Sellafield is the UK’s most complex and challenging nuclear site. It holds around 85% of all the UK’s nuclear waste, much of which is stored in ageing facilities. Unlike modern nuclear facilities, many of the buildings at Sellafield were built with limited consideration of how they would ultimately be decommissioned. Cleaning up the site is a long-term endeavour, likely to last well into the next century. It is expected to cost £84 billion (in discounted prices), though this cost estimate is highly uncertain.

The Department for Energy Security & Net Zero (DESNZ) is responsible for setting policy on nuclear decommissioning in England. DESNZ sponsors the Nuclear Decommissioning Authority (NDA), which is one of its non-departmental public bodies. Sellafield Ltd, a wholly-owned subsidiary of the NDA, manages the site, spending £2.5 billion last year.  

The National Audit Office has reported regularly on the challenges the NDA faces at Sellafield, most recently in 2018. We concluded then that “work to reduce risk and high hazard at Sellafield has taken an encouraging turn for the better.” However, more work was required to measure, evaluate and communicate progress more effectively.  


This report will examine if the NDA and Sellafield are taking a sustainable approach to decommissioning, leading to permanent hazard reduction. Our report will look at whether they: 

  • are managing and prioritising the risks and hazards of the site effectively in the short and long term
  • have sustained the positive trend on the management of major projects we found in our 2018 report  
  • are deploying resources across the group effectively

NAO Team

Director: Charles Nancarrow
Audit Manager: Michael Slater