'OptiClean' - Optimised laser cleaning for safe nuclear decontamination and decommissioning

2011年3月11日午餐后不久，东北9.0级大地震引发的15米高的海啸吞没了福岛第一核电站(FDNPP)--摧毁了核电站、其重要的周边基础设施以及提供紧急反应堆堆芯冷却的多层安全层。由于缺乏持续的堆芯冷却供应，在接下来的几天里，为了应对反应堆内的临界温度和压力，注入了海水，作为提供紧急堆芯冷却的最后手段。然而，这种孤注一掷的努力是不够的，每个反应堆压力容器(RPV)的温度都上升到超过2,000摄氏度；导致核燃料组件中包含的铀熔化(部分或全部)并垂直向下通过RPV腐蚀到主安全壳(PCV)的底部--并覆盖了广泛的PCV的内部体积。在英国，塞拉菲尔德的厂址包括第一座商业发电站(Calder Hall，有四个Magnox反应堆)和生产钚的WindScale堆1和2，这些堆为英国最初的核武器计划提供了燃料。匆忙组装导致对报废退役、废物管理和运营后退役几乎没有规划，这意味着这些设施仍然存在很高的危险。然而，塞拉菲尔德的危险消除挑战并不是英国独有的，大量的Magnox加油站也在长期的“维护和维护”之前开始“加速退役”。在整个NDA产业中，许多最紧迫和最复杂的退役挑战涉及到受辐射污染的表面的净化，人们已经考虑了许多方法来解决这个问题，激光清洗成为最有希望的候选方案。激光消融(或“激光清洗”)是一种新兴的退役工具，用于国际核工业快速净化表面固定的放射性材料，最近被确定为一种在整个英国NDA庄园使用的“有前途的技术”。它对核退役特别有吸引力，因为它不仅是非接触的，而且比其他物理和化学方法产生的次生固体和水废物的量要少得多。然而，仍然存在一些基本的挑战，阻碍了该技术的广泛实施：-该技术的烧蚀性质可能会产生局部的大气污染。-由于烧蚀的放射性物质具有空气中的颗粒物性质，废物收集和处理变得复杂。-必须进行额外的之前和之后的表征调查，以计划净化活动和评估激光清洗的质量。这项及时、跨学科和有影响的建议通过开发新的微粒遏制和收集战略，与创新的光学表征相结合，用于规划和评估清洁活动，从而解决这些和其他挑战。通过这种方式，它将减少激光清洗的负担、风险和管理费用，使其在国际上得到更广泛的使用。这将特别适用于FDNPP，但也适用于塞拉菲尔德和英国其他遗留的核设施。我们将利用实验室评估的知识，制作一个光纤耦合的‘OptiClean’原型系统，用于集成到我们的LBR-SuperDroid上，这是为NNUF计划开发的。该平台由一个SuperDroid HD2组成，这是一个大型履带式机器人平台，顶部安装了一个KUKA LBR IIWA 14机器人操作手。其可跟踪性允许远程门口规模的访问，具有额外的爬楼梯能力，而LBR是一种七自由度机器人机械手，具有力反馈传感功能，实现人类安全的交互。

Shortly after lunch on the 11th March 2011, a 15 m high tsunami triggered by the magnitude 9.0 Great Tohoku earthquake engulfed the Fukushima Daiichi Nuclear Power Plant (FDNPP) - crippling the site, its essential surrounding infrastructure and the multiple safety layers the provided emergency reactor core cooling. Resulting from this absence of sustained core cooling provision, over the following days and in response to critical temperatures and pressures within the reactors, seawater was injected as a final resort to provide emergency core cooling. However, this desperate effort was insufficient, and temperatures rose in each of the reactor pressure vessels (RPVs) to in-excess of 2,000C; causing the uranium contained within the nuclear fuel assemblies to melt (partially or fully) and corrode vertically downwards through the RPV, into base of the primary containment vessel (PCV) - as well as coating the internal volume of the extensive PCV. In the UK, the Sellafield site includes the first commercial power-generating station (Calder Hall, with four Magnox reactors) and the plutonium-producing Windscale Piles 1 and 2, that fuelled the UK's original nuclear weapons programme. The haste to assemble led to little planning for end-of-life retirement, waste management and post-operational decommissioning, meaning that such facilities still present high hazards. The hazard removal challenges at Sellafield are, however, not unique in the UK, with the large number of Magnox stations also embarking on "accelerated decommissioning" ahead of long-term "care and maintenance". Many of the most pressing and complex decommissioning challenges across the NDA estate concern the decontamination of radiologically contaminated surfaces, with numerous methods having been considered to address this, and laser cleaning emerging as the promising candidate. Laser ablation (or "laser cleaning") is an emerging decommissioning tool for the international nuclear industry to rapidly decontaminate surface-fixed radioactive materials, having recently been identified as a "promising technique" for use across the UK NDA Estate. It is particularly attractive for nuclear decommissioning as it is not only non-contact, but also produces much smaller volumes of secondary solid and aqueous wastes than alternative physical and chemical methods. However, some fundamental challenges remain which prevent widespread implementation of the technique:- The ablative nature of the technique can generate localised atmospheric contamination.- Waste collection and disposal are complicated due to the airborne particulate nature of the ablated, radioactive material.- Additional 'before' and 'after' characterisation surveys are necessary to plan the decontamination activities and assess the quality of laser cleaning.This timely, cross-disciplinary, and impactful proposal addresses these and other challenges by developing novel particulate containment and collection strategies, integrated with innovative optical characterisation, for planning and assessing cleaning activities. In this way, it will reduce the burden, risks and overheads of laser cleaning, leading to its broader international utilisation. This would be particularly applicable at FDNPP, but also at Sellafield and other legacy nuclear sites in the UK. We will use knowledge from the laboratory assessments to make a prototype fibre coupled, 'OptiClean' system for integration onto our LBR-SuperDroid, as developed for the NNUF programme. The platform consists of a SuperDroid HD2, a large tracked robotic platform, with a KUKA LBR IIWA 14 robotic manipulator mounted on the top. Its tracked nature allows for remote doorway-scale accesses with additional stair-climbing capabilities whilst the LBR is a seven degrees of-freedom robotic manipulator with force feedback sensing for human-safe interaction.