Simultaneous Corrosion/Irradiation Testing in Lead and Lead-Bismuth Eutectic: The Radiation Decelerated Corrosion Hypothesis (RC-3)

核裂变发电在为英国提供低碳足迹电力方面发挥着至关重要的作用。目前英国的核反应堆正在迅速老化，所有这些反应堆都计划在未来12年内退役。如果没有替代，它们产生的电力，约占英国总电力的20%，将需要其他来源提供，例如化石燃料发电站。这将对英国温室气体排放和气候变化造成不利影响。为了在2050年之前成功实现脱碳，英国迫切需要新建未来的裂变反应堆。液态铅（Pb）和铅铋共晶（LBE）冷却快堆在裂变反应堆中具有最佳的功率密度和经济性。然而，几十年来，由于担心Pb/LBE腐蚀和辐射对结构材料的综合影响，这些反应堆的发展一直停滞不前。此外，问题是，要真正测试腐蚀有多严重，人们要么必须在现有的研究反应堆中进行实验，要么确实建造一个全新的铅或lbe冷却的研究反应堆。在没有对材料性能的初步了解和预测的情况下，建造和许可一个测试反应堆将是一项挑战。需要一种更快的方法来研究Pb/LBE冷却快堆材料的辐照和腐蚀组合！在这里，我们解决了这个问题：我们在美国麻省理工学院的项目合作伙伴开发了一种新的，独一无二的设备，可以同时将材料暴露于Pb/LBE腐蚀和质子原位照射下。质子被用来模拟裂变反应堆中中子的作用。虽然质子不能完全模拟中子造成的破坏，但它们很好地捕捉到了关键机制。最重要的是，这些实验比反应堆内材料测试更快、更便宜。利用这个新工具，我们将探索目前领先的五种用于Pb/LBE快堆包层和结构部件的合金的性能。我们还将把结果与更传统的Pb/LBE腐蚀测试进行比较，以确保新的组合式辐照和腐蚀设备的性能符合预期。暴露后，项目团队的牛津合作伙伴将对样品进行分析，以确定Pb/LBE在辐照下的腐蚀过程，以及与没有辐照的Pb/LBE腐蚀有何不同。奇怪的是，我们的初步结果表明，辐照减缓了腐蚀的速度！为了探索和理解这种行为，我们将对暴露后样品的结构和化学成分进行表征，从宏观到原子尺度。这种微观结构特征将与美国项目合作伙伴在北卡罗莱纳州立大学进行的暴露材料的机械测试相结合。总的来说，这个项目的结果将最终解决同步辐照如何改变铅/LBE冷却快堆合金的腐蚀行为。这将使我们能够确定哪一种被测试的候选合金性能最好，以及在腐蚀和辐照联合过程中控制其降解的关键机制是什么。这些信息对于克服目前Pb/LBE冷却快堆发展的停滞不前，以及对结构和包层材料进行定向优化至关重要。

Nuclear fission power plays a vital role in supplying the UK with low carbon footprint electricity. The current UK fleet of nuclear reactors is rapidly ageing, and all of these reactors are scheduled to be removed from service within the next 12 years. Without replacement, the electricity they generate, ~20% of total UK electricity, will need to be provided by other sources, e.g. fossil fuel power stations. This would be detrimental to UK greenhouse gas emissions and contribution to climate change. For successful decarbonisation by the 2050s, UK new build of future fission reactors is urgently needed. Liquid lead (Pb) and lead-bismuth eutectic (LBE) cooled fast reactors promise the best power density and economics among fission reactors. However, for decades now the development of these reactors has been stuck because of concerns about the combined effect of Pb/LBE corrosion and irradiation on the structural materials they would use. Moreover, the problem is that to actually test how bad the corrosion is, one would either have to setup an experiment in an existing research reactor or indeed build a whole new Pb or LBE-cooled research reactor. This would be prohibitively costly, slow and it would be challenging to build and license a test reactor without initial understanding and prediction of material performance. A much faster way of studying combined irradiation and corrosion of materials for Pb/LBE cooled fast reactors is needed!Here we address this problem: Our project partners at MIT, USA, have developed a new, one-of-a-kind facility that allows the simultaneous exposure of materials to Pb/LBE corrosion and insitu irradiation with protons. The protons are used to mimic the effect of neutrons in a fission reactor. Whilst protons don't perfectly mimic the damage caused by neutrons, they capture the key mechanisms well. Most importantly these experiments are much quicker and cheaper than e.g. in-reactor material testing. Using this new tool, we will explore the performance of five of the current front-runner alloys for cladding and structural components in Pb/LBE fast reactors. We will also compare the results against more traditional Pb/LBE corrosion tests to make sure the new combined irradiation and corrosion facility performs as anticipated. After exposure, the Oxford partners of the project team will then analyse the samples to determine how Pb/LBE corrosion proceeds in the presence of irradiation, and how this differs from Pb/LBE corrosion without irradiation. Curiously our initial results show that irradiation slows down the rate of corrosion! To explore and understand this behaviour, we will perform characterisation of the structure and chemical composition of samples after exposure, from the macroscopic down to the atomic scale. This microstructural characterisation will be combined with mechanical testing of the exposed materials carried out by US project partners at the North Carolina State University. Overall the results from this project will finally address how simultaneous irradiation modifies the corrosion behaviour of alloys for Pb/LBE cooled fast reactors. It will allow us to identify which of the tested candidate alloys performs best and what the key mechanisms are that control its degradation during combined corrosion and irradiation. This information is vital for overcoming the current stagnation of progress in the development of Pb/LBE cooled fast reactors, and to allow directed optimisation of the structural and cladding materials they require.