New research - “High-intensity power-resolved radiation imaging of an operational nuclear reactor” - led by Lancaster University with Createc Ltd. and published today by Nature Communications provides evidence that new imaging technology developed by the University can see high-intensity ‘fast-neutron’ and ‘gamma-ray’ fields simultaneously.
This means that the state of nuclear reactors – as found in nuclear power stations – could be monitored in near real time, giving vital information on the state of the nuclear core, independent of installed instrumentation. It also potentially offers data on the efficiency of the fuel burn-up, providing highly valuable safety and commercial information to operators. The technology also has potential to monitor small medical isotope reactors.
As the new imaging technology is, very importantly, the first of its type designed to be used outside of the reactor, and is lightweight and portable – weighing around 20kg and able to fit inside a suitcase – it has a longer lifespan than existing monitoring technologies, which have to be based within the core of the reactor and are therefore subject to extremely harsh conditions, including high temperatures and radiation. It can also be deployed quickly and easily in remote locations, particularly important when dealing with the aftermath of emergency situations.
In the case of nuclear accidents, such as at Fukushima Daiichi in 2011, existing reactor core-based systems are likely to be destroyed – resulting in emergency procedures that have to be implemented without critical information on the source, location and direction of radiation emissions. In addition, existing external imaging technologies can take months to provide data. This lack of real-time data in emergency situations can complicate the ease with which the state of a plant is assessed. This new technology would be vital in helping speed up the response in the event of a disaster.
Malcolm Joyce, Professor of Nuclear Engineering at Lancaster University and co-author of the research, said: “It’s surprisingly difficult to obtain a radiation-based image of an operating reactor from outside of the core because there is understandably a lot of shielding and the space in which to install the instrumentation can be very limited. Jonathan Beaumont, the leading researcher on the project, has combined a portable imaging system developed by our partners at Createc with real-time radiation processing developed at Lancaster to enable photography of the radiation emitted by the reactor.”
The technology works by using the principle of back projection with a detector sat behind a slit-shaped collimator, similar to the slit pupils of cats. This exploits the property of radiation to travel in straight lines before it interacts with the environment. The rate of detections and ‘view’ of the detector from different positions and angles enables the source of the radiation to be determined.
The use of cat-like slits also enables the technology to be used in high-intensity radiation activity levels as the design prevents the detector from becoming saturated by limiting the view of the sensor to only part of the environment. This design has not been used previously to detect fast neutrons emitted by nuclear reactors, and enables a quick and effective assessment utilising only a single standard detector.
The imaging technology was proven using a TRIGA mark II research reactor producing the first ever images of a functioning nuclear reactor using radiation emitted directly from the core as a result of the fission process. Other partners involved in the research, which was funded by the Engineering and Physical Sciences Research Council (EPSRC), include the Atominstitut at the Vienna University of Technology and Hybrid Instruments Ltd.
Currently 11 per cent of electricity worldwide is generated by nuclear reactors. There are 435 reactors in operation with another 71 under construction. Most of these are light-water power reactors, or medical reactors, which could adopt this new technology. This new imaging technology would provide insights throughout the life-span of reactors, post-defueling and also throughout decommissioning.