Pop up factory for SMR construction could transform nuclear project productivity

During his Spring Budget statement, chancellor Jeremy Hunt said that nuclear is a “critical source of cheap and reliable energy” that could help the UK meet its net zero obligations. The high cost and long process for building conventional nuclear power stations like EDF’s 3.26GW Hinkley Point C has made small modular reactors (SMRs) an attractive proposition.

SMRs have comparatively lower electricity generating capacity, but their smaller size and modular design means they can be brought online faster. In the Budget, Hunt announced that the first focus of new government body Great British Nuclear (GBN) is a competition to develop SMR projects, with winners announced by the end of the year. If SMRs are demonstrated to be viable, the government will co-fund the new technology.

A number of firms are vying to develop SMRs. Among them is Rolls-Royce SMR which is developing one and working with Bam Nuttall to improve the construction process. With its 470MW SMR power stations, Rolls-Royce aims to offer a product that is predominantly constructed using standard prefabricated components. It plans to build dedicated factories to produce them.

Bam Nuttall is one of the key partners in the UK SMR consortium, led by Rolls-Royce, which hopes to deliver an SMR by the early 2030s.

Rolls-Royce's 470MW SMRs will be predominantly constructed using standard prefabricated components

When Rolls-Royce had the initial conversations with Bam Nuttall about building the SMRs there was an emphasis on certainty of programme and fast delivery. Rolls-Royce established a target to construct each SMR within 500 days, which seemed impossible to achieve using traditional construction methods.

Bam Nuttall nuclear director John Prothero looked into factors which negatively affect productivity on conventional nuclear energy construction schemes to address them for the SMR project.

Weather conditions and moving labour, materials and machinery around the site were identified as key factors.

Site Factory

Bam Nuttall came up with the concept of a pop up facility dubbed Site Factory and has been working with consultant Expedition Engineering on its design. Site Factory is a 290m long, 130m wide and 63m tall steel superstructure, under which all the construction activities – including the bulk earthworks – takes place.

The superstructure is designed to be fully modular so it can be dismantled and re-used. An opaque, lightweight PVC membrane was selected for the exterior of the roof and sides.

Expedition Engineering senior director Ed McCann emphasises the fact that “it is not just a shed, it is a construction machine”. It incorporates a system comprising 30 overhead cranes across five gantries which are integrated into the roof structure.

It is not just a shed, it is a construction machine

The individual cranes would have a capacity between 25t and 100t, but the system has been designed to enable the use of several crane units to lift a single load of up to 300t.

“Having the sky full of hooks will allow us to have multiple work fronts throughout the whole process, enabling us to improve productivity significantly,” Prothero highlights.

McCann says that the superstructure could be completed in six months. The roof would be built at ground level, with the crane system mounted in it. Each of the legs would feature a jacking arrangement so the roof structure can be pushed upwards.

All construction activities will be carried out within the Site Factory (Credit: Bam Nuttall, Patent No. GB 2591785)

Double protection

Prothero points out that this concept protects the “environment from the project and the project from the environment” with minimal noise, air and water pollution and light spill. He says that this would be significant mitigation when submitting an environmental impact assessment supporting a Development Consent Order application.

The Site Factory would also minimise the impact of the weather on the construction process as work would take place indoors. An exercise carried out by Rolls-Royce and Bam using weather data revealed that bad weather can cost conventional nuclear build projects 109 days a year.

“I don’t think people really understand how much time we lose to poor weather in construction,” says McCann. “Programmes are continuously being re-engineered because we are not controlling the external environment.”

Another advantage of the Site Factory over nuclear power construction is the ease with which materials can be moved around. Distributing materials and components at the Site Factory using the overhead cranes means the process is unaffected by changes at ground level.

Having the sky full of hooks will allow us to have multiple work fronts throughout the whole process

The Site Factory also offers improved programme certainty. With the logistics of transporting and installing the SMR components and materials carefully planned, McCann says a level of precision similar to that of the manufacturing industry is possible.

He adds: “At the moment the unit of programming in construction is a week. If we want the benefits that they [manufacturing industry] get, we’ve got to get down to the minutes.”

When designing the Site Factory, Bam Nuttall and Expedition Engineering focused on the circular economy. The aim is for each Site Factory to have at least three life cycles, after which the steel components can be repurposed in the secondary market.

The carbon footprint of each factory and its operation over three life cycles has been estimated to be 21,000t.

“But you need to put that into the context that if we can take three years off a programme, millions of tonnes of carbon emissions [generated by non-renewable energy sources] would be offset with a nuclear power station,” says McCann.

De-risking

Bam Nuttall has secured the UK patent for the Site Factory concept and is now seeking them in other countries. Although it is new, the concept is based on tried and tested technologies, for example overhead cranes for tandem lifts.

“The innovation is in the way we put it all together, rather than any particular piece of kit that’s in there,” explains McCann.

He adds that the team would be able to further reduce project risk by carrying out digital rehearsals and, when appropriate, physical rehearsals of the different jobs.

Bam Nuttall and Expedition Engineering are currently developing all the requirements to deliver the SMR, among which are access, power supplies, heat and fume extraction. “Once that is finalised and agreed with Rolls-Royce, then we move to the detailed design phase,” Prothero says.

Whether the Site Factory concept progresses further than the design phase in the UK will depend on the outcome of the GBN’s competition. But the concept’s approach to industrialising the construction process for complex projects to boost productivity can be an inspiration for the construction industry.

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