Enabling 3D atomic-scale imaging of hydrogen to investigate hydrogen embrittlement of zirconium alloy fuel cladding in fission reactors

锆合金在核反应堆中起着至关重要的作用，在燃料棒组件中提供密封屏障，在燃料棒的整个使用寿命内，燃料棒组件可以承受核反应堆环境中的高中子通量和高温。这确保了棒内的核燃料与反应堆的其余部分安全隔离。然而，尽管它有许多优点，燃料棒组件的寿命往往受到锆棒腐蚀行为的限制。氢化物可以在杆内形成，改变杆的尺寸和应力状态，使其易于开裂。因此，为了防止棒的失效，这些棒在其使用寿命之前就被从反应堆中移除。在燃料必须被移除和处理之前，核反应中仅有6%的能量可以在反应堆中被提取。这将导致更高的能源成本，更关键的是，反应堆输出的废物量也会增加。这种废物是除了储存的废物在英国，很难储存和处置-再次复合损失。因此，我们寻求更好地了解这些材料的相互作用，以尽量减少浪费，并满足英国法律规定的二氧化碳目标。因此，了解这些材料的化学性质及其与氢的相互作用至关重要——该项目旨在确定氢是如何与这些锆合金相互作用的，并研究氢分布下材料的机械变形和不同化学性质的行为。该项目将开发高度新颖的方法，以适应原子探针断层扫描（APT），结合同位素分析，以确定氢在锆样品中的原子尺度分布，并将其与限制包层材料安全使用寿命的材料行为联系起来。所提供的新见解将有助于为开发新的合金方法提供更长的燃料棒提供信息，并告知如何设计锆合金以优化其在反应堆环境中的使用寿命。这种能力代表了一种研究锆合金中氢的全新方法。此前，许多研究人员已经使用APT来研究锆合金的氧化区和亚氧化区，以更好地了解合金元素在锆中的腐蚀作用。然而，该项目将进行新的研究，以提供原子尺度上的直接实验证据，以了解氢如何与锆相互作用，以及如何将氢裂解效应最小化。该项目将提供暴露于氢大气中的Zr材料（如Zr-4）的直接实验数据，并提供氢如何与主体材料的化学和微观结构相互作用的定量数据。它将确定这些材料中氢的位置和浓度，以了解氢是如何在反应堆的水区中产生的，如何运输到材料中并降解它们。该项目属于EPSRC能源研究领域。它将与国家核实验室和劳斯莱斯的工业伙伴合作进行。

Zirconium alloys have a critical role in nuclear reactors, providing a hermetic barrier in the fuel rod assembly, which is designed to withstand the high neutron flux and high temperatures of a nuclear reactor environment, for the full operational life of the fuel rod. This ensures that the nuclear fuel contained in the rod is safely isolated from the remaining parts of the reactor. However, despite its many advantages, the life of the fuel rod assembly is often limited by the corrosion behaviour of the zirconium rod. Hydrides can form within the rod, altering the dimensions and stress states of the rod, making it prone to crack. Thus to prevent failure of the rods, these are removed from the reactor well in advance of their useful life. As little as 6% of the energy available in the nuclear reaction can be extracted in the reactor, before the fuel must be removed and disposed of. This leads to higher costs for energy, and critically, higher waste volumes in the reactor output. This waste is in addition to the stockpiled waste within the UK, and is difficult to store and dispose of - again compounding loss. As such, we seek to better understand the interaction of these materials, to minimise waste and to meet the legally mandated carbon dioxide goals for the UK. Understanding the chemistry of these materials, and their interaction with hydrogen is therefore critical - this project seeks to identify how hydrogen interacts with these Zirconium alloys, and to examine the behaviour of mechanical deformation and different chemistries of the material on the hydrogen distribution. This project will develop highly novel methodologies to adapt Atom Probe Tomography (APT), in conjunction with isotopic analysis, to identify how hydrogen is distributed at the atomic-scale within a zirconium sample, and correlate this to the material behaviours that limit the safe operating lifetime of cladding material. The new insights provided will help inform the development of new alloying methods to provide longer-life fuel rods, and inform how zirconium alloys can be designed to optimise their operational lifetimes within a reactor environment. This capability represents an entirely new approach to the study of hydrogen within zirconium alloys. Previously, APT has been used by many researchers to investigate the oxide and suboxide regions of zirconium alloys, to better understand the corrosion effects of alloying elements within Zirconium. However, this project will undertake new research to provide direct experimental evidence at the atomic scale, to understand how hydrogen interacts with zirconium, and how hydrogen cracking effects can be minimised. The project will provide direct experimental data on Zr materials (such as Zr-4) that have been exposed to hydrogen atmospheres, and provide quantitative data on how hydrogen is interacting with the chemistry and microstructure of the host material. It will identify the location and concentrations of hydrogen within these materials to understand how hydrogen, which originates within the water region of the reactor, transports into the material and degrades them. The project falls within the EPSRC Energy research area. It will be undertaken in collaboration with industrial partners at National Nuclear Laboratory and Rolls Royce.