US DOE IRP on Simulation of Neutron Irradiation

在高剂量裂变反应堆概念(Gen-4)中，结构材料必须在超过400摄氏度的温度下经受住高达200dpa的破坏。在如此高的损伤水平下，主要的退化模式可能是由孔洞膨胀和相稳定性驱动的。传统上，了解辐射引起的材料变化的研究是通过在测试反应堆中进行辐射效应实验，然后进行全面的辐射后表征计划来进行的。通过提供预测能力，辐射损伤过程的建模有助于减少对覆盖整个参数空间的实验的需要。然而，测试反应堆造成辐射损害的速度不会比商业反应堆快得多，这意味着辐射损害研究往往无法在运行过程中发现的问题之前取得进展。此外，进行试验堆实验的成本非常高，极大地限制了可以支持的实验数量。解决这一问题的一个有希望的解决方案是使用离子辐射，这种辐射可以产生很高的损伤率，而残余放射性很少或根本没有。离子辐照有很多优点。剂量率远高于中子照射，这意味着200 dpa可以在几天或几周内达到，而不是几十年。样本没有放射性。在反应堆中，温度、损伤率和损伤程度的测量是困难的，导致依赖于计算来确定总剂量和估计辐照温度。相比之下，离子辐照已经发展到可以非常好地控制和监测温度，并在整个辐照过程中以极高的精度连续测量损伤率和总损伤的程度。然而，离子辐照有几个潜在的缺点：辐照材料的体积小，高损伤率对所产生的微观结构的影响，以及需要考虑在反应堆中发生的重要的转化反应，如产生He和H。理解和建模微观结构与性能的关系，结合微样品制备和测试的发展，有望将有限的辐照体积的缺点降至最低。解释蜕变反应的策略是同时用重离子照射目标，同时用He和/或H轰击它。这样的过程需要在双束或三束设备中耦合多个加速器。为了将离子辐照用于研究中子辐照，必须尽可能地再现中子辐照后的微观结构和中子引起的宏观性质的变化。由于这些微结构非常复杂，因此验证离子辐照微结构是否类似于反应堆辐射的任务也相应地复杂。这项任务最好使用与建模紧密结合的最先进的实验技术的组合来解决，这可以产生对缺陷发展过程的机械理解，同时在实验设计和理论建模中考虑到尽可能多的上述因素。

In high dose fission reactor concepts (GEN-4) structural materials must survive up to 200dpa of damage at temperatures in excess of 400C. At such high damage levels, the major degradation modes are likely to be driven by void swelling and phase stability. Traditionally, research to understand radiation-induced changes in materials is conducted via radiation effects experiments in test reactors, followed by a comprehensive post-irradiation characterization plan. Modelling of the radiation damage process helps to reduce the need for experiments covering the entire parameter space by providing predictive capabilities. However, test reactors cannot create radiation damage significantly faster than that in commercial reactors, meaning that radiation damage research often cannot "get ahead" of problems discovered during operation. In addition, the cost of conducting test reactor experiments is very high limiting dramatically the number of experiments that can be supported. A promising solution to the problem is to use ion irradiation that can produce high damage rates with little or no residual radioactivity. The advantages of ion irradiation are many. Dose rates are much higher than under neutron irradiation which means that 200 dpa can be reached in days or weeks instead of decades. Samples are not radioactive. Measurement of temperature, damage rate and damage level is difficult in reactor, resulting in reliance on calculations to determine the total dose, and estimate irradiation temperature. By contrast, ion irradiations have been developed to the point where temperature is extremely well controlled and monitored, and damage rate and total damage are also measured continuously throughout the irradiation and with great accuracy. However, ion irradiation has several potential drawbacks; the small volume of irradiated material, the effect of high damage rate on the resulting microstructure, and the need to account for important transmutation reactions that occur in reactor, such as the production of He and H. Understanding and modelling the microstructure-property relationship allied with the development of micro-sample fabrication and testing, hold the promise for minimizing the drawback of limited irradiated volume. The strategy to account for transmutation reactions is to simultaneously irradiate a target with heavy ions while also bombarding it with He and/or H. Such a process requires multiple accelerators coupled in a double or triple beam facility. To qualify ion irradiation to study neutron irradiation it is necessary to reproduce as best as possible both the neutron irradiated microstructure and the neutron-induced macroscopic property changes using ion irradiation. Because these microstructures are very complex, the task of verifying that the ion irradiation microstructures are similar to that of a reactor irradiation is correspondingly complex. This task is best addressed using a combination of state of the art experimental techniques closely coupled to modelling, which can yield mechanistic understanding of the defect development process, while taking into account in the experimental design and theoretical modelling as many as possible of the factors outlined above.