'Cat's-eye' camera can monitor fuel burn-up in nuclear reactors

A portable camera based on the function of a cat’s eye, which can create images of the radiation emitted by a nuclear reactor from outside the core, has been developed by researchers in the UK.

The camera, which can image high-intensity “fast-neutrons” and gamma-rays simultaneously, could monitor the burn-up of fuel in nuclear power plants, to ensure they are operating efficiently. It could also allow clean-up crews to remotely detect the source and location of radiation within a reactor, in the event of a nuclear disaster like that at Fukushima Daiichi in 2011.

The camera, which was developed at Lancaster University by research student Jonathan Beaumont and Malcolm Joyce, a professor of nuclear engineering, was published in the journal Nature Communications.

Conventional nuclear reactor detectors, which are installed inside the core itself and are therefore subject to extremely harsh conditions, do not tend to survive for the lifetime of a power plant. But the devices can be difficult to reach in order to check or replace, according to Joyce. “You would typically have to switch off the reactor in order to gain access to the detectors,” he said.

In the event of an accident such as that at Fukushima, these detectors are likely to be destroyed completely, he said.

The cat’s eye camera, which weighs just 20 kilograms and can fit inside a suitcase, could be carried to the site and operated remotely, generating images in near real-time.

The camera, developed in collaboration with Cumbria-based nuclear technology company Createc, consists of a detector plate located behind a collimator - a type of filter - which has a slit-shaped hole similar to a cat’s pupils. This limits the amount of radiation that can hit the detector.

Without the slit collimator, radiation emitted from the reactor would hit the detector from all directions, said Joyce. “If you use a traditional collimator, which is essentially just a pipe, then it can be swamped,” he said. “It would be like looking at the sun.”

What’s more, the slit shape makes it quicker and easier to find the “sweet spot” for imaging the level and direction of radiation inside the core.

That is because conventional tube-shaped collimators must be scanned across every position along the horizontal and vertical axis in order to find the radiation source. In contrast, the slit-shaped collimator allows operators to look along a line across the core, said Joyce.

“So even if we’re not on the axis with the radiation, we can get an impression of where the optimum position on the other axis is, and then we are able to quickly move to that position,” he said.

This can be done by rotating the head of the device, meaning the camera does not need much space in which to operate, he added.