This article presents a review of the French Institute for Radiological Protection and Nuclear Safety (IRSN) work regarding nuclear criticality accidents during the last 15 years. After the separation in 2002 of the French Atomic Energy Commission (CEA) and IPSN (the latest becoming IRSN), the IRSN nuclear criticality safety department had to develop its own skills and knowledge about criticality accidents.This article will present the background and the history of the research, with the legacy of the work performed by the CEA/IPSN team in Valduc. After reminding the framework for this field, dictated by the IRSN objectives and constraints, the strategy and the various achievements accomplished by IRSN in this field will be presented. In particular, the article will cover in detail the following “phases” that can be retrospectively drawn from this global work. Initially the appropriation and the analysis of past data and tools were necessary. Then the time for the first developments, the first experiments and the first collaborations came. Next, the close connection with the dosimetry field became apparent.Finally, the perspectives and the needs for this field will be presented. It will be emphasized the need for the use of experimental facilities that can study this hazard and the need for a strong national and international collaboration