As a result, existing studies on the economic impacts of a nuclear accident, and a fortiori on the risk of nuclear, can show differences of several orders of magnitude in terms of their outcomes. Most of the published work and quantitative analyses on this area have been carried out in the last decades at the PSI. In particular, PSI has been the main contributor to the comparative analysis of externalities due to severe accidents performed within the EU NEEDS project, New Ext and SECURE, which constitute to date the most comprehensive and detailed effort to characterise and quantify externalities in the energy sector.