Safety: a proportionate approach in an uncertain application.

Fusion is inherently safer than fission due to the absence of nuclear chain reactions. However, operating fusion power plants will not be risk free. There will still be numerous hazards that will need careful management in order to safely build, operate and ultimately decommission a fusion power plant. Ensuring a robust safety demonstration that covers all radiological and non-radiological hazards is therefore vitally important for the future permissioning and consenting of fusion power plants. The safety case for the STEP prototype plant will be developed in line with a set of safety philosophies, safety functional requirements and design safety principles to ensure that the safety case production process is consistent and robust.This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.