FUEL & FUEL CYCLE | TECHNOLOGY
Samira Bostanchi
Ceramics technical consultant at Lucideon
Nicholas Barron
National Nuclear Laboratory Limited
David Pearmain
Head of field enhanced sintering at Lucideon
Flash sintering: life cycle applications
Flash sintering is a promising technology for producing nuclear fuel, but could also support the immobilisation of nuclear material to produce waste forms for disposal, as Samira Bostanchi, Nicholas Barron and David Pearmain explain
Below: The evolution of ceria pellets representing the progressive optimisation of flash sintering parameters throughout the Fast Reactor Fuels study
MANUFACTURING CERAMIC-BASED NUCLEAR FUELS and waste forms has often been an intensive process in both time and energy. Recent advances in manufacturing offer the potential to disrupt these established processes, providing economic and throughput advantages. Initial work suggests flash sintering can achieve this, by application and optimisation on surrogate (nuclear) materials. Advanced manufacturing techniques may produce a wide range of microstructures for re-use or disposal applications, depending on the requirements, but further development is still required to demonstrate and overcome challenges. Flash sintering (FS) is a field-assisted sintering technique, which uses direct application of an electric field to a pellet to shorten production timescales. Rapid heating takes place due to the direct dissipation of heat in the ceramic body, enabling lower furnace temperatures than in conventional sintering. In that way it promises tremendous energy reduction and enhanced throughput, and it has driven research on a wide range of materials with both economic and environmental motivations. FS was first reported in 2010 for yttria stabilised zirconia and it has since been applied to other ceramics. Recent work has extended this to nuclear fuels, mainly focusing on uranium dioxide or cerium dioxide, the latter as a surrogate.
FS has been shown to be effective in producing high- density uranium dioxide pellets, as a potential advanced manufacturing route to a common nuclear fuel. The remarkably fast rates of densification in uranium dioxide, and at lower firing temperatures than achievable by conventional sintering, has made it a promising candidate to study the densification of other nuclear ceramics. One such ceramic is mixed uranium-plutonium oxide (Mox) fuel. Recently published work has successfully applied FS to produce on oxide doped cerium oxide at significantly lower temperature and time. Due to the high neutron cross section of gadolinium it is often added to nuclear fuels to act as a burnable (neutron) absorber but it is also being investigated as a neutron poison for ceramic waste forms destined for disposal.
Sellafield mission and plutonium management The reprocessing of spent nuclear fuel will end on the Sellafield site shortly and its focus will shift exclusively to decommissioning of the existing nuclear facilities. A key component of the overall mission is managing
legacy nuclear materials. The UK holds the world’s largest separated civil plutonium inventory. Safely managing this inventory to a secure end point is a UK government priority, to avoid burdening future generations with security risks and proliferation sensitivities. The government aims to identify a solution that puts the UK’s civil plutonium beyond reach and to deliver nuclear cleanup/decommissioning. A recent analysis has highlighted the necessity to adopt a
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dual track approach to plutonium management because of the uncertainty in the capital and operational costs of Mox fuel manufacturing and plutonium immobilisation facilities, and the associated technical risks. There is a commitment
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