Zirconium alloys for high burn-up fuel in current and advanced light water-cooled reactors

为了提高现代核反应堆的效率，降低运行成本并最大限度地减少核废料，燃料制造商与工厂运营商和核废料机构正在努力开发燃料组件，这种燃料组件可以比目前实现的运行时间长得多。由于铀浓缩技术在过去二十年中取得了重大进展，现在是燃料包层材料限制了燃料组件产生的能量水平（核工业称之为燃烧）。增加所谓的燃料组件燃耗将改善民用核反应堆的燃料经济性/燃料使用量，延长换料周期（即减少反应堆换料的停机次数），从而降低运营成本和核废料。由于锆合金在水冷堆环境中的良好性能和对中子的透明性，现代核反应堆采用锆合金作为燃料包壳材料。包层材料在这种环境下工作的时间（因此可以从燃料组件产生的能量水平）与腐蚀特性成正比。更持久的包层材料需要具有更强保护氧化层的锆合金，这将避免任何加速腐蚀，氧化层的分离，并防止氢的吸收。到目前为止，在这一领域的任何发展都是纯粹的经验，并没有导致所需的步骤变化，这将允许操作燃料组件到所需的燃耗。该应用程序的科学基础是通过研究在高压灭菌器环境中进行腐蚀测试时，商用和模型合金中所有相关微观结构特征、局部应力、氧化物中的电子缺陷的影响和相互关系来解决这些问题。这就要求项目团队在一个连贯的、跨学科的项目中使用最新一代的分析技术。此外，我们的工业合作伙伴提供额外的专业设施，如高压灭菌器或熔化设施，以生产模型合金。关键主题是发展对腐蚀过程的机械理解，以实现基于物理模型的开发，这将使设计和充分利用优化的合金，以延迟分离氧化和氧化生长。这项研究将由多所大学组成的团队进行，鼓励博士生和博士后研究助理组成一个核心研究小组，共同利用来自不同机构的世界级设施。

In order to improve the efficiency of modern nuclear reactors, reduce operating costs and minimise nuclear waste the fuel manufacturers together with plant operators and nuclear waste agencies are trying to develop fuel assemblies, which can operate for substantially longer times than what is currently achieved. Since Uranium-enrichment technology has progressed significantly in the last two decades it is now the fuel cladding material that limits the level of energy produced from a fuel assembly (termed burn-up by the nuclear industry). Increasing the so-called burn-up of fuel assemblies will improve the fuel economy/fuel usage of civil nuclear reactors, extend refuelling cycles (i.e. reduce the number of shutdowns for refuelling the reactor), and hence reduce the operating costs and nuclear waste. In modern nuclear reactors fuel cladding is based on zirconium alloys due to their good performance in the environment of water-cooled reactors and their transparency to neutrons. The time the cladding material can operate in such an environment (and therefore the level of energy that can be produced from a fuel assembly) is proportional to the corrosion properties. Longer lasting cladding material would require zirconium alloys with a more protective oxide layer, which would avoid any accelerated corrosion, breakaway of the oxide layer and protect against hydrogen pick-up. To date, any development in this area has been purely empirical and has not resulted in the required step change, which would allow operating the fuel assemblies to the desired burn-up. The scientific basis of this application is to address these issues by studying the influence and inter-relationships of all relevant microstructural features, local stresses, electronic defects in the oxide, in both commercial and model alloys when corrosion tested in an autoclave environment. This requires the project team to use the latest generation of analytical techniques in a coherent, interdisciplinary program. In addition our industrial partners provide access to additional specialist facilities such as autoclaves or melting facilities to produce model alloys. The key theme is to develop a mechanistic understanding of the corrosion process to enable the development of physically-based models, which will enable the design and full exploitation of alloys optimized to delay breakaway oxidation and oxidation growth. The research will be undertaken by a multi-university team, encouraging PhD students and post-doctoral research associates to form a core group of researchers who work together to exploit world-class facilities from different institutions.