化学污染羽流提供了证据，这些羽流与特定废物类型和过程随时间的不同释放有关。该项目符合英国研究委员会EPSRC -核裂变研究领域的研究范围。该研究领域包括废物管理、场址退役、环境监管以及公众对英国核场址现有运营的接受程度。这一研究领域的战略重点旨在通过促进制定在现有核场址执行安全、成本效益高的清理和废物处理的办法，解决当前核方案面临的退役挑战。

The UK Nuclear Decommissioning Authority is mandated to oversee the removal of buildings and radioactive wastes present at ~20 UK nuclear sites. Its purpose is to deliver the decommissioning and clean-up of the UK's civil nuclear legacy in a safe and cost-effective manner, and where possible to accelerate programmes of work that reduce hazard. The NDA does not directly manage the UK's nuclear sites. It oversees the work through contracts with specially designed companies known as Site Licence Companies. The NDA determines the overall strategy and priorities for managing decommissioning. Its annual budget is £3.2 billion. The vast majority of the NDA budget is spent through contracts with Site Licence Companies, who also sub contract to other companies which provide special services. The Sellafield site is a large nuclear fuel reprocessing, nuclear waste storage, nuclear decommissioning and former nuclear power generating site on the coast of Cumbria, England. The site covers an area of two square miles and comprises more than 200 nuclear facilities and more than 1,000 buildings. It is Europe's largest nuclear site and has the most diverse range of nuclear facilities in the world situated on a single site. It is due to be fully decommissioned by 2120 at a cost of £121bn. Many UK nuclear sites, including Sellafield, are located on coastal plains and are underlain by thick fluvial-glacial alluvium deposits. These sediments are highly heterogeneous in nature and consist of layers ranging from clay size right up to cobble sized materials. There is also often considerable lateral variability in sediment texture reflecting changing depositional environments present during their formation. Historically there has been several events where unauthorised releases of radionuclide and/ or hydrocarbon containing fluids have occurred. These have contained radionuclides such as Tc-99 and H-3 that are highly mobile in groundwater, others such as Sr-90, C-137 and U which display sorption controlled transport. Other chemical contaminants, such as hydrocarbons as Non-Aqueous Phase Liquids and their resulting dissolution products, have also been accidentally released into groundwater. At Sellafield, over 200 groundwater monitoring boreholes exist, where aquifer materials and groundwater data has been recorded. This has provided evidence for the existence of extensive radioactive and chemical contamination plumes in a very complex unconsolidated aquifer structure relating to different releases from specific waste types and processes over time. Historically there has been several events where unauthorised releases of radionuclide and/ or hydrocarbon containing fluids have occurred. These have contained radionuclides such as Tc-99 and H-3 that are highly mobile in groundwater, others such as Sr-90, C-137 and U which display sorption controlled transport. Other chemical contaminants, such as hydrocarbons as Non-Aqueous Phase Liquids and their resulting dissolution products, have also been accidentally released into groundwater. At Sellafield, over 200 groundwater monitoring boreholes exist, where aquifer materials and groundwater data has been recorded. This has provided evidence for the existence of extensive radioactive and chemical contamination plumes in a very complex unconsolidated aquifer structure relating to different releases from specific waste types and processes over time. This project fits within UK research council areas of research within the EPSRC - Nuclear Fission research area. This research area includes waste management, site decommissioning, environmental regulation, and the public acceptability of existing operations at UK nuclear sites. The strategic focus of this research area aims to address the decommissioning challenges faced by current nuclear programmes by facilitating the development of approaches for implementing safe, cost-effective clean-up and waste disposal at existing nuclear sites.