Consortium appointed as delivery partner to UKAEA's STEP programme

STEP building

A consortium of fusion experts has been appointed by the UK Atomic Energy Authority as engineering delivery partner to its STEP Programme.

The consortium, led by Atkins and energy transition specialists Assystem, has been chosen to drive forward the Spherical Tokamak for Energy Production (STEP) programme as UKAEA seeks to demonstrate the commercial viability of fusion energy.

The delivery partner will play a critical role in STEP’s ambitions to design and build a commercial-scale prototype fusion energy plant by 2040 over the next two years.

Completing a concept design is one of two key tranche 1 objectives to achieve by 2024 that will enable UKAEA to proceed to future phases and meet its ambitious targets. 

Fusion technology has the potential to provide abundant, low-carbon energy – maintaining the UK’s net zero efforts in the long-term and underpinning future energy security.

The consortium is led by Atkins as prime contractor, alongside international engineering and digital services firm Assystem. 

Atkins and Assystem have a long history of successful collaboration across nuclear and fusion energy projects, including their work as architect-engineer for the international fusion energy project ITER, through the Engage consortium.

The STEP EDP consortium combines this world-leading expertise with specialist knowledge from partners across the supply chain: fusion In-Vessel Component materials technology and safety specialist Oxford Sigma; In Vessel Components and tritium specialists Kyoto Fusioneering and Ansaldo Nuclear. 

Combined, the consortium will bring more than 30 years’ experience in fusion delivery.

Christophe Junillon, managing director of Nuclear and Power EMEA for Atkins, said: “The commercialisation of fusion energy holds the key to unlocking an abundant source of safe, clean energy that will power a net zero future and the ambitious STEP programme positions the UK as a global leader in such highly complex projects. 

“A viable, investible concept design is central to UKAEA’s ambitions and Atkins is proud to extend our involvement in STEP’s development through this consortium.”

Simon Barber, UK managing director at Assystem, added “The STEP project is a fantastic opportunity for the UK to continue its leading role in the global race to deliver a commercially viable fusion power plant. 

“Assystem’s role in this delivery partner consortium for STEP builds on a long-term commitment to the development of UK fusion capability, harnessing a blend of UK skills, decades of experience on international fusion projects such as ITER and collaborating with UK fusion specialist SMEs.”

The consortium members have an established relationship with UKAEA.

Atkins was appointed power infrastructure partner to STEP in May 2022, in addition to its roles as commercial pathways partner, site selection and development partner, cost modelling partner, and developing STEP’s Integrated Plant Solution to define a conceptual mechanical handling and maintenance strategy. 

Assystem is currently delivering the STEP shielding design project, and has a wide range of in-vessel experience including pioneering the safe lithium breeder concept, and robotics and remote handling expertise under the LongOps programme. 

The consortium members have previously worked together to deliver wide-ranging projects released through UKAEA’s Engineering Design Services (EDS) and Embedded Engineering Resources (EER) frameworks, with both Atkins and Assystem holding Tier 1 positions.

Tristram Denton, head of commercial and programme development for STEP, said: “Fusion has great potential to deliver safe, sustainable, low carbon energy for generations to come, and STEP is leading the way. 

“It’s an ambitious programme operating at the forefront of science, technology and engineering. It’s clear we must make significant changes to address the effects of climate change, and STEP’s delivery partners will play a crucial role in our quest to making fusion a reality.”

If you would like to contact Karen McLauchlan about this, or any other story, please email