Laser-driven multi-modal probe beams for nuclear waste inspection

这项提议旨在开发一种革命性的新工具，用于使用激光驱动的X射线和中子束脉冲对核废料包装进行远距离检查。这将是布里斯托尔大学界面分析中心(IAC)、Sellafield Limited、贝尔法斯特女王大学(QUB)和STFC中央激光设备(CLF)之间的一个合作项目。通过在很短的时间内发射极高能量的激光，产生强烈的X射线辐射斑点并投射到探测器板上。以类似于医用x射线的方式，放置在明亮的x射线源和照相胶片或数字图像板之间的任何物体都被详细捕捉。然而，因为使用了非常高的能量，所以对含有铀废料的包裹进行成像是可能的。铀废料是地球上密度最大的材料之一。自1952年以来，塞拉菲尔德一直负责安全存储和再处理英国所有的核废料。经过几十年的研究和开发，产生了更易管理的核废料形式。然而，仍然存在一些问题，特别是自20世纪60年代以来一直储存的老化的“遗留”核废料。在考虑在地质处置设施中长期储存之前，需要确定废物和安全壳容器的成分和降解状态。由于储存过程中形成的放射性和危险的腐蚀产物，对废旧集装箱进行破坏性调查被认为太危险了。因此，建议对容器进行非破坏性、非破坏性的评估。为了目视检查核废料包装的内部部件，使用高能X射线来创建样品的图像。产生X射线的典型方法既达不到所需的分辨率，也达不到穿透大型密集废物容器的能量。因此，有人建议利用CLF的千瓦级火神激光器来产生这项分析所需的高能X射线。此外，火神激光设施能够产生与高能X射线平行的中子束。通过用中子束探测废物容器，里面包含的任何裂变材料都会经历少量的裂变，并释放出二次中子。根据反应的裂变材料的不同，发射出的中子将产生一个独特的信号，可以用来识别样品中存在的特定同位素。对这些数据的分析具有同位素量化的潜力，从而与同位素不同、放射性低得多的铀-238相比，确定高放射性铀-235的确切数量。虽然这项提议的最初目标是通过单次激发方法确定样品的特征，但最终目标是开发一种能够每秒发射多达10次的系统，方法是建造一种占地面积小的高能偶极激光器，以及能够快速获取数据的相应传感器。由于预计会有这样一个系统，该项目的一个组成部分旨在改进现有的探测器技术，重点是快速图像捕获和中子探测。该项目的最后部分是产生一个商业案例，以寻求最终开发一个快速发射分析系统，以形成核废料包裹扫描设施的基础。与CT扫描非常类似，通过在多次图像采集过程中旋转废旧容器，可以构建内容物的3D轮廓。这项技术将使我们能够深入到废物容器内，并详细评估其内容物，而不会对潜在的有毒、自燃和放射性内容物进行任何破坏性调查或干扰。我们认为，这项技术将具有极好的全球出口潜力，可以向其他产生核废料的国家出口。

This proposal aims to develop a revolutionary new tool for the stand-off inspection of nuclear waste packages using laser-driven x-rays and neutron beam pulses. This will be a collaborative project between the University of Bristol's Interface Analysis Centre (IAC), Sellafield Limited, Queen's University Belfast (QUB) and the STFC Central Laser Facility (CLF). By firing an extremely high-energy laser for a very short duration, an intense spot of x-ray radiation is generated and projected towards detector plates. In a similar manner to medical x-rays, any object placed between the bright source of x-rays and either photographic film or digital image plates, is captured in detail. However, because a very high energy is used, imaging of packages containing uranium waste, one of the densest materials on Earth, is possible.Since 1952, Sellafield has been responsible for safe storage and reprocessing of all the UK's nuclear waste. Decades of research and development have resulted in more manageable forms of nuclear waste. However, a number of problems remain, particularly with the ageing 'legacy' nuclear waste that has been stockpiled since the 1960s. Before long term storage in a geological disposal facility is considered, the composition and degradation state of the waste material and containment vessels needs to be established. Due to the radioactivity and dangerous corrosion products formed during storage, a destructive investigation of the waste containers is considered far too hazardous to be performed. Therefore, a non-destructive, stand-off evaluation of the containers is proposed.For a visual inspection of the internals of a nuclear waste package, high-energy x-rays are used to create an image of the sample. Typical means of producing x-rays do not achieve either the resolution required or the energy to penetrate through the large, dense waste containers. Therefore, it has been proposed that the petawatt Vulcan laser at the CLF is utilised to generate the necessary high-energy x-rays required for this analysis.In addition, the Vulcan laser facility is capable of producing a beam of neutrons in parallel with the high-energy x-rays. By probing the waste containers with a neutron beam any fissile material contained inside will undergo a small amount of fission and emit secondary neutrons. Depending on the fissile material that reacts, the emitted neutrons will generate a unique signature which can be used to identify the particular isotope present in the sample. Analysis of this data holds the potential for isotopic quantification, thus identifying the exact quantity of highly radioactive uranium-235 compared to the isotopically different, and far less radioactive, uranium-238.Whilst the initial aims of this proposal are for characterisation of samples via a single-shot approach, the end goal is the development of a system capable of firing up to ten times a second by construction of a small footprint, high-energy DiPOLE laser with the corresponding sensors capable of rapid data acquisition. In anticipation of such a system, one component of this project aims at improving existing detector technology with a focus on rapid image capture and neutron detection.The final section of the project is the production of a business case to pursue the eventual development of a fast firing analysis system to form the basis of a nuclear waste package scanning facility. Much like CT scanning, by rotating the waste container during multiple image acquisition a 3D profile of the contents can be constructed. This technique would allow us to probe deep inside the waste containers and assess their contents in detail without any destructive investigation or disturbance to the potentially toxic, pyrophoric, and radioactive contents. We consider that this technology would have excellent global export potential to other nations producing nuclear waste.