The formwork engineers engineers developed a bespoke, non-standard solution. The system allowed for the successful completion of the Unit 1 inner dome in late 2025 and has significantly accelerated works on the Unit 2 outer dome, where the entire platform solution was installed in under 14 days.
Peri UK 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.
The formwork had to operate approximately 45 m above ground level and support significant construction loads without relying on conventional tie systems. The reactor structure did not allow implementation of traditional through-ties, due to the interior airtight 6mm steel shell.
The 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.
SB platforms are typically used vertically for single-sided wall construction, at Hinkley Point C they were reconfigured to create platforms approximately 5m wide to facilitate the curved concrete pour, around 5m 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.
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. The Peri digital system was able to quickly produce kit lists for procurement on site.
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, the Peri UK engineering team supported the site team with precise anchor placement and simplifying platform installation.
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