The client have selected Assystem to deliver the concept design for the STEP fusion tokamak central column inboard shielding. The scope of work was to develop the design for the shield using integrated neutronics analysis, shielding calculations and thermal-structural analysis.  

Design for manufacture was a key challenge due to the novel shielding materials required to achieve the necessary level of shielding in a confined space. Assystem's design and analysis team worked together to optimise the balance between the shielding performance and ease-of-manufacture and assembly.

Development of the shielding required integration of active cooling channels to remove the significant heat generated during operation of the fusion device, while maintaining performance of the shielding material.

Assystem also designed a small-scale prototype shield for verification testing of the proposed concept design.


  • Integrated neutronics and thermal-structural analysis
  • Design by analysis and design optimisation
  • Concept design of radiation shielding
  • Detailed design of radiation shielding
  • Design of active cooling system
  • Design of small-scale test prototype

Client benefits

  • Design of effective shielding within the space constraints of the STEP fusion tokamak is a key feasibility and cost challenge for the project.
  • Assystem worked closely with the client to ensure the trade-offs between performance characteristics such as heat loss, neutron absorption and structural integrity were successfully optimised.
  • Development if an innovative approach to design for manufacture to allow easier assembly of the shield without creating ‘shine paths’ of lower shielding performance.

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