Radiation tolerant rapid criticality monitoring (REACTION)

2011年3月，日本本州岛东北海岸附近的太平洋发生了里氏9.0级地震。这场被日本政府命名为东日本大地震的地震引发了一场巨大的海啸，淹没了超过200平方英里的沿海土地。这场毁灭性的灾难导致了一系列灾难性的故障，导致福岛第一核电站(NPP)熔毁，并引发了核紧急状态。当用于维持和控制核燃料温度的冷却系统失效时，反应堆就会熔毁。然后燃料无法控制地加热，突破安全壳，或者产生足够的压力导致爆炸。福岛的三个反应堆都发生了反应堆熔毁，导致燃料碎片聚集在反应堆底部。临界是指核裂变反应堆变得自给自足的条件。受损反应堆的无意临界性，即燃料碎片的重复性，是福岛第一核电站退役成员的主要关切。尽管不太可能出现反复无常的情况，但如果一系列情况同时发生，则不能完全排除这种情况发生的可能性。重复性产生的辐射不能穿过反应堆周围的混凝土墙，这有利于遏制眼前的风险，但对于通过对峙监测确定是否发生重复性是有问题的，直到采取补救行动为时已晚。相反，反应堆内部的辐射如此强烈，以至于它构成了另一个挑战，因为它很容易损坏电子设备并饱和辐射探测器。该项目旨在开发和部署一种坚固耐用、耐辐射的传感器系统，能够实时检测受损反应堆内部高放射性环境的细微变化，以便在发生重复性时快速检测到它。这种技术也适用于英国的核退役挑战和世界领先的聚变能源研究。

In March 2011 a magnitude-9.0 earthquake struck in the Pacific Ocean off the northeast coast of Japan's Honshu island. Named the Great East Japan Earthquake by the Japanese government, it triggered a massive tsunami that flooded more than 200 square miles of coastal land. This devastating disaster caused a series of catastrophic failures resulting in the meltdown of the Fukushima Daiichi Nuclear Power Plant (NPP) and initiated a nuclear emergency. Reactor meltdown occurs when the cooling systems used to maintain and control the temperature of the nuclear fuel fails. The fuel then heats up uncontrollably and breaches the containment vessel or creates enough pressure to cause an explosion. Reactor meltdown occurred at all three reactors at Fukushima, resulting in fuel debris collecting at the base of the reactors.Criticality is the condition where a nuclear fission reactor becomes self-sustaining. Unintentional criticality of a stricken reactor, i.e. recriticality, of the fuel debris is a major concern for the decommissioning members of the Fukushima Daiichi NPP. Despite the unlikelihood of recriticality, the possibility of it occurring cannot be discounted completely if a series of conditions were to occur simultaneously. The radiation produced by recriticality cannot pass through the concrete walls surrounding the reactor, which is beneficial for containment of immediate risk, but problematic for determining via standoff monitoring if recriticality has occurred until it is too late to take remedial action. Conversely, the radiation inside the reactor, amongst other extremes, is so intense that it presents another challenge as it can easily damage electronics and saturate radiation detectors.This project aims to develop and deploy a ruggedised, radiation-tolerant sensor system capable of real-time detection of subtle changes in the highly radioactive environment inside the stricken reactors to rapidly detect recriticality should it occur. Such technology is also applicable to the UK's nuclear decommissioning challenges and world leading research in fusion energy.