Capture gamma-ray Assessment in Nuclear Energy (C-GANE)

核能是通过两个原理获得的：1)裂变，通过诱导重原子分裂成更轻的元素来释放能量；2)聚变，通过将轻原子融合在一起形成更重的原子来释放能量。裂变是成熟的，在世界上大部分地区都在使用；核聚变是重要的研究和投资的主题，因为它有可能产生低碳，不间断的能源生产，而不会产生裂变产生的高活性放射性废物。当裂变反应堆中使用的燃料达到其使用寿命时，它被认为已经用完，要么被储存起来，要么被溶解和分离（后者被称为再加工）。普遍的期望是，裂变反应堆中未经过再处理的乏燃料将以完整的燃料组件的形式处置。然而，到目前为止，在英国，大部分核反应堆都被储存在水下，以确保其得到满意的冷却，并屏蔽来自核反应堆的辐射，这导致一些反应堆组件内部有水。同样，如果燃料材料以无序形式存在，例如与加工作业和事故产生的杂项废物（称为含燃料材料- FCM）有关，则通常将其储存在筒仓中，并且需要再次评估存在的水的丰度。重要的是要了解乏燃料和FCM在永久处置（例如在地下储存库中）之前的水丰度情况的程度，因为水对防止意外核反应的燃料稳定性构成重大影响，这可能影响燃料的储存方式以及与储存储存库设计有关的安全情况。最近一个相关的例子，也许是最近最引人注目的例子，涉及切尔诺贝利的FCM。这在2021年得到了媒体的广泛报道，当时观察到它发出的中子辐射水平正在增加。有问题的碎片被一层新的保护层所覆盖，以保护它不受元素的影响，这引起了人们的怀疑，即这导致了材料的裂变率上升。在含有燃料的材料中，中子主要是由铀-235的裂变产生的，令人担心的是，碎片中含水量的下降会导致这种情况增加，最终可能导致无法控制的能量释放。然而，由于水的减少减少了对中子的屏蔽和吸收，使更多的中子得以释放，或者由于α粒子的中子发射反应的增加，或者由于使用的中子探测器在更高的能量下反应更有效，这些都可能导致铀-235诱导裂变升级的严重影响。而不是测量中子通量，这是切尔诺贝利FCM关注的来源，通过检测中子被周围材料中的同位素捕获时发出的伽马射线，可能会对这个复杂问题有更深入的了解。这样做的好处是，伽马射线具有产生它们的同位素特有的能量，而且相对容易测量：这是本提案的重点。例如，氢发射的伽马射线具有容易识别的2.223兆电子伏能量，这可能是水含量变化的特征，并且可能与中子环境的变化分开。有趣的是，除了中子发射之外，测量核聚变功率的少数几种方法之一也是研究这些发射，例如考虑氘-氚反应的16.7兆电子伏特发射。在这个项目中，我们打算把这些机会结合起来，以确定裂变和聚变能是否可能受益于高能捕获伽马能谱。

Nuclear energy is made available via two principles: 1) fission, in which energy is released by inducing heavy atoms to split into lighter elements, and 2) fusion, where energy is released by fusing light atoms together forming heavier ones. Fission is mature and is used throughout much of the world; fusion is the subject of significant research and investment, due to its potential to yield low-carbon, uninterrupted energy production without the yield of high-active radioactive waste produced in fission.When the fuel used in fission reactors reaches the end of its useful life it is deemed spent, and is either stored or dissolved and separated (the latter known as being reprocessed). The widespread expectation is that spent fuel from fission reactors that is not reprocessed will be disposed of in the form of intact fuel assemblies. However, thus far in the UK much of it has been stored under water to ensure that it is cooled satisfactorily and that the radiation from it is shielded, and this has resulted in some of the assemblies having water inside them. Similarly, where fuel material exists in disordered form associated with, for example, miscellaneous wastes from processing operations and accidents (known as fuel containing materials - FCM), often it has been stored in silos and again the abundance of water present needs to be assessed. It is important to understand the extent of the situation concerning water abundance in spent fuel and FCM prior to it being disposed of permanently (for example in an underground repository) because the water constitutes a significant influence on the stability of the fuel against an inadvertent nuclear reaction, and this could influence how it is stored and the safety case concerning the design of the repository it is stored in.A relevant recent example, and perhaps the highest-profile illustration of late, concerns the FCM at Chernobyl. This received widespread media coverage in 2021 when it was observed that the level of neutron radiation emitted by it was increasing. The debris in question had been shrouded by a new cover erected over the site to protect it from the elements and the suspicion arose that this was causing the fission rate in the material to escalate. Neutrons arise in materials containing fuel predominantly from fission in uranium-235, with the concern being that a fall in the water content in the debris was causing this to increase with the ultimate potential for uncontrolled energy release. However, the emission might also increase due to reduced shielding and absorption of neutrons by a reducing quantity of water, enabling more neutrons to get out, or by an increase in neutron-emitting reactions by alpha particles or due to the neutron detectors being used responding more efficiently at higher energies, none of which have implications as serious as an escalation in induced fission on uranium-235.Rather than measuring the neutron flux, as was the source of concern for the FCM at Chernobyl, greater insight might be gained concerning this complex problem by detecting the gamma rays that are emitted when neutrons are captured by isotopes in the surrounding materials. This has the advantage that the gamma rays have energies that are characteristic of the isotope producing them and that they are measured relatively easily: this is the focus of this proposal. For example, hydrogen emits gamma rays with an easily-identifiable energy of 2.223 MeV which could be characteristic of changes in water content and which might be separable from changes in the neutron environment. Interestingly, one of the few ways to measure fusion power aside from the neutron emission is also to study these emissions, by for example considering the 16.7 MeV emission from the deuterium-tritium reaction. In this project, we intend to bring together these opportunities to determine whether fission and fusion energy might benefit from high-energy capture gamma spectroscopy.