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.

国家核用户设施第二阶段是对科学和工程设施和设备的重大投资，以支持英国放射性样品的核裂变研究。该提案是根据该倡议提交的，涉及一种非常敏感的技术，用于评估核反应堆中产生的一组重要放射性元素：锕系元素。锕系元素是已知最重的元素之一，是由铀捕获中子而形成的。它们都或多或少地具有放射性，其中有一些寿命非常长。它们的放射性和化学性质相结合，产生了一些重要的放射性毒素，需要仔细管理和储存。最重要的是钚，它通常以同位素 239Pu 的形式存在，其次是 238Pu、240Pu、241Pu、242Pu，偶尔还有 244Pu。钚作为大爆炸的自然产物，在地球上实际上已经灭绝了，因为它的半衰期太短，无法生存。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 238U 的自然中子捕获过程，形成了极少量的铀。钚已被重新引入环境，主要是由于 1950-1990 年期间的大气核武器试验（放射性尘埃），但也是由于核反应堆事故（切尔诺贝利和福岛）以及核反应堆流出物的扩散造成的。后处理活动：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。钚的高放射性毒性要求对其污染的材料进行管理和处理储存非常小心，特别是因为大量是来自受污染土地的土壤和来自受污染建筑物的建筑材料。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（来自富铀矿石的沉降物和自然生成物），与当地分散的东西？仅仅“检测”钚是不够的，因为虽然具有放射性，但它通常以极小的水平分散，不足以提供足够的辐射来在实际基础上检测它。可以制作特殊样品并从中计算 α 放射性，但这不允许辨别单个同位素，这是一个重要的要求：沉降物材料通常富含较重的同位素（242Pu 和 244Pu），而来自核反应堆的材料往往富含较重的同位素（242Pu 和 244Pu）。富含 239Pu、240Pu 和 241Pu。在本提案中，我们建议投资于最近建立的测量钚的能力同位素通过质量而不是放射性来确定。通过溶解提取钚的样品中的同位素被加速，并分散在磁场中。它们被电离并收集在粒子探测器中，其中它们的位置（由于磁场偏转）和能量沉积速率用于识别它们，通常作为稀有同位素与丰富替代品的比率，其中后者可以人为地引入以突出罕见的变体。这种方法称为加速器质谱法。直到最近，这还依赖于粒子加速器设施中的大型机器，而且非常昂贵。现在，已经有了更小、更便宜的商业系统，但英国却没有这样的系统，尽管它是最大的民用分离钚库存的保管国。该提案建议在兰卡斯特大学安装其中一个，供整个核裂变界外部使用。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”，该协议要求企业将退役成本降低至少 20%。改进对受污染材料的钚测定将为这一目标做出重大贡献。