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%）将需要由其他来源提供，例如化石燃料发电站。这将不利于英国的温室气体排放和对气候变化的贡献。为了在21世纪50年代成功脱碳，英国迫切需要建造新的未来裂变反应堆。液态铅（Pb）和铅铋共晶（LBE）冷却快堆有望在裂变反应堆中获得最佳的功率密度和经济性。然而，几十年来，这些反应堆的发展一直停滞不前，因为人们担心铅/LBE腐蚀和辐照对它们将使用的结构材料的综合影响。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，要么建造一个全新的铅或LBE冷却的研究反应堆。这将是非常昂贵的，缓慢的，并且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试验反应堆将是具有挑战性的。需要一种更快的方法来研究Pb/LBE冷却快堆材料的组合辐照和腐蚀。在这里，我们解决这个问题：我们在美国麻省理工学院的项目合作伙伴开发了一种新型的独一无二的设备，可以同时将材料暴露于Pb/LBE腐蚀和质子原位辐照。质子被用来模拟裂变反应堆中中子的效应。虽然质子不能完美地模拟中子造成的破坏，但它们很好地捕捉了关键机制。最重要的是，这些实验比反应堆内材料测试更快，更便宜。使用这种新的工具，我们将探讨目前的五个前浇道合金的性能，包壳和结构部件的铅/LBE快堆。我们还将比较结果与更传统的铅/LBE腐蚀测试，以确保新的组合辐照和腐蚀设施的预期表现。暴露后，项目团队的牛津合作伙伴将分析样品，以确定在存在辐照的情况下Pb/LBE腐蚀如何进行，以及这与没有辐照的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。这种微观结构表征将与美国项目合作伙伴在北卡罗来纳州州立大学进行的暴露材料的机械测试相结合。总的来说，该项目的结果将最终解决如何同时辐照修改铅/LBE冷却快堆合金的腐蚀行为。它将使我们能够确定哪种测试的候选合金表现最好，以及在腐蚀和辐照联合作用期间控制其降解的关键机制是什么。这些信息对于克服Pb/LBE冷却快堆发展目前的停滞至关重要，并允许直接优化它们所需的结构和包壳材料。

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.