Nuclear clean-up work at Sellafield faces an overspend of up to £913 million, according to a report from the National Audit Office (NAO).

Despite an improved performance from the Nuclear Decommissioning Authority (NDA) in delivering clean up projects at the hazardous nuclear site, the NAO said the organisation "still has a long way to go in decommissioning and cleaning up the site".

The report highlights that most major projects at Sellafield delivered their work to schedule and to budget in 2017-18, continuing a trend of improvement since 2014-15 following NAO's previous report in this area.

Yet, major projects are still predicted to deliver late and to cost more than the NDA originally expected. A total of nine major projects in 2015 which were in construction were anticipated to cost an additional 60% of their budget at design stage. Despite this now being reduced to 29% over budget, it is still forecasted to overspend by £913m.

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"The NAO has also found that evaluating overall performance at Sellafield is difficult due to a range of factors," the watchdog stated.

"For example, since the NAO last reported, the NDA has cancelled three projects after spending £586 million on them, saying it found a better way of delivering the work. Legacy ponds and silos programmes have also delivered less work than originally planned in three out of the past six years, but are still expected to reach critical milestones early.

"Evaluating overall performance is also complicated by the fact that the NDA has not yet been able to demonstrate how its current work leads to progress against the long-term mission.."

Overall, the NAO has recommended a review of the role, function and governance of the NDA, and that the NDA "improves its understanding and communication of progress at Sellafield, as well as the constraints to faster and further progress".

Amyas Morse, Head of the NAO, said the improvements in reducing risk at Sellafield are encouraging, "but the scale of the challenge is very great and the Department could be doing more to support the NDA through better governance and oversight of performance".

"The NDA, for its part, needs to do a better job of explaining what progress it has made and what it will achieve over the next 2 to 4 years so Parliament can hold it to account," he said.

"It might also help if there was less focus on the extraordinarily round terms of £120bn to be spent over 120 years, and more focus on what can be delivered in a more meaningful timescale, say within forty years, in terms of cleaning up this extremely dangerous nuclear legacy."

(LM/MH)