The reactor domes at Hinkley Point C are structures of complex geometry and construction constraints that required a highly engineered formwork solution. Each of the domes of the two units at the nuclear power station is comprised of an inner and outer layer. At Unit 1, the inner layer was completed at the end of 2025, and the pouring of the outer dome began at the start of 2026.
A flexible formwork system was demanded for a dome that curves in multiple directions simultaneously. VARIO formwork was selected for its adaptability, with 199 bespoke panels fabricated specifically for the dome works. Earlier transition sections from the vertical reactor walls up to level 13 incorporated RUNDFLEX circular wall formwork panels before progressing fully into the dome curvature.
Tie-Free Formwork Solution for Hinkley Point C Reactor Domes
The challenge extended well beyond geometry. The formwork had to operate approximately 45 m above ground level and support significant construction loads without relying on conventional tie systems. Dense reinforcement and post-tensioning ducts within the reactor structure meant traditional through-ties could not be used.
To overcome this, PERI’s engineers developed, from scratch, a unique, non-standard solution that combined several systems. The design incorporated SCS Starter Brace with 550 Strongbacks and load-bearing SB platforms suspended horizontally around the perimeter of the reactor building, combined with a single special component – 45-degree anchor adapters – for transferring the concrete loads back into the structure in the absence of ties. While SB platforms are typically used vertically for single-sided wall construction, at Hinkley Point C they were reconfigured to create platforms approximately 5 m wide to facilitate the curved concrete pour, around 5 m in height, with the special design of the platforms able to support the complex formwork, fresh concrete pressure, and heavy equipment and live loads of the operatives on site.
3D Digital Modelling and Engineering of PERI Formwork Systems
From an engineering perspective, the design required extensive modelling. Initial proposals began as 2D engineering drawings before progressing into 3D CAD and digital models to better visualise the interaction between the formwork, platforms, reinforcement, and surrounding structures. Because the configuration fell outside standard system parameters, PERI’s engineering team developed a full structural model to verify loads, connections, and anchor forces. Load paths were carefully designed so that forces transferred through steel RCS rails rather than through the timber deck, ensuring the system could safely resist the pressure of large concrete pours.
Optimising Formwork Installation and Efficiency at Hinkley Point C
The dense reinforcement within the reactor walls presented further constraints. Anchor positions had to be carefully coordinated around tightly spaced rebar grids and embedded components. During construction, slight deviations in anchor positioning required sections of the system to be redesigned on site. To avoid any issues when the formwork installation was mirrored on the reactor dome for Unit 2, PERI supported the site team with precise anchor placement and simplifying platform installation. Owing to the experience and learning curves of Unit 1, the entire formwork platform solution for the second unit was fully installed in under a fortnight.
Prefabrication also played a key role in efficiencies and speed of the installation. Many elements were assembled before delivery, reducing work at height and allowing platforms to be installed rapidly once on site.
Throughout the project, close collaboration between engineers at PERI UK and the construction team at Hinkley Point C meant challenges could be addressed quickly. The result is a unique formwork solution demonstrating the adaptability of PERI’s systems through detailed engineering and strong project integration on a scheme critical to the UK’s future infrastructure.
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