Nuclear energy generation in the UK

With energy industry regulator Ofgem and the UK government setting their sights squarely on boosting renewables like wind, solar, biomass and hydropower, readers may wonder about the state of the nation’s nuclear power industry and the future of nuclear energy in the UK.

If your only knowledge of nuclear energy comes from the recent Chernobyl miniseries (or even The Simpsons), you may need a helping hand separating the facts from the fiction when it comes to nuclear energy and its place in the UK energy market. In this post, we’ll endeavour to provide a greater understanding of the past, present and future of British nuclear energy.

Nuclear energy in the UK: How does it work?

Ever since its inception over half a century ago, nuclear energy has been enshrouded by mystery. Indeed, when many of us think about nuclear power, our thoughts turn to the glowing green monstrosities of yesteryear’s science fiction. And while the nuclear power industry has incredibly stringent safety measures in place today, the spectre of 1986’s Chernobyl disaster and other high-profile incidents at home and overseas linger in our collective memories.

In order to set aside the myths, the misconceptions and the patently ridiculous, we need to understand how nuclear energy works. At the heart of every nuclear energy plant is a nuclear reactor. This is responsible for transforming radioactive materials like uranium into the energy we use in our homes and businesses.

Nuclear reactors explained

Nuclear work by initiating and sustaining a reaction that causes radioactive material to take in neutrons, splitting its component atoms. When the atom is split, it produces huge quantities of neutrons and emits an enormous amount of radiation.

The radiation from this sustained nuclear chain reaction is then used to boil large quantities of water to create pressurised steam. This steam is fed into a turbine to generate electricity.

However, while these nuclear reactions can generate enormous amounts of energy, they’re also extremely hard to keep under control.

Therefore, while the principles behind sustained nuclear reaction boiling water and driving steam turbines is the same in all nuclear reactors, different variants use different mechanisms to control the chain reaction.

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Gas-cooled reactors (AGR)

Most of the nuclear reactors in the UK are gas-cooled or AGR reactors. These use inert gases such as CO2 or helium to cool keep the reactor core at a stable temperature. A heat exchanger runs through the reactor, turning water into the steam that powers the turbine. Graphite moderators are also used to slow down neutron particles emitted during the reaction. This enables them to generate heat, making the reactor more energy-efficient. Control rods are used to absorb neutrons in order to slow down or shut off the chain reaction altogether.

Pressurized water reactors (PWR)

While there are fewer PWR reactors in the UK, this is the most common kind of reactor worldwide. Instead of using gas like AGR systems, PWR reactors use a flow of pressurised water to cool the reactor. This results in the conduction of heat to a steam generation vessel that is then connected to the turbine.

Unlike AGR reactors, the steam generator vessel does not pass through the reactor core itself. Instead, a primary water loop is fed through the steam generator vessel, outside of the core. The water in this primary loop acts as the reaction moderator, ensuring the reactor’s safety. As the temperature of the water increases, the molecules move further apart, thereby reducing the risk of neutron collisions and preventing the heat within the reactor core from building to dangerous levels.

High power channel-type reactors (RBMK)

This reactor type borrows elements from both AGR and PWR designs. It uses both water and graphite rods to keep the reactor cool. This system was developed in the Soviet Union, and the ill-fated Chernobyl power plant used this type of reactor.

However, as the tragic incident showed us, this system did not feature sufficient redundancy and safety systems. And although this was mitigated significantly in the years that followed, RBMK reactors would continue to be seen as somewhat risky.

In the mix: How much of the UK’s energy fuel mix is nuclear?

According to data from Ofgem, nuclear energy makes up just 11.9 of our energy fuel mix. You can see the full energy fuel mix stats in the table below:

Although the UK has a significant nuclear energy infrastructure, the presence of nuclear energy in the UK energy fuel mix is eclipsed by that of France (74.1%), Russia (35%), Germany (12.4%), and the USA (21%). This year’s figures show a sharp decrease in nuclear power over the past 20 years, with nuclear energy providing 21.16% of the UK’s energy fuel mix in Q1 of 2000.

As wind power becomes an increasingly cheaper, more renewable and far less risky and expensive way to generate energy, we can expect nuclear power’s presence to shrink in the coming years.

However, this creates its own set of problems as nuclear power plants are notoriously difficult, dangerous and expensive to decommission.

Nuclear power stations in the UK: A history

Since the dawning of the atomic age in the 1950s, the UK has seen a number of power stations come and go over the years.

