Laser-mounted robots: the future of nuclear cleanup

Source: by Paul Day (Reuters)

Lasers strapped to autonomous aerial drones and free-moving robots may seem like science fiction but could soon be a reality for nuclear facility cleaning and decommissioning.

LaserClean’s hand held laser stripping rust from a metal surface (Source: LaserClean)

Generating electricity from nuclear fission can be a messy affair, leaving work surfaces and equipment encrusted with hard-to-shift radioactive materials that can take hundreds of hours of laborious grinding and/or chemical treatment to clean.

The result, aside from exhausted workers wielding loud and heavy equipment while stuck for weeks at a time in restrictive personal protection equipment, is a highly toxic runoff mix of cleaning materials, old paint and rust, and radioactive waste.

The original surface of any equipment or piece of infrastructure often remains too contaminated to recycle and must then be carefully disposed of, leaving tons of potentially recyclable material in the radioactive trash.

The jury is still out as to how far lasers can fully clean heavily contaminated, radioactive surfaces, but developers of the technology, who are already seeing strong demand from other heavy industries, claim the laser is the way forward for nuclear power cleanups.

“A laser can do things with a level of quality and adjustability that really cannot be achieved by any other method because they are so precise. Also, the process does not create secondary waste, which is an issue with most surface preparation or decontamination methods,” says Timothy Niemeier, Vice President of Adapt Laser Systems.

“You have a waste stream that consists of whatever medium that was used to grit-blast off coatings or by solvent cleaning and even when there’s water cleaning of radiological materials, you end up with copious amounts of liquid waste. By using only focused light, we reduce tremendously the rad waste which of course in many cases result in tremendous cost saving from the disposal side.”

Laser Cleaning
Source: AdaptLaser

Industrial magnifying glass

The laser’s nozzle shines a slim strip of unfocused light around 5 centimeters long onto the painted metal surface. By moving the nozzle, the strip is brought into focus like a point of light through a magnifying glass on a sunny day and the paint on the tray peels away and disintegrates to reveal the shiny metal surface below.

In less than five minutes, a tray the size of a large book has been completely stripped of decades-old red paint and is ready for reuse.

“When I think of all the surfaces in a nuclear plant and what it takes to clean – the grinding, the scrubbing, the waste – I can eliminate 90% of that,” says President of the Canadian startup LaserClean Ed Gledhill.

The LaserClean headquarters is a small workshop in an industrial park in Ajax, southern Ontario, and his four-man team has seen business go from strength to strength since he started three years ago.

“I get calls every day asking if I’m selling,” says Gledhill, pointing to the laser, the main body of which is around the size of a chest of drawers, the laser itself attached by long arm like a large vacuum cleaner.

Gledhill has signed an exclusive deal with a manufacturer in Italy and hopes to soon start expanding with franchises in five different locations.

LaserClean is a stone’s throw away from the Pickering and Darlington nuclear power plants and Gledhill says both operators have shown interest for laser cleaning for expander pipes and non-radioactive items though nothing official had been signed as yet.

“I know they’re looking at the website and what we’re doing because I can see the traffic and who’s visiting,” Gledhill says as one of his workers – a large man who goes by the name of ‘Moose’ – loads newly cleaned and gleaming molds for tractor tires onto the back of a truck.

“The trick is to get through to the people who need it and could use it.”

It is only a matter of time before nuclear power operators adopt the cleaning method officially, saving them millions of dollars, time, and worker frustration, he says. 

Contaminated dump trucks

While the laser, which is already widely used in other industries, is yet to become a staple in the nuclear cleanup community, studies have shown that its acceptance as an essential piece of the nuclear toolkit is little more than a regulatory ruling away.

Over 1000 nuclear reactors are expected to be decommissioned within the next 30 years. Each nuclear reactor could generate over 120,000 drums (roughly 24,000 cubic meters) of solid wastes. The cost of waste disposal in UK is estimated at £20,000/m3 ($25,000) for intermediate level wastes, according to the paper ‘The Potential Role of High-Power Lasers in Nuclear Decommissioning’ from Manchester University.

“Minimizing the waste volume is thus one of the important economical and environmental issues in nuclear decommissioning,” says the paper’s author Lin Li in the paper’s introduction.

The cost of waste is also calculated using weight, so stripping steel infrastructure and recycling it would be a crucial step in keeping weight, and so costs, down for the industry, says Adapt Laser Systems Niemeier.

In one case study conducted at Oak Ridge, laser ablation was used to decontaminate carbon-steel from 56 large dump truck beds that were being used to haul contaminated materials from sites around the decommissioning of K-25, a gaseous diffusion plant connected to the Manhattan Project.

The dump trucks had been leased to haul radioactive waste, but when it was time to return them, the leasing company would not accept the contaminated vehicles.

Decontamination of the dump trucks usually involves manual grinding of contaminated metal using heavy handheld power tools and required 200-man hours and two technicians to complete a single dump truck bed.

Adapt Laser and Philotechnics Ltd were brought in to show what the lasers could achieve instead.

One technician was able to clean the trucks using the laser ablation process in four hours and testing of the surfaces showed Alpha contamination had been fully removed and there was a significant reduction in Beta particles.

“If a laser can be used to clean tools, clean metals that would otherwise be rad waste, it’s going to enable the reuse of tools which would otherwise create a dose hazard to the personal using these tools. With the hazardous waste savings and the ability to recycle metals instead of burying them, they have residual value, instead of just cost,” says Niemeier.

And, with smaller, less powerful lasers – which, for a similar result, simply require more pass throughs – able to fit onto autonomous or remote controlled drones for hard-to-reach areas, laser-equipped robots working 24 hours a day seven days a week will soon be a reality.

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