Sellafield Ltd has–in conjunction with the NDA and the Office for Nuclear Regulation–set a ‘strategic tolerance’ for completing key activities. It described this to us as the date “we really want to hit”, to ensure that the site is fully cleaned up by 2125. We explored the consequences of not achieving ‘strategic tolerances’ with particular reference to the ‘Waste Vitrification Plant’ and were told that there is no fundamental engineering reason why the ‘strategic tolerance’ of 2039 could not be extended in this case. However doing so would need careful consideration as it could affect planning assumptions made elsewhere on the site (such as those relating to Sellafield’s future requirement for sample analysis capabilities).20 The NDA recognises that devising measures which allow measurement and reporting of progress in the short term, while also providing confidence that Sellafield Ltd will achieve long–term outcomes, is challenging.21 It also told us that Sellafield Ltd was right to be “super–cautious” because of the extremely hazardous nature of its waste – though it was conscious that “this may sound like a load of excuses”.22 We sought to understand how the NDA would identify underperformance – particularly in light of the Office for Nuclear Regulation’s request that the NDA do more to hold Sellafield Ltd to account for delivery, safety and security.23 We note that Sellafield Ltd has not only missed most of its targets for retrieving and ‘vitrifying’ waste in recent years, it has generally fallen well short of the level of performance it deems ‘Acceptable’.24