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Flamanville: Nuclear learning curve

While the policy to adopt new nuclear electricity generation nudges slowly along in the UK, across the Channel a milestone has been reached on the first nuclear plant to be built in France for 15 years. Alexandra Wynne reports from Flamanville as it enters its final construction phase.

There is nothing small about the project to build the third nuclear plant at EdF’s Flamanville site in northern France. And the project’s most recent major milestone was typical of the scale of the scheme.

In July, EdF finished installing the massive steel dome on the new reactor building that will house France’s first European Pressurised water Reactor (EPR). That the dome is massive meant that the crane that lifted it in needed to be enormous.

And so it was. One of the most powerful and largest land cranes in the world was called in - the 200m tall Sarens SGC-120, known as Big Benny.

Ahead of the lift, the assembly of the vast crane was a major 10 week operation that required 250 lorry movements. All went well and the process to weld the circumference of the dome follows on to ensure the structure becomes leak-tight. To ensure the strength of the building, the dome will be clad in 7,000t of concrete.

“We have learnt a lot of lessons from the past - remember that this is the first time a nuclear power station has been built in France in a long time.”

Antoine Ménager, EdF

Its installation marks the point when the mega-scheme’s civil engineering works are 95% complete.

“Everybody involved in this demanding construction site is proud of what has been achieved to date,” says EdF group senior executive vice president - generation and engineering Hervé Machenaud.

“It marks an important milestone for the future.”

Few who know of the scheme would be surprised as to why this milestone is so welcome - the project has attracted attention as a result of rising costs and a slipping schedule.

Construction of Flamanville 3, adjacent to the existing Flamanville 1 and 2 plants, began in 2007. However, by July 2011 the schedule for the start of power generation was revised from 2012 to 2016 and costs were put at €6bn (£5.07bn). And in December last year EdF confirmed costs had risen by a further £1.69bn.

EdF explains that the cost increases were partly due to structural design issues and partly down to economic factors.

Pioneering scheme

But above all it is the project’s scale, and the fact that it is widely seen within EdF as a pioneering scheme, that has added to its complexity.

The firm’s role on the scheme is almost all-encompassing as “architect engineer”, with contractor Bouygues responsible for civil engineering works on the EPR construction.

And it is insistent that the project is a successful one.

“I’m confident in my worksite,” says EdF’s Flamanville construction manager for Antoine Ménager. “I can assure you we are proud.

“We have learnt a lot of lessons from the past - remember that this is the first time a nuclear power station has been built in France in a long time.”

He adds that as this is the first time that EdF has attempted to build the Areva-designed EPR anywhere, the project represents a “major leap” in the development of nuclear power technology. As a result, he refers to the entire scheme as “a launch process”.

“From the beginning, everything was underestimated in terms of time and cost/budget,” says Ménager. “It is very complex - and it is the first time this industrial process has been started in 20 years.”

Engineering issues

One of the key engineering issues centred on the pouring of concrete on site. Problems with cracking or poorly compacted concrete emerged. Alongside these, there had been instances of non-conformances with steel reinforcement bars not being arranged as indicated in drawings.

EdF says this was responsible for delays of “only several weeks” to resolve each of the problems and that quality control was strengthened as a result.

Ménager says that in Taishan, China where EdF is part of a team building two more EPRs, the team has already drawn all of the lessons from the construction - and difficulties - at Flamanville. As a result, it has taken “half the time”, according to Ménager.

The aim is that, all being well, if the UK new nuclear programme moves ahead, these lessons will inform the proposed development of EDF’s plan to build the UK’s first EPR at Hinkley Point C in Somerset.

Local employment

Work at the Flamanville EPR site commenced in December 2007.

Site personnel levels peaked at 3,200 people in 2012 (with 60% drawn from the surrounding region. External contractors employ 2,600 staff and EdF employs 600.

Cherbourg West job centre consultant Carole Poletto says the jobs being won by locals are “very technical” and include civil engineering, construction, formworkers and installers.

“The second challenge is what happens after the work site is complete,” she adds. The employees reaching the end of their work meet with their employers to interview locally, regionally and even nationally for work.

 

“As with most major projects, some problems with concreting were experienced during the construction of Flamanville 3 and rectified,” says EdF. “The lessons learned are being considered by the Hinkley Point C team and by the preferred civils bidder - Bouygues/Laing O’Rourke during the early contractor involvement phase of work.”

This learning, it adds, includes developing a “more integrated approach to design with construction contractor input so that the designer provides rebar more suited to the proposed construction sequence and location of construction joints”.

In addition, 3D analysis of complex areas of reinforcement will be undertaken and concrete testing has already commenced with the focus on developing mixes suitable for large pours with low heat of hydration and high durability.

Back at Flamanville, the civil engineering work has gained prominence, primarily because, up until the past few weeks, they remained on the critical path, but also because they are very visible, says Ménager.

The works are extensive. Principal construction components include the reactor building, a pumping station, turbine hall and the laboratory/workshop.

Concrete shell

A heavily steel-reinforced concrete shell has been designed to cover the most sensitive buildings at Flamanville - the reactor building, the spent fuel building, the control centre, and two of the four safeguard buildings that are designed in.

The principal function of the safeguard systems is to make the reactor safe in all circumstances. The safeguard systems have a triple function: to guarantee the control of the nuclear reaction and the power generated; to maintain the cooling of the reactor; and containment measures for radioactive substances in the reactor building in the event of an accident.

Protecting the reactor is an internal metal liner and a thick reinforced concrete liner with another, aircraft impact-proof and a reinforced concrete layer.

Each layer is extremely thick and must be capable of protecting the plant in the event of an earthquake. While the risk of a seismic event is considered low at Flamanville’s site in Normandy, it is an issue at the font of everyone’s mind since the devastating disaster at Fukushima in Japan where problems are still ongoing (News last week).

Ahead of the dome roof installation, workers installed a substantial temporary roof cover on the reactor building to enable works to continue.

This was important for the revised programme and helped keep the mammoth task moving. As a result, 95% of the total 400,000m3 concrete required is now in place, along with 1,500km of cables and 400km of pipeline.

Work is now entering its final phase. Some 46% of electrical and mechanical installation work has been completed and now that the dome has been in place, the heavy components of the nuclear steam supply system will be installed inside the reactor building over the next few months.

“This whole site is like a jigsaw puzzle - all the pieces have to come together at the end,” says Ménager

The EPR is scheduled to start producing electricity in 2016 and will have a capacity of 1,650 MW, enough to supply power to 1.5M people.
 

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