Radiation tolerant rapid criticality monitoring (REACTION)

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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.