Hydrogen in Metals

氢在金属中普遍存在，它在生产过程中进入，在使用过程中受到腐蚀。氢会导致脆化、硬化和内部损坏。氢会降低断裂韧性，在一些金属中，氢会析出形成脆性氢化物，在载荷下会破裂。这一过程被称为延迟氢化物裂化(DHC)，对于用作化学工厂和核电站压力边界的锆合金来说，这是一个特别的问题。在压力下破裂的后果可能是高温蒸汽的猛烈释放。用于容纳核燃料的锆合金的失效可能意味着在反应堆运行期间以及之后乏燃料长期储存时放射性释放。目前，通过对操作条件进行非常保守的限制，确保了使用锆合金的安全操作。 尽管经过了几十年的研究，但关于锆中的氢仍有很多需要了解的地方。最近，申请人的研究小组报告说，锆中的氢化物冷却时会溶解，加热时会析出，这真的很奇怪。我们预计会出现相反的情况：物质加热时会溶解，冷却时会沉淀。这些观察结果是史无前例的，正在开发的解释也是前所未有的。这种奇怪的行为只发生在很小的温度范围内，但它发生在反应堆和化工厂运行的温度。随着氢的进入，锆的性质如何变化的影响开始显现：氢扩散发生变化，延迟氢化物裂解发生在你预计不会形成氢化物的温度。 DHC的型号自70年代中期以来一直在开发。在过去的10年里，这些模式受到了严厉的质疑。申请人的研究小组为DHC引入了一个新的模型，该模型已成功地用于预测广泛的实验结果；这是史无前例的和令人兴奋的，并纳入了对潜在物理的更好理解。一个可靠可靠的DHC物理模型将导致更好地预测锆组分的故障，从而提高化工厂、核反应堆和长期储存的乏核燃料的安全性。 关于氢和氢化物在金属中的行为，特别是在锆合金中的行为，正在出现一种新的理解。这项建议的目标是与一群有才华的学生一起系统地探索这一新理解的含义，并将其提升到更高的水平。

Hydrogen is ubiquitous in metals, it enters during production and from corrosion during service. Hydrogen causes embrittlement, hardening and internal damage. Hydrogen can reduce fracture toughness and, in some metals, hydrogen can precipitate forming brittle hydrides that crack under load. The process is called Delayed Hydride Cracking (DHC) and it is a particular problem for zirconium alloys that are used in chemical and nuclear plants as pressure boundaries. The consequence of cracking under pressure can be violent release of high temperature steam. Failure of zirconium alloys used to contain nuclear fuel could mean release of radioactivity during reactor operation and later when the spent fuel is in long-term storage. Currently, safe operation with zirconium alloys is ensured by placing very conservative limits on operating conditions. In spite of decades of research there is still much to learn about hydrogen in zirconium. Recently, the applicant's research group has reported hydrides in zirconium dissolving when cooled, and precipitating when heated, which is truly bizarre. We expect the opposite to happen: things dissolve when heated and precipitate when cooled. These observations are unprecedented, and so is the explanation being developed. This bizarre behavior only happens over a small temperature range, but it happens at the temperatures where reactors and chemical plants operate. The implications for how properties of zirconium change with hydrogen ingress are beginning to show: hydrogen diffusion changes, and delayed hydride cracking occurs at temperatures where you do not expect hydrides to form. Models of DHC have been developing since the mid-70s. In the last 10 years these models have been critically questioned. The applicant's research group have introduced a new model for DHC that has successfully been used to predict a broad spectrum of experimental results; this is unprecedented and exciting, and incorporates a better understanding of the underlying physics. A reliable robust physical model of DHC will lead to better predictions of failures of zirconium components and, thus, improved safety for chemical plants, nuclear reactors and spent nuclear fuel in long-term storage. A new understanding is emerging of how hydrogen and hydrides behave in metals, and in zirconium alloys in particular. The goal of this proposal is to have fun with a group of talented students systematically exploring the implications of this new understanding, and taking it to a higher level.