Nuclear energy has distinct advantages, but it also comes at a price which is difficult to mitigate: disposing of the leftover high-level waste products often warrants constructing geological repositories, dealing with obsolete design technologies and battling political delays.
While nuclear power represents the only energy-producing technology which fully costs dealing with waste into the product, safe methods for disposing of high-level radioactive waste include a sort of 'fear factor' element in the process.
The radioactivity of such waste diminishes with time, but the timeline is long. The process involves isolating or diluting waste to control the rate or concentration of any leftover materials. At least at this point, nearly all nuclear wastes are contained and managed using deep and permanent burial. High-level waste is the byproduct of essentially 'burning' uranium fuel inside a nuclear reactor, and it contains fission products and transuranic elements created in a reactor core. Highly radioactive and hot, it accounts for some 95% of the total radioactivity produced in the process of electricity generation.
In Europe as a whole, radioactive wastes amount to 81,000 cubic meters a per year. In the UK alone, that amount is some 5 million tons a year. In the UK, France, Germany, Japan and Russia all spent reactor fuel is reprocessed.
Sellafield is an enormous nuclear handling complex in the United Kingdom tasked with storing and mitigating nuclear waste from military and civil nuclear projects, and Sellafield Ltd. is the company created to carry out the clean-up work at all the Sellafield sites.
With material from many years of development on the sites, Sellafield deals with nuclear weapons waste and other parts built in an earlier, less sophisticated era. Now engineers on the project have found that 3D printing and scanning can create custom and often bespoke parts to take on the job.
"As a material scientist, 3D scanning and printing is the Holy Grail; the technology offers a huge amount of opportunity that we can exploit to continue the safe and accelerated clean up of Sellafield site," said Donna Connor, Head of Technical Capabilities at Sellafield Ltd. "The plants at Sellafield are unique, and many of them have been used for far in-excess of their original design specification. Our Magnox Reprocessing plant, for example, was originally designed to work for 20 years and now, 50 years later, it is still recycling spent nuclear fuel from power stations around the UK. With these older plants lots of parts are one-off designs, which makes it both expensive and time consuming to replace parts. If something has to be custom manufactured it could mean a plant is closed down until a part is replaced, and even if we can avoid closing the plant temporarily, we know for certain that the part will be expensive."
Connor says Sellafield has been at the cutting edge of nuclear technology from the outset. Home to the world's first nuclear power station in the 1950s, Sellafield were pioneers of the technology.
One 60-year-old solution, the Pile Fuel Storage Pond, is being decommissioned now, and a 40 ton stainless steel container has been modified to store the radioactive sludge from the pond to be encapsulated and treated.
"3D scanning is being used to design the new container lid," said Alistair Norwood, Head of Metrology at Sellafield. " The scan cost about $5000 versus the estimated $42000 cost of using a metrology rig. It was also carried out in a fraction of the normal 6 months taken to manufacture such a component using traditional tooling. This is just one example of the potential use of 3D scanning that could be applied at Sellafield – the opportunities are almost limitless. Anyone needing metal components, parts and one-offs could potentially benefit from 3D scanning. We're also exploring the world of 3D printing, and the PFSP has already used the technology to manufacture plant parts."
The lead mechanical engineer for Sellafield, Eduard Bordas, says he and his team saw early on how effective prototyping with 3D scanning can be.
"I was tasked with the job to re-use an existing container and to get a new lid designed with a filling port to allow the sludge to be metered into drums. None of the traditional metrology methods available gave us the same confidence that 3D scanning did," Bordas said. "3D scanning was simpler, cheaper and more accurate. It provided fit-for-purpose technology that we're adapting for the nuclear industry at Sellafield."
As redesigning an entire plant or parts thereof can be an enormous drain on resources and cost more than $3 million, Norwood says the cost savings generated by 3D printing will save hundreds of thousands of dollars at Sellafield.