Costain and Tetronics International have completed trials of a new system that promises to reduce the volume of intermediate level waste (ILW) from the nuclear industry by up to 90% compared with alternative approaches.
Reducing the volume of ILW helps to minimise the cost of packaging and storing it. Costain and Tetronics therefore collaborated in order to adapt and enhance Tetronics' existing plasma furnace technology to vitrify such wastes. Tetronics has 50 years of experience in supplying direct current plasma arc systems for a range of applications, with its latest variant drawing on Costain's considerable nuclear industry experience.
Investment in this project by Costain and Tetronics was supported by the UK's innovation agency, Innovate UK, with the Department of Energy and Climate Change and the Nuclear Decommissioning Authority (NDA) also contributing. Innovate UK, formerly known as the Technology Strategy Board, has a remit to fund, support and connect innovative businesses to accelerate sustainable economic growth.
The furnace operates at around 1000°C to 1400°C, taking between six and 12 hours to reduce waste to a glass-like substance. Tetronics built test facilities at Swindon over two years, with the trials taking two months. Organic and carbonaceous material in the ILW is vaporised and this waste gas is cleaned using a filtration process before being released. Any secondary waste collected from filtration is fed back into the reaction chamber of the furnace for vitrification. The inorganic material in the ILW, together with additives that reduce its melting point and increase fluidity, forms a pool of melted material in a water-cooled container.
The material is cooled to form a solid vitrified waste, which will be physically and chemically stable over thousands of years and which has demonstrated very low levels of leachability.
Reducing the volume of ILW would ease the burden on the UK's waste storage facilities and could mean considerable savings for the nuclear industry over the coming decades, with the added possibility of income through sale of the technology abroad. "We are now consulting with the nuclear industry on what the next steps should be," said Bryony Livesey, Costain's Head of Technology and Consultancy. "We're seeking to develop this further."