To get a snapshot of the UK’s nuclear power stations over the years, we’ve compiled this timeline that shows the rise and arguable fall of nuclear power in the UK:

• 1954: The United Kingdom Atomic Energy Authority (UKAEA) was established to oversee and the development and deployment of nuclear energy in the UK. This body still exists to this day.
• 1956: Calder Hall in Cumbira, the world’s first nuclear power station, is opened by Queen Elizabeth II. The site costs £35 million to build and boasts four reactors and a total capacity of 194 Megawatts (MW). The facility will remain operational until 2003.
• 1957: The oil crisis in the Suez canal precipitates an ambitious new building program for nuclear power plants. Over the next 8 years, the UK’s nuclear capacity grow to around 5,000–6,000MW.
• 1959: Chapelcross, Scotland’s first nuclear power plant begins production in Dumfries. With a capacity of 196MW it will remain operational for more than 4 decades.
• 1962: Two more nuclear plants begin construction adding 500 MW of capacity to the grid. Bradwell in Essex and Berkeley in Gloucester.
• 1964: The advent of gas-cooled (AGR) reactors marks a shift towards technology focused exclusively on electricity production rather than military applications.
• 1965-1968: Production begins on new power plants including Hinkley Point, Trawsfynydd, Dungeness, and Sizewell. In 1966, the first prototype fast breeder reactor (the first kind of reactor to produce more fuel than it uses) is commissioned in Dounraey, Scotland.
• 1979: Energy secretary David Howell announces the building of 10 new pressurized water (PWR) reactors.
• 1988: As the 1980s draw to a close, some of the UK’s legacy nuclear power plants are decommissioned, including Berkeley 2 which was shut down after 26 years of operation.
• 1995: Sizewell B, the UK’s last fully-functional nuclear power plant (to date) to be built and connected to the grid, is completed after an arduous 7 year construction period. With a capacity of 1,188MW, this PWR reactor is expected to continue production until 2035.
• 2010: After a lengthy hiatus, the new generation of 8 nuclear power plants is announced by the government, including Hinkley Point C (still under construction).

How many nuclear power stations are now on the UK map?

At the time of writing, there are currently 7 active nuclear power points on the UK map, all of which are located on the UK coastline. This is because the because the reactors need large bodies of water to provide the cooling necessary to keep waste heat discharge at a manageable level.

At each site there are anywhere between one and four nuclear reactors. Moving from south west to north east, the active nuclear power plants remaining in England are as follows:

• Hinkley Point in Somerset
• Dungeness in Sussex
• Sizewell in Suffolk
• Heysham in Lancashire
• Hartlepool in County Durham

The two remaining sites in Scotland are:

• Torness in Dunbar
• Hunterston in West Kilbride

Why are nuclear power plants decommissioned?

Between 2003 and 2015, some eleven nuclear power plants have been decommissioned. These include Calder Hall, the first ever nuclear power plant in the UK, and the last two nuclear power plants in Wales, Wylfa and Trawsfynydd.

The decommissioning of the Calder Hall site demonstrates just how much work goes in to decommissioning a nuclear power station. As well as deactivating the mechanisms for generating energy, the nuclear fuels themselves need to be disposed of safely. Radioactive materials and waste need to be entombed and the site needs to be monitored for decades before it can be used again.

The whole process takes around 90 years to complete.

Nuclear power plants are decommissioned for all sorts of reasons. Sometimes they are becoming increasingly risky to operate, their infrastructures start to fail or they simply cease to be profitable. But the expense, risk and timeline associated with the decommissioning of unsafe or unprofitable nuclear power stations is an important factor in the shrinking presence of nuclear energy in the UK’s energy fuel mix.

Who are the main nuclear energy providers?

In the UK, all 7 active nuclear power stations are owned and managed by EDF Energy, which in turn is majority-owned by the French Government. All nuclear installations in the UK are, however, overseen by the Office for Nuclear Regulation (ONR).

How safe are UK nuclear power plants?

Many nuclear bodies both at home and overseas are quick to state that the UK’s nuclear power plants are safer than ever. And as Hinkley Point promises to demonstrate (when its construction is finally finished), the new generation of nuclear power plants will be safer and generate more affordable energy than ever before.

In all fairness, the current generation of nuclear reactors are much safer and more stable than their counterparts that precipitated tragedies at Chernobyl and Fukushima. Furthermore, the human error that led to these tragedies is far less likely to be repeated now that we have the benefit of hindsight, history and more stringent safety regulations.

Today’s rectors also have a range of safety functions that can contain damage far more efficiently than their older counterparts with "core catcher" systems isolating and containing the reactor core in the event of a meltdown.

Passive cooling systems also ensure that the rector’s safety features are never dependent on access to external energy. Furthermore, the new generation of reactors are able to use fuel much more efficiently. Not only does this create fewer potential heating problems, it also allows us to extend the usable lifetime of our uranium reserves.

High profile UK nuclear energy accidents and incidents

The nuclear industry has been vocal about how there has not been a major nuclear incident in the UK since 1957. However, there are a number of nuclear accidents and incidents in the UK that, while not as impactful as Chernobyl, have cast doubt over the long-term safety and viability of nuclear energy in the UK. Especially in an era where we have so many renewable alternatives.

Below we’ve compiled a timeline of high profile nuclear energy accidents and incidents in the UK:

• 1957: A fire at the Windscale site leads to the release of radiation. Ranked 5/7 on the International Nuclear Event Scale (INES) it remains the most serious nuclear incident in UK history with an estimated 240 cancer fatalities occurring as a result.
• 1967: Nuclear fuel gets stuck in a reactor channel at the now-decommissioned Chapelcross nuclear power station. The magnesium aluminium alloy (Magnox) cladding fails to contain the radiation emitted by the fuel melt.
• 1978: Another incident at Chapelcross resulted in one fatality. However, no details were leaked to the press.
• 2001: At Chapelcross again, nuclear fuel is accidentally lifted out of its shielding, exposing workers to radiation.
• 2005: At Sellafield, a processing plant for domestic and international nuclear waste, 80,000 litres of radioactive waste leaked out of a pipe into a secondary containment vessel. Thankfully, no radioactivity was released into the surrounding environment.
• 2007: While decommissioning Sizewell A power station, a contractor noticed a leak responsible for dumping 151,500 litres of irradiated water into the North Sea. The damage would have been far worse had the leak not been found by chance. However, this is still classified as a serious event.
• 2009-2012: Dungeness B experiences a boiler annexe fire, contributing to long-term shutdowns. Thankfully, however, the nuclear reactor itself was not affected.

The environmental impact of nuclear reactors and waste

As we can see, generating nuclear energy has certain inherent risks. When something goes awry, it can result in the leakage of radiation that can be devastating to environments and communities.

However, even when things are working perfectly fine, there’s still a risk of considerable environmental damage. Like most methods of power generation, nuclear energy produces certain waste by products that need to be disposed of properly in order to prevent environmental damage. The vast majority of this waste contains very low levels of radiation. However, some nuclear waste is highly radioactive, emitting radiation that could last for centuries.

Nuclear waste is broken down into the following categories:

Low-level nuclear waste

This comes from all kinds of sites. Not just nuclear power stations but hospital radiology departments, and scientific research centres. Waste in this category might be made up of discarded work clothing or tools. While it makes up around 90% of nuclear waste, it accounts for around 1% of total radioactivity. However, it needs to be treated as hazardous waste as a precautionary measure to prevent any risk, however remote, of radioactive contamination.

Intermediate-level radioactive waste

This kind of waste represents around 7% of total nuclear waste and requires effective shielding to be put in place as it demonstrates above-average levels of radioactive emissions. This kind of waste could be made up of chemicals, cladding and insulation materials, as well as materials that are collected during the process decommissioning.

Because transporting this waste off-site brings with it associated risks (and costs), this kind of waste is usually buried in shallow trenches on-site.

High-level nuclear waste

This form of waste usually originates in nuclear reactors and makes up the final 3% of all nuclear waste in the UK.

Processed nuclear fuels are the most common example of this. Once the reactor’s fuel rods have reached the end of their life cycle, they need to be extracted from the reactor core and disposed of safely. This kind of high-level nuclear waste contains unstable radioactive compounds that emit harmful radiation. In some cases, it can take tens of thousands of years for this radiation to die off naturally. As well as proper sealing and responsible disposal, this type of nuclear waste also requires active cooling as it generates high levels of heat. This increases its toxicity and moreover makes it a potential fire hazard.

You can find out more about nuclear waste and how it’s disposed of by checking out the World Nuclear website.

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While nuclear energy can be seen as something of a mixed blessing, it is nonetheless an important part of a safe and renewable energy industry that eschews the burning of fossil fuels. Different suppliers have different percentages of nuclear energy in their energy fuel mix. Choosing the right tariff and supplier means voting with your wallet for a greener future. Not to mention saving a lot of money.

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Looking to find out more information about energy production? Great! Check out these related articles

1. Where does electricity come from
2. Renewable energy sources
3. Coal energy

FAQ

Is nuclear power a renewable energy?

While nuclear energy is much lower carbon than burning fossil fuels to generate energy, it is not renewable in the same way that wind, solar, bio and hydroelectricity are. It still requires finite resources in the form of nuclear fuels. And while it can produce far more energy than most renewables on the market, it also generates waste that is potentially hazardous to the environment if not disposed of properly.

How many nuclear plants are there in the UK?

At the time of writing, there are 7 active nuclear power plants in operation across the UK. However, there is an 8th on the horizon. Hinkley Point C is currently underway and is running approximately 2 years behind schedule. It is owned by EDF Energy, one of the "Big 6" energy suppliers and majority-owned by the French government. When completed, the site promises to represent the next generation of nuclear energy in the UK.

How much of UK energy is nuclear?

As of the first quarter of 2020, nuclear energy represents 11.9% of our overall energy mix. This is a significant reduction from previous years, and a reduction of 9.26% when compared to the first quarter of 2000.

Is British Nuclear Fuels Limited (BNFL) owned by the UK government?

The British Nuclear Fuels company was a government entity that previously owned all of the UK’s nuclear power sites and infrastructure. However, nuclear energy in the UK was privatised in 1984, some 6 years prior to the rest of the energy industry’s privatisation in 1990. This gave rise to the privately owned British Nuclear Fuels Limited or BNFL.