Demand for power continues to increase, and without enabling sufficient access to it, we run into serious economic, social and health problems, argues Prof Barry Marsden.
EDF Energy has recently announced the plant life extension of four of their Advanced Gas-Cooled Reactors – in Hartlepool, Heysham and Torness. Extending the operating lifetime of these reactors helps address concerns about the approaching energy supply gap, continues to support local economies and jobs, and helps meet the UK’s carbon emissions target. Whilst most welcome, it won’t be possible however for such extensions to continue indefinitely.
Yet, plans for new nuclear build are not coming to fruition any time soon. Hinkley Point C, the proposed new EDF nuclear reactor, is set to provide about 7% of the UK’s electricity and reduce carbon dioxide emissions by around 600 million tonnes over its 60-year lifespan. However, we are still a fair while off from seeing it contributing to supply, and speculation continues over the next steps along its journey as we await the news of a Final Investment Decision.
There has been a considerable passage of time since the last nuclear reactors were built in the UK. Construction of Dungeness B, currently the oldest nuclear reactor contributing to the grid, started operating back in 1965, and the most recent of the existing reactors, Sizewell B, came online over 20 years ago now. Since then, due in part to the advent of cheap gas, and also in response to populist anti-nuclear sentiment at a time before we even knew we should be concerned about carbon, the UK turned its back on nuclear power, investment dried up and energy problems continued stacking up for future generations to tackle. Our existing nuclear reactor fleet, currently supplying about a fifth of the UK’s electricity and a third of Scotland’s, won’t be able to produce electricity for as long as we might like, with two plants due to be retired in just seven years’ time and most of the remaining fleet closing over the space of a few short years thereafter. By 2030 only one, Sizewell B, is expected still to be operating.
This starts to put the country in a precarious position. This January the Institution of Mechanical Engineers reported that the UK is facing a 40-55% electricity supply gap by 2025. At the worst extreme we could start to see blackouts if strain on demand coincides with creaking coal plants breaking down out while the wind is not blowing. The margin between peak electricity demand and our maximum available generating capacity is getting narrower and narrower year on year. Lack of a reliable electricity supply has an impact on our health, economy and wellbeing. In modern times it is crucial to keep our heating working, our lights on and our homes and offices powered, as well as the given of maintaining power supply to essential services such as hospitals.
Whilst the incident might have passed many of us by, in November last year the National Grid had to take drastic action to keep the lights on, resorting to an emergency measure that pays large businesses, typically high energy users such as steelmakers, chemical plants and paper factories, to cut their electricity usage during peak demand. This step was taken as a result of the National Grid issuing a Notification of Inadequate System Margin (NISM). We’ve had to resort to other such notifications in the past, in 2012 and 2009. An additional measure of ‘last resort’ involves paying mothballed gas-fired power plants to turn themselves on if needs be.
Rather than falling back on creative (or is that desperate?) stop-gap measures, something is needed to reliably plug the gap whilst electricity demand continues to rise and our heavily polluting coal-powered stations are closed down. It is therefore welcome news to hear of the plant life extension of nuclear reactors, which have been reliably proving electricity over the decades, to bridge the energy gap..
The UK’s Advanced Gas-Cooled nuclear reactors (AGRs) have proved to be well designed and capable of exceeding their originally forecast operating lifetimes to help meet demand whilst we wait for new power stations to be constructed. EDF is undertaking a significant amount of work, both analytical and experimental, to ensure continued safe operation. One avenue of research for example is looking into possible plant modification to reduce the volume of water that can ingress into the reactor core in case of a boiler issue caused by loss of moderator mass.
A thorough understanding of nuclear graphite’s mechanical and structural properties is highly important for safe life extension, for instance understanding the effects of graphite aging in AGR moderator components. By virtue of its design the AGR benefits from inherent safety features, such as the graphite sleeves around each fuel assembly being replaced when a reactor is re-fuelled every few years which mitigates long-term aging issues. Graphite moderated reactors are particularly robust and components requiring maintenance can be detected with plenty of time to take action.
Future plant life extensions of existing reactors will be dependent on the approval of safety cases for each period of operation going forwards. A nuclear reactor in the UK is only licenced to extend operation for two to three years before a new safety case must be made to the Office for Nuclear Regulation (ONR). The University of Manchester’s Nuclear Graphite Research Group works closely with the ONR, providing research, expertise and independent advice in the review of such safety cases. We have four academic staff in the group, seven PDRAs and a number of PhD students carrying out experimental and analytical work on both unirradiated and irradiated graphite.
Nuclear power is essential for providing the secure, clean, reliable and dependable baseload power which is the bedrock of a balanced energy mix. Extending the operating lifetime of our current nuclear fleet helps keep energy challenges at bay for a few more years. Yet we need to look beyond to the bigger challenges on the horizon. Thankfully government has finally now recognised the importance of investment in nuclear R&D. Minimising emissions and maximising energy security are high on the agenda. Demand for power continues, and without enough access to it we run into serious problems. For now, we’ll strive to keep the lights on for as long as we can, whilst work continues on making future energy generation sources become a reality.
