Understanding Radioactive 'Hot' Particle Evolution in the Environment

虽然放射性一直存在于环境中，但在过去70年中，核材料的工业和军事用途导致了许多故意和意外的放射性材料释放。这些物质对人类和更广泛的生态系统的影响取决于放射性核素在环境中的行为。放射性“热”粒子往往是向环境释放的重要组成部分，因此，它们通常出现在核场址（如塞拉菲尔德）或受故意释放影响的地区（如联合王国的Ravenglass和Eskmeals）或事故（如切尔诺贝利和福岛）。与粒子结合的放射性核素在释放后，与均匀分散的污染物相比，在环境中的表现非常不同。然而，对热粒子中放射性核素的组成和化学形式，或控制其长期稳定性、归宿和影响的过程，特别是在分子尺度上，显然缺乏了解。这在我们的放射性核素环境行为的概念模型中留下了巨大的空白，使得很难促进对放射性核素迁移和归宿进行可靠的长期预测。最后，这些不确定性的影响是深远的：对我们预测放射性核素在环境中的行为的能力缺乏信心，影响了公众对优先问题的看法，例如，核废料的地质处置和新核建设的实施。因此，更好地量化和理解热粒子在环境中的短期到长期行为和潜在影响至关重要。考虑到上述情况，我们将使用一系列实验室实验和现场样本，结合最先进的表征工具，对环境中热粒子在几个月到几十年的时间尺度上的演变有一个清晰的理解。由于富铀热粒子在环境中的普遍存在，我们的大部分实验工作将集中在富铀热粒子上，我们将在流动柱中的一系列环境条件下改变这些粒子，为期> 1年。在整个过程中，我们将监测溶液化学的变化;此外，我们将使用一系列同步加速器、质谱和电子显微镜技术来评估颗粒结构、化学和同位素组成随时间的变化，以及表征任何形成的特征。第二相。补充我们的柱实验，并在努力了解更长的时间尺度的反应（数年至数十年），并评估更广泛的颗粒类型的过程，我们将使用同样的技术从受污染的现场样本中分离颗粒物，（例如，从塞拉菲尔德地区和埃斯克梅莱斯射击场）。这项工作的信息将导致一个非常-当环境中存在热粒子时放射性核素行为的改进概念模型。此外，通过与一系列关键利益相关者（例如EA，DSTL）合作，我们可以利用这些知识更好地预测污染场地的辐射风险，并为土地管理/监测实践提供信息。

Whilst radioactivity has always been present in the environment, industrial and military use of nuclear materials over the past 70 years has led to numerous deliberate and accidental releases of radioactive materials. The impact of these materials on humans and wider ecosystems is controlled by the behaviour of the radionuclides in the environment. In turn, radionuclide behaviour and resultant bioavailability is dictated by their concentration and chemical form.Radioactive 'hot' particles are often an important part of releases to the environment and thus they are commonly found at nuclear sites (e.g. Sellafield) or in areas impacted by deliberate releases (e.g. Ravenglass and Eskmeals, UK) or accidents (e.g. Chernobyl and Fukushima). After release, particle-bound radionuclides have been shown to behave very differently in the environment when compared with homogeneously dispersed contamination. However, there is a distinct lack of knowledge about the composition of, and chemical form of radionuclides in hot particles, or of the processes that control their longer-term stability, fate and impact, particularly at the molecular scale. This leaves significant gaps in our conceptual models of radionuclide environmental behaviour, making it difficult to facilitate robust, long-term predictions of radionuclide transport and fate. Ultimately, the impact of these uncertainties is profound: a lack of confidence in our ability to predict radionuclide behaviour in the environment impacts on the public perception of priority issues, for example, the geological disposal of nuclear waste and the implementation of new nuclear build. As a result, better quantification and understanding of the short- to long-term behaviour and potential impacts of hot particles in the environment is crucial.Reflecting the above, we will use a range of laboratory experiments and field samples combined with state-of-the-art characterisation tools, to develop a clear understanding of hot particle evolution in the environment over timescales ranging from months to decades. The majority of our experimental work will focus on uranium-rich hot particles due to their prevalence in the environment, and we will alter these under a range of environmental conditions in flowing columns, for periods of > 1 year. Throughout, we will monitor changes in solution chemistry; further, we will use a range of synchrotron, mass spectrometry, and electron microscopy techniques to assess changes over time in particle structure, chemistry, and isotopic composition, as well as characterising the formation of any secondary phases. Complementary to our column experiments, and in an effort to understand longer timescale reactions (years to decades) and assess processes across a wider range of particle types, we will use the same techniques to characterise particles from contaminated field samples (e.g. from the Sellafield area and Eskmeals firing range).The information from this work will lead to a much-improved conceptual model of radionuclide behaviour when hot particles are present in the environment. Further, by working with a range of key stakeholders (e.g. EA, DSTL), we can use this knowledge to predict radiological risk at contaminated sites better and inform land management / monitoring practices.