Nuclear family: Hinkley Point C construction gets under way
Image credit: edf energy, getty images, science photo library
Construction of the UK’s first nuclear power station for over a quarter of a century is under way after many years of negotiations. So what is going on at Hinkley Point C? Can you still build a power station when you’ve forgotten how?
At this very moment beneath Somerset, hundreds of workers are boring a series of seven-metre wide tunnels that will channel millions of gallons of water to and from the Severn Estuary. Totalling 11km in length, they will be almost as long and as wide as the iconic Mont Blanc tunnel linking France and Italy.
Three massive boring machines and hundreds of workers will shift hundreds of thousands of tonnes of material and yet the project has barely received a mention in the press.
The tunnel’s creation has been overshadowed by its intended role of supplying cooling water to the Hinkley Point C power station – the biggest, and arguably most controversial, civil-engineering project of the new millennium.
After years of tortuous contract negotiations and public lobbying, on 29 September 2016 the government finally gave EDF and its Chinese partner China General Nuclear (CGN) the green light to begin building the new plant, thereby commencing almost a decade of work at the site.
Once operational, the two energy-efficient reactors at Hinkley will provide seven per cent of the UK’s energy needs. Each reactor will generate an impressive 1.6GW of electricity. And that’s just the start for the UK’s nuclear aspirations, as negotiations are under way for two additional reactors built by EDF at Sizewell C.
Progress, though, has not been easy. At almost £30bn, Greenpeace claims that the project will make the power station the most costly modern object built on Earth.
Very public concerns over the cost and long-term viability of the technology, as well as security issues, have cast a shadow the building of the UK’s first power station in over 30 years. Environmentalists and campaigners have questioned whether nuclear energy is, in a post Fukushima world, the right approach for the UK.
The reality is that the UK’s energy system is creaking. By 2035, all but one of the UK’s existing nuclear power stations will close – including the existing Hinkley Point B, which is due to be decommissioned in 2023.
This could leave the energy needs of the UK precariously balanced, with politicians claiming that renewables and green energy are currently unable to achieve economies of scale that will allow them to compete with fossil fuel technologies.
The government has made its choice. It’s time to meet the newest addition to the UK’s nuclear family.
Located just along the coast from the Somerset seaside resort of Burnham-on-Sea and ten miles from Bridgwater, Hinkley Point has been at the centre of the development of the UK’s strategy for nuclear power since a concerted effort to use this powerful new technology was made in the post‑war years.
The building of Hinkley Point C will make the site home to three power stations demonstrating the three generations of nuclear technology. The original Point A power plant was completed in 1965 and decommissioned in 2000, with the larger Hinkley Point B completed in 1976.
The scale of the construction at Hinkley is quite staggering. Over the course of the decade-long project, EDF estimates that more than 20,000 people will be involved in the site works. Over the entire supply chain stretching across Europe and the rest of the world, it could be many hundreds of thousands. When in operation, the plant will be the home to around 5,000 workers.
The first part of the process involves creating the earthworks and civil construction necessary to prepare the site. A fleet of massive machines supported by 1,7000 workers will help shift four million square metres of earth to prepare the site.
A temporary harbour and jetty will simultaneously be erected to allow ships to deposit the millions of tonnes of building materials required throughout the lifetime of the project. During the build, EDF estimates that more than three million tonnes of concrete will be needed – that’s around 12 times as much concrete as was used in building the new Wembley Stadium.
At the heart of the power plant construction are two separate islands: the nuclear island, the secure structure on which the reactor is built, and the conventional (or turbine) island, on which the steam turbines will be based to produce electricity. Building these is the first priority and will take around three to four years.
During this time trades will be fabricating and installing the infrastructure necessary for safe power genertation. Engineering partnership Cavendish Boccard estimates that each reactor will require around 70 miles of precision-engineered and fitted piping support systems. If that’s not enough, the team will need to install 35,000 supporting arrangements and 10,000 items of mechanical plant.
These systems will help to drive the station’s Arabelle steam turbines. The biggest steam turbines in the world, produced by GE Power, one of these units is longer than an A380 aeroplane, and can generate up to 1,770MW of electricity. They’re not cheap at around $1.9bn to manufacture, transport and fit, but with a claimed reliability of 99.96 per cent, are seen as a sound investment.
While undoubtedly a massive logistical challenge, the build of the essential infrastructure at the site is likely to be the easy bit. Sitting at the heart of Hinkley Point C will be two third-generation European Pressurised Reactors (EPRs). These reactors have a direct lineage from the first nuclear technologies, but they differ in two ways: size and safety.
In the EPR reactor, a water pressuriser keeps water at a steady 15.5MPa (around 100 times that of a domestic central heating system), which is heated to a temperature of around 300°C while being pressurised so it remains a liquid. This pressurised water is then passed through heat exchangers to a separate circuit which boils water at lower pressure. That water then turns to steam and is used to power turbines and thereby generate electricity.
The new reactors are larger than Pressurised Water Reactors (PWR) previously built in the UK, and this provides a number of benefits. The EPR has a larger core than previous reactors. As a result of the larger core and its surrounding neutron reflector, the maximum number of neutrons can be used to contribute to energy generation, making it more efficient.
As the pressurised water moves through the internal circuit, innovative engineering features like the new axial economiser ensure that the water passing through the steam generator transfers heat more effectively than in previous reactors.
These features improve the thermodynamic efficiency of the reactor by around 37 per cent when compared to current PWRs.
Size and efficiency mean that the EPR produces less of the harmful byproducts of nuclear power generation, cutting waste – which can take millions of years to become safe – by a third.
“The reactor has been designed to optimise the use of nuclear fuel and to minimise the production of long-lived high-level radioactive wastes,” claims Karim Bouamoud, HPC technical director at reactor builder Areva.
The reactor has also been designed to make use of mixed-oxide fuels, enabling it to be run on weapons-grade plutonium, which may otherwise be stored at an exorbitant cost.
Second-generation reactors like those at Hinkley B were built to withstand the sort of forces generated if a car or truck was crashed into the reactor. Engineers never considered that a hijacked plane might be used as a weapon, but the 11 September 2001 attacks on various targets in America changed that thinking.
Each of the reactors at Hinkley will be protected by a specially designed containment building. The structure has two walls: an inner pre-stressed concrete housing with a metallic liner, and an outer reinforced concrete shell. Each of these walls is a metre thick and has been stress-tested to withstand the impact of any plane currently operational.
The station has four “redundant, protected and geographically separated” safety systems in place. In the event of a problem with the cooling system, four independent diesel powered generators are ready to spring into action, providing the essential cooling power the core needs.
These are supported by two additional Station Blackout generators. Each generator is powerful enough to operate the safety system on its own, with Bouamoud estimating these would help cool the core for a week in the event of an accident or incident, hopefully long enough for action to be taken. Within the reactor itself, there are four cooling mechanisms to help cool the ‘decay heat’ (the continued release of heat into the atmosphere as a result of radioactive decay) for up to three years.
When an earthquake occurred more that 130km off the coast of Japan, it created a 15m-high tsunami that engulfed the site of the Fukushima nuclear power station, knocking out the core cooling technologies, and the station’s backup generators – leading to the meltdown of the station’s three cores.
At Hinkley Point C, a 760m-long, 13.5m-high sea wall will protect the plant from natural disasters. If water does break through, engineers are confident that the reactors and supporting infrastructure are watertight.
Natural disasters and terrorist attacks are not the only risks to take into account. Malicious attacks like those that took down the power grid in Ukraine in 2016 illustrate just how precarious our infrastructure can be, and is one of the main reasons for the hold up with Point C.
“The Hinkley reactor will be a key part of the national infrastructure for decades to come and hence any potential vulnerabilities should be under UK control.” states Professor Simon J Shepherd of the University of Bradford’s Interdisciplinary Research Centre in Cyber Security.
The EPR is the first reactor designed to be fully computerised during operation and incidents. Shepherd contends that the station and its critical systems “should be given a military level of protection.”
During the development phase, regulators questioned how independent the routine reactor control systems and the station’s security systems were, leading to delays and redesigns.
The securing of email communication and protection against common hacks is a relatively simple task. What’s more complicated is protecting the code itself. The reactor may have received regulatory approval, but the very real potential for ‘back doors’ to be built into the code is what has caused the delays. These weak points could potentially allow hackers to access the internal systems used to operate the power plant.
“This is why GCHQ is interested in scrutinising the Chinese software companies that are providing the control systems for the plant,” says Shepherd, adding that satisfying intelligence leads that the plant is safe for operation will involve the scrutiny of every line of computer code.
After an incredible 850,000 hours of testing, the reactor design to be used at Hinkley gained regulatory approval from the Office for Nuclear Regulation. On the drawing board, the reactor may work, but in the real world, things are a little different. “No EPR reactor has yet been built to time or budget: notes Neil C Hyatt, professor of nuclear materials chemistry at Sheffield University.
More optimistically, EDF engineering director Robert Pays says: “We’ve already built our Hinkley Point C EPRs in digital form. We know the position of every nut and bolt.”
EDF and Areva may be confident, but the building of a functioning EPR has been proved incredibly challenging. There are 277 PWR reactors globally. To date, there are currently no fully operation EPRs anywhere; projects at Olkiluoto 3 in Finland, Flamanville in France and Taishan in China are running over time and massively over budget.
“Many of the modern safety features mean that the design is very complex to engineer, and hence expensive to produce, which is reflected in the high strike price,” Hyatt explains.
To ensure they recoup their investment, EDF has negotiated a guaranteed ‘strike price’ – the amount of money the UK government guarantees to pay EDF for each MWh of electricity – of £92.50. While cheaper than many green alternatives, it makes power generated at Hinkley £27.50 more expensive per MWh than that generated by gas power plants, which has led to criticism from environmentalists and alternative energy campaigners.
The price is also guaranteed to rise in line with inflation, at a time when renewable energy costs are reducing.
“The whole approach to policy is wrong,” says Tom Burke, a former government advisor and chairman of environmental pressure group E3G. Describing the rapid progress in renewable energy and resulting cost reduction, Burke questions why the UK is investing in ‘unproven’ nuclear technology like the EPR. “Britain is repeating the catastrophe of previous generations,” he adds.
Burke points to financial problems within EDF and the spiraling costs of EPR projects across Europe as evidence for the economic and engineering failures of third-generation nuclear technologies.
The reality is that the UK government is committed to Hinkley C publicly and contractually, which means backing out is unlikely. However, as renewables reduce in cost and fourth-generation nuclear reactors developed by the Generation IV consortium become viable in the middle of the century, when it finally becomes operational in 2025 Hinkley Point C may find itself the only child in our nuclear family.
UK construction workers needed to build nuclear plant
The development of Hinkley Point C puts essential UK energy infrastructure – as well as contracts worth over £30bn – in the hands of French and Chinese engineers and developers. It has led to inevitable questions over whether the project could have been managed by UK engineers.
Andy Berry, vice principal at Bridgwater College, claims that, because the UK hasn’t built a nuclear power plant in more than 25 years, it has lost the requisite skills. “Many of our qualifications, skills and standards are either out of date, or don’t exist,” he says.
In order to get the plant up and running, these skills need to be revived. As part of the creation of the new power plant, Bridgwater College is helping to kick-start the UK’s nuclear renaissance.
French firm EDF itself has committed to creating over 1,000 apprenticeships over the course of the project, with suppliers adding many more to that number.
The college has seen the building of a new construction skills and engineering facility that will help train the thousands of construction workers needed for the site.
The Advanced Energy Skills Centre being built will help develop the skills and capacity of the UK nuclear engineering industry after a 20-year hiatus.
Together, suppliers, educators and partners need to work together to develop the UK’s nuclear capabilities. Indeed, the development of similar power stations across Europe could help develop a whole new area of expertise, potentially an opportunity for engineers throughout the continent.
Inside the European Pressurised Reactor
The European pressurised reactor (EPR) is a variant of the classic pressurised water reactor (PWR) that became the norm for nuclear power stations decades ago. A pressuriser ensures the water remains a liquid inside the core of the reactor even when heated to the normal maximum of 300°C.
Heated by the fission reactions in the rods that are lowered into the liquid while active, the water is pumped to a secondary system where it is passed through a heat exchanger to boil water in a separate reservoir, which creates the steam to drive two huge turbines.
The chain reaction is moderated by control rods. These are inserted into the core and are used to slow down or halt the process. Each fuel rod in the EPR core has a lifespan of 24 months.
The main aim of the EPR design was to improve safety compared to earlier PWR designs. The Hinkley reactor increases the number of redundant generators of the basic EPR design from four to six. Another tweak is the use of channels in the concrete base to spread the molten waste from an out-of-control core across a wider area.