Gamma camera: Re-imagining radiation monitoring

12 January 2016 (Last Updated June 9th, 2020 14:49)

Engineers at the Fukushima plant in Japan are using UK company Createc's N-Visage camera and imaging system to model radiation in 3D and improve safety as they work to decommission the facility's stricken reactors. Adam Leach profiles N-Visage and charts Createc's future plans for nuclear decommissioning technology.

Gamma camera: Re-imagining radiation monitoring

Createc

Detecting radiation is challenging; being able to get equipment that can measure radiation and track its spread - and all into a system small enough to operate in the inner core of a nuclear processing plant but big enough to gather valuable data - well that's an altogether different matter. For Createc, though, it was a challenge too good to pass up.

Spun out from an R&D group of civil nuclear engineering firm REACT in 2010, the company is seeking to apply its expertise in applied imaging and sensing technologies to develop new applications across a range of sectors. Its main focus to date, however, has been in the area of nuclear processing cells, developing technologies that can monitor and map radiation levels.

With its N-Visage Gamma imaging package, the company has managed to break the conventional constraints - where cameras were either too large to access the areas of most demand or too small to deliver detailed enough data - to deliver technology capable of mapping radiation in unchartered territories.

Having already had successful outings at Sellafield and Fukushima, the company hopes to roll out the technology across nuclear processing plants and also develop new applications for it, including an autonomous drone. So just what is the technology and where does the company see it going?

The N-Visage package

To deliver this new approach to imaging, the company has developed two separate, but complementary, components that when used together can deliver a detailed picture of where radiation levels are highest and even how they will change over time.

Providing the images for analyis is a 116mm-diameter gamma camera that weighs less than 10kg. Its small size means it can access most areas within plants and its lightness offers greater manoeuvrability. To gather the required imagery, the system uses a slot rather than a long cylinder to scan a full sphere of the gamma spectrum. By combining that with a laser scanner or photogrammetry technology to model areas that cannot otherwise be accessed, the camera can build up a full picture of the areas of interest.

"The system can calculate radiation levels against different methods of shielding or removing radioactive materials."

Complementing the camera is patented modelling software that takes dose readings from multiple locations within a specified area, drawn from a specific survey or built-in monitors, and then applies physics-based calculations to identify the lowest dose area from which to start out. At its more complex level, though, the system can calculate radiation levels against different methods of shielding or removing radioactive materials, offering an opportunity to weigh up the costs and benefits of alternative decommissioning methods.

Trialling the technology

Having conducted lab trials and tests on an early makeshift system, the company was invited to trial its first fully functional prototype at the Sellafield Nuclear Facility in Cumbria in the UK.

At the time, the area chosen to test the equipment was in the planning stages for decommissioning. While a prospective plan had already been developed, the capability of the system to show how different scenarios would pan out - by mapping and modelling how the radiation would be reduced at each stage - showed that a reassessment was in order.

"What we were able to do using N-Visage was simulate the way that process was probably going to pan out," says Dr Matt Mellor, managing director of Createc. "By doing that step-by-step process, we realised that you would have to do so many steps to get radiation levels down to manual working levels that it was actually no easier than just building robotic decommissioning equipment and doing it that way."

Developed with facilities such as Sellafield in mind, the technology's successful deployment was welcome but not surprising.

Taking radiation imaging to new heights

While the technology was developed for use in reprocessing plants, it has also proved useful to the clean-up efforts at the Fukushima Daiichi plant in Japan. Due to the damage resulting from the Tsunami in 2011, much of the access infrastructure at the plant has been severely damaged or destroyed, which has created a strong demand for an application capable of accessing hard-to-get-to areas and mapping radiation levels.

Explaining its work at the plant, Mellor says: "This system is both small enough and light enough to be attached to the end of a pole and put through a hole that you've drilled for the application or, as we did, attach it to a robot and drive it through the plant."

So far, the work by Createc to support operations at Fukushima has been restricted to the areas where radiation levels are low enough for the system to operate. But, due to the unique levels of radiation in the most damaged areas of the plant, the company is currently developing a new system capable of handling much harsher environments.

"This system is both small enough and light enough to be attached to the end of a pole and put through a hole that you've drilled"

"The target radiation levels in there are 10,000 times higher than what our current system can withstand, which is already about as high as it gets in the market," explains Mellor. For such a challenge, the trick will be to try and eliminate as many radiation sensitive components as possible, while also seeking to minimise exposure to those that can't be removed."

Future plans for nuclear imaging applications

Beyond its work at Sellafield and Fukushima, the company is focused on the Japanese, French and UK nuclear processing markets and also in the US where it has identified an opportunity for a smaller, cheaper N-Vision-lite type product. But it is also continuing to look at new areas in which to exploit the technology.

One application under development at the moment is a radiation mapping drone that is capable of flying indoors autonomously, or with very little human input, and constructing a 3D map of radiation levels. Discussing the development, Mellor says: "It is a fairly significant step towards a robotic radiation survey expert. It's able to act on its own or make its own proposals to be validated by a user in real time based on an understanding of the physics. It's quite a unique thing."

Also of interest to the team is exploring the scope of the technology to be used in the most active areas of nuclear processing plants - where the development of the next-gen Fukushima focused model will no doubt prove useful - and also in enabling better monitoring of performance of vitrification plants - where nuclear waste is encapsulated in glass to produce benign waste products.

With successful outings notched up at home in Sellafield and away in the clean-up campaign at Fukushima, the N-Vision gamma imaging technology is proving to be a valuable tool to the nuclear industry in understanding where radiation levels are at their highest and where they will spread. In removing the trade-off between size and quality of date, the technology has cast off one of the most significant limiting factors in this area. It will be interesting to see what innovations lie in store for the future.