In the case of a severe accident in a core resulting from unprotected loss of flow (ULOF) or unprotected transient overpower, damage can propagate from subassembly to subassembly and produce a whole-core–scale molten pool. Because the core is not in its most reactive configuration, a massive collapse of the molten material could result in a rapid supercritical condition with release of a large amount of energy. However, timely and sufficient fuel relocation outside the core by dedicated means could prevent any risk of recriticality and accident escalation. Based on a reference 1500-MW(electric) sodium-cooled fast reactor design, this paper describes the main results obtained in evaluating the recriticality potential of the European Sodium Fast Reactor (ESFR) core and conditions for its elimination during a ULOF-type transient. This study has been carried out in the frame of the Collaborative Project on European Sodium Fast Reactor of the 7th Framework Programme Euratom. The numerical analyses carried out in the present work allow one to estimate the amount of fuel mass that has to be removed from the core in order to maintain it in subcritical conditions, preventing the formation of a critical pool. Requirements for successful application of this approach, in terms of the negative reactivity insertion rate by fuel relocation and timing of discharge from the core, are derived.