Following the evidence to life extension

Nuclear plant life extensions aren’t new, and they aren’t all that rare. While that may not be the most attention-grabbing opener, it is important context. It’s increasingly accepted by industry and governments that making the most of existing assets whilst it remains safe to do so is an excellent way to deliver clean, secure power to the grid for longer. Globally, around 100 reactors have already had their lives extended, including most of the UK’s fleet. 

Since EDF acquired the fleet in 2009 we have achieved 34 years’ worth of life extension across our Advanced Gas-cooled Reactor (AGR) stations delivering an extra 240TWh of low carbon electricity. That’s enough to power every UK home for two years and, when compared to gas, has avoided more than 83 million tonnes of CO2 from entering the atmosphere. 

While life extensions make sense, they are not a foregone conclusion and towards the latter stages of a station’s generating lifetime they may not be for very long. Before we make a decision, we have to be sure there is a robust technical safety case and also a good commercial case.

To do that we have harnessed today’s technology to improve our understanding of yesterday’s designs. Our reactors are made up of thousands of large graphite bricks which house the fuel and act as a moderator to help maintain the nuclear reaction. We have long known that the graphite would start to develop cracks as its ages, but these stations were designed with a slide rule and a calculator in the 1960s, so we didn’t have the ability to produce robust modelling outlining what that would look like and what impact it would have on operation. You hold more computing power in the palm of your hand when you scroll the internet on your phone, than was used during the design of these stations. 

That meant that back when the first graphite safety cases were put in place, they were exceptionally conservative. They still are, but since then there have been incredible developments in modelling methods, together with many years of real-life data gathered from the reactors, which have given us better visibility of the huge safety margins in place. This has allowed us to update our technical safety cases and increase cracking allowances with the confidence that we will still be able to shut our reactors down in extreme circumstances – like an earthquake larger than the UK has ever recorded.

Over the past couple of decades, we have worked with experts in the field – a range of specialist consultants and academics - to develop new ways to understand the cores. We have invested more than £300m in research and development to support our understanding of graphite aging. We also invest millions of pounds each year in inspecting our graphite cores to gather real life data to support our modelling. Next year this is expected to be in the region of £11m. 

Here are a few examples:

• Our work with Bristol University allowed us to create a quarter sized reactor to sit on a seismic shaking table and allow us to test different levels and combinations of core cracking under extreme conditions.
• We have been working with Quintessa for more than 20 years to develop statistical modelling to support our ability to forecast the condition of the core.
• Engineering experts at Glasgow University have developed forecasting software to help us understand changes to the graphite.
• We have worked with engineering consultancy, Amentum (formerly Jacobs), to create a life-size rig to demonstrate to the regulator the ability of the control rods to enter a channel distorted by an earthquake. It is just one of more than half a dozen physical rigs we have developed to validate our modelling of how different kinds of cracking might affect the cores.

What is absolutely certain is that we would not operate these reactors if we did not have confidence in their safety. Why on earth would we? And the independent regulator would not permit this either. Nuclear safety is our overriding priority and our approach to graphite aging is based on decades of accumulated knowledge and hard evidence to support this. We believe that this is the right approach to determining how long they continue to provide clean, secure electricity to the UK rather than anti-nuclear dogma or speculation.