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A proposal to reuse the UK’s civil plutonium and recovered uranium stockpiles in thermal reactors has taken a step forward following the signing of an agreement with the Canadian government to enhance cooperation in civil nuclear energy.
Ontario-based Candu Energy is proposing to turn plutonium from legacy nuclear programmes into mixed oxide (MOX) pellets at a dedicated fabrication facility at Sellafield in Cumbria. The MOX fuel could then be used in four thermal reactors to produce up to 3GWe of power for sale in the electricity market.
Candu’s Canmox proposal has emerged as a front-runner among options under consideration by the Nuclear Decommissioning Authority (NDA), as it could deal with the entire stockpile, regardless of the grade or contamination.
The agreement is seen as a significant milestone that will strengthen the ties between the countries’ nuclear industries and establishes the means and processes by which a Canmox project could be adopted.
Preston Swafford, president of Candu Energy, said: “The arrangement galvanizes joint research and development, regulatory co-operation, technology transfer and investment into the UK nuclear sector and has the potential to unlock a powerful energy source for UK electricity consumers.”
Britain’s growing stockpile of civil separated plutonium waste has been mounting over many decades. More than 140 tonnes have been produced from a range of spent fuel types in a variety of facilities. The composition is therefore variable, with most of the material well characterised and of good quality, but with smaller portions contaminated or in the form of residues or mixed-oxide scraps.
The distinguishing feature of the Candu technology is the use of heavy water as a moderator that provides enhanced neutron efficiency, allowing for fuel flexibility. As a result, there are four distinct applications available or under development: natural uranium, recovered uranium, thorium and mixed-oxide fuel. It’s the MOX option that offers potential for the UK’s plutonium problem.
To achieve lifecycle management, Candu would deploy its proprietary Canmox process, in which plutonium and depleted uranium powder feedstock are combined into pellets to produce a fuel bundle that would be irradiated in new reactors. This approach would dilute, reuse and reduce the stockpile, safely and cost-effectively.
The reactor would be based on Candu’s Generation III 700MWe nuclear power plants, which are used around the world. The Enhanced Candu 6 (EC6) would be adapted to advanced fuel and MOX duty, with four reactors being built to provide 2.8GWe of baseload power for UK markets.
The Nuclear Decommissioning Authority has spent the past few months reviewing the potential of plutonium reuse in a Candu reactor. A position paper issued last year described the company’s solution as “clearly credible”. Overall implementation to first irradiation is predicted to be around 10-12 years, with reactors running on Canmox fuel for 30 years, providing low-carbon electricity to UK markets.
Discussions between Candu and the decommissioning authority continue, and a decision on whether to further progress the technology is expected by the end of the year.
This article has more details on the Canmox solution.