权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

AMS-UK: A UK Accelerator Mass Spectrometry Facility for Nuclear Fission Research

AMS-UK：英国用于核裂变研究的加速器质谱设施

基本信息

批准号：
EP/T01136X/1
负责人：
Malcolm Joyce
金额：
$ 355.57万
依托单位：
Lancaster University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FT01136X%2F1
关键词：
AMS UK Accelerator Mass Spectrometry

项目摘要

Phase 2 of the National Nuclear User Facility is a significant investment in science and engineering facilities and apparatus to support nuclear fission research on radioactive samples in the UK. This proposal is submitted under this initiative and concerns a very sensitive technique for the assessment of a significant group of radioactive elements produced in nuclear reactors: the actinides. The actinides are amongst the heaviest known elements, formed as a result of neutron capture on uranium. They are all radioactive, to a greater or lesser degree, and several are very long-lived. The combination of their radioactivity and chemistry renders some significant radio toxins that have be managed and stored carefully. The most significant is plutonium, which is often present in the form of the isotope 239Pu and to a lesser extent, 238Pu, 240Pu, 241Pu, 242Pu and occasionally 244Pu.Plutonium is effectively extinct on Earth as a natural product of the Big Bang because its half life is too short to have survived. However, minuscule quantities are known to have formed in geological deposits that are naturally rich in uranium, via natural neutron capture processes on the most abundant uranium isotope, 238U, in these ores. Plutonium has been re-introduced to the environment, predominantly as a result of atmospheric nuclear weapons testing in the 1950-1990 period (fallout), but also as a result of nuclear reactor accidents (Chernobyl and Fukushima) and the dispersion of effluents from nuclear reprocessing activities: in the UK this is thought to be most significant due to activities at Sellafield and Dounreay.The high radio-toxicity of plutonium requires that materials contaminated by it are managed and stored very carefully, especially since large quantities are soils from contaminated land and building materials from contaminated structures. However, how do we discern what was there before, often in a wider context (from fallout and natural arisings in uranium-rich ores), from what has been dispersed locally? Simply 'detecting' plutonium is not sufficient because, whilst radioactive, it is usually dispersed at such minuscule levels there is not enough to provide enough radiation to detect it on a practical basis. Special samples can be made and the alpha radioactivity counted from these, but this does not allow individual isotopes to be discerned, which is an important requirement: fallout material is often rich in the heavier isotopes (242Pu and 244Pu) whereas material from nuclear reactors tends to be rich in 239Pu, 240Pu and 241Pu.In this proposal, we recommend investing in a recently-established capability to measure plutonium isotopes by their mass rather than their radioactivity. The isotopes are accelerated from a sample into which the plutonium has been extracted by dissolution, and dispersed in a magnetic field. They are ionised and collected in a particle detector where their position (as a result of the magnetic field deflection) and their rate of energy deposition are used to identify them, usually as a ratio of the rare isotope to an abundant alternative, where the latter can be introduced artificially to highlight the rare variant. This approach is called accelerator mass spectrometry. Until recently, this relied on large machines at particle accelerator facilities and was very expensive. Now, commercial systems are available that are smaller and cheaper, but the UK does not have one despite being the custodian of the largest stockpile of civil-separated plutonium. This proposal recommends that one of these is installed at Lancaster University, for external usage by the whole nuclear fission community. This is an important proposal because the UK Government committed to an agreement, the 'nuclear sector deal', which requires that businesses reduce the cost of decommissioning by at least 20%. Improved plutonium assay of contaminated materials will make a significant contribution to this aim.

国家核用户设施的第二阶段是对科学和工程设施和仪器的重大投资，以支持联合王国对放射性样品的核裂变研究。这项建议是在这一倡议下提出的，涉及一种非常敏感的技术，用于评估核反应堆产生的一组重要的放射性元素：锕系元素。锕系元素是已知最重的元素之一，是由铀俘获中子形成的。它们都具有或多或少的放射性，其中一些寿命很长。它们的放射性和化学性质的结合使一些重要的放射性毒素得到了仔细的管理和储存。最重要的是钚，它通常以同位素239 Pu的形式存在，在较小程度上，238 Pu，240 Pu，241 Pu，242 Pu和偶尔的244 Pu。然而，已知在天然富含铀的地质矿床中，通过对这些矿石中最丰富的铀同位素238 U的天然中子捕获过程，形成了微量的铀。钚重新进入环境，主要是由于1950-1990年期间的大气层核武器试验（沉降物），但也由于核反应堆事故（切尔诺贝利和福岛）和核后处理活动流出物的扩散：在英国，由于塞拉菲尔德和敦雷的活动，这被认为是最重要的。钚的毒性要求对受其污染的材料进行非常仔细的管理和储存，特别是因为大量材料是来自受污染土地的土壤和来自受污染结构的建筑材料。然而，我们如何辨别以前存在的东西，通常是在更广泛的背景下（来自富铀矿石中的沉降物和自然沉积物），从分散在当地的东西中？简单地“检测”钚是不够的，因为虽然具有放射性，但它通常分散在如此微小的水平上，不足以提供足够的辐射来实际检测它。可以制作特殊的样品，并从这些样品中计算α放射性，但这不允许识别单个同位素，这是一个重要的要求：沉降物通常富含重同位素（242 Pu和244 Pu），而来自核反应堆的材料往往富含239 Pu，240 Pu和241 Pu。我们建议投资于最近建立的通过质量而不是放射性来测量钚同位素的能力。同位素从样品中加速，钚已经通过溶解提取到样品中，并在磁场中分散。它们被电离并收集在粒子探测器中，在那里它们的位置（由于磁场偏转）和它们的能量沉积速率被用来识别它们，通常是稀有同位素与丰富替代物的比率，后者可以人为地引入以突出稀有变体。这种方法被称为加速器质谱法。直到最近，这依赖于粒子加速器设施中的大型机器，并且非常昂贵。现在，已经有了更小、更便宜的商业系统，但英国没有，尽管它是最大的民用分离钚储备的保管者。该提案建议在兰开斯特大学安装其中一个，供整个核裂变团体外部使用。这是一项重要的提议，因为英国政府承诺达成一项协议，即“核部门协议”，要求企业将退役成本降低至少20%。改进污染材料的钚检验将大大有助于实现这一目标。