Autonomous Inspection for Responsive and Sustainable Nuclear Fuel Manufacture (AIRS-NFM)

Lead Research Organisation: Lancaster University
Department Name: Engineering

Abstract

Nuclear energy, derived from splitting the atom, is an important component of current UK electricity generation because it is low carbon and it is not affected by the weather. In order for the UK to reach its commitment for net-zero carbon dioxide emissions by 2050, nuclear power offers a way to offset the UK's previous reliance on electricity production by burning of coal and gas, whilst underpinning periods when renewable sources of electricity (off-shore wind and solar) are interrupted.

The fuel from which nuclear energy is derived currently is made from uranium. Fuel for all but one of the UK's existing nuclear power stations is manufactured at Westinghouse Springfields Fuels Ltd., near Preston. However, in the next 10 years, all of these power stations are scheduled to close. In order to offset this loss in low-carbon electricity, new reactor designs are being considered because the requirements of nuclear power have changed since the current generation of operating reactors were built in the 1960s-1980s: modular designs are favoured now in place of large reactors built at site, that will be easier and cheaper to build, and which provide more flexibility over the power that they provide. In the short-term, the UK is considering small modular reactors 'SMRs', that are smaller versions of a long-established design, and advanced modular reactors 'AMRs', which will operate at higher efficiencies at higher temperatures. The UK is well-placed to compete for the manufacture of the fuel for these new reactors because Springfields has more flexibility concerning the range in uranium composition open to it than many of its competitors, but it will need to be competitive on cost.

A principal opportunity to reduce the cost of nuclear fuel manufacture is to reduce the likelihood that fuel produced in the factory is not compliant with customer requirements. When this happens, the fuel has to be recycled through the process, unnecessary energy is consumed in recycling it, time is lost and waste is generated. In this research we shall study the uranium manufacturing process in the UK with the aim to investigate whether it can be made responsive to change in order to increase its efficiency and cost effectiveness. We have selected two examples where unexpected change can undermine compliance: uranium enrichment and pellet quality.

Uranium enrichment concerns the proportion of 235U present in the fuel; 235U is the isotope that is responsible for most of the energy that is generated. It is a key component of the fuel specification and, because enrichment is not constant across a reactor core, the enrichment of each pellet matters. Enrichment is influenced by changes in the feedstock (uranium hexafluoride) and by faults that might evolve in the manufacturing machinery. We will explore whether the most advanced ways of detecting gamma rays available today can be employed to yield a measurement of enrichment at various points in the process. We will explore whether these measurements can be used to constitute data to be used to adjust the process to avert a change in enrichment, so that the effect on the enrichment of a given pellet can be minimised and hence the need for a whole batch to be recycled is removed.

Pellet quality is premised on several factors: one is whether it is cracked or not. Pellets are checked by a variety of means including manually by experts at the end of the manufacturing process. At this stage microscopic cracks can be present occurring after the pellets are baked implying that they could be weakened beyond what is suitable for use in a reactor or that their thermal conductivity may not be uniform etc. We shall explore the use of hyperspectral and high-resolution imaging for this purpose, with the aim of deriving data for use in rendering the process responsive, so that, for example, an evolving flaw in a machine that is causing cracking can be removed before a whole batch is affected.

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