[en] In January 1985 France faced a very cold period which had consequences on the operation of industrial installations, notably in the French nuclear plants where nearly twenty accidents were reported in relationship with these conditions. If, until this moment, frost was not considered as an external aggression such as earthquake or flooding, this situation resulted in the elaboration of document by EDF which defined general design rules for the protection against the cold which were notably applied to the Paluel reactors which were then in construction. The authors report the process of this elaboration. Thus, the authorisation for the loading of Paluel 4 has been the occasion for the launching of a reflection on the issue of extreme cold, and the authors comment the content of a report which has been elaborated between February and June 1986, and of other related documents. In a second part, they comment the return on experience of the nuclear reactors during the 1984-1985 period, and the late answers given by EDF during the period between June 1986 and summer 1987 as France faced again a cold period during the winter 1986-1987. In the third part which addresses the period between November 1987 and the beginning of 1988, they comment the content of a report which notably addressed an in-depth analysis of two incidents, discussions of practices and implemented measures, and also the content of a meeting of the permanent group of experts.