Three Mile Island, Chernobyl and Fