Following the 2011 accident at the Fukushima Daiichi nuclear power plant, several high-priority actions were initiated by the NEA to address certain technical issues at nuclear power plants. One of these actions was to prepare a status report on spent fuel pools (SFPs) under loss-of-cooling and loss-of-coolant accident conditions, which was issued in 2015, providing an overview of both SFP accidents and mitigation strategies.

The present report is a follow up to this status report, documenting the results of a Phenomena Identification and Ranking Table (PIRT) exercise conducted by the NEA. This PIRT exercise identified SFP accident phenomena that are of high importance and yet are highly uncertain, thus highlighting their primary interest for further studies. The report recommends further support for existing experimental programmes and the establishment of a number of new programmes to focus, for example, on large-scale thermal-hydraulic experiments on the coolability of partly or completely uncovered spent-fuel assemblies and the investigation of spray cooling for uncovered spent-fuel assemblies in typical storage racks.