Radiation imaging in operating reactors

16 October 2015

New imaging technology that can see the radiation fields emitted in an operating nuclear reactor has been developed by researchers in the UK. Inspired by cats' eyes, the camera technology could provide real-time monitoring of reactor cores.

Research led by Lancaster University with computing and electronics engineering firm Createc Limited shows that new imaging technology developed by the university can see high-intensity fast neutron and gamma-ray fields simultaneously. The research was funded by the Engineering and Physical Sciences Research Council. The results of this research - entitled "High-intensity power-resolved radiation imaging of an operational nuclear reactor" - was published on 9 October in Nature Communications.

The technology works by using the principle of back projection with a detector seated 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.

The imaging technology has been proven using the TRIGA mark II research reactor of the Atominstitut at the Vienna University of Technology, producing the first ever images of a functioning nuclear reactor using radiation emitted directly from the core as a result of the fission process.

Co-author of the research Malcolm Joyce, professor of nuclear engineering at Lancaster University, 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." However, he said the researchers have combined a portable imaging system with real-time radiation processing to enable photography of the radiation emitted by the reactor core.

The new imaging technology is the first of its type designed to be used outside of the reactor, is lightweight (about 20kg) and portable. Its lifespan will be longer than existing monitoring technologies - such as fission chambers and rhodium detector systems - which have to be located within the core of the reactor and are therefore subject to extremely harsh conditions, including high temperatures and radiation.

This means that the state of nuclear reactors could be monitored using the new technology in near real time, giving vital information on the state of the core, independent of installed instrumentation. It also potentially offers data on the efficiency of the fuel burn-up, providing safety and commercial information to operators. The technology could also be used to monitor research reactors.

Researched and written
by World Nuclear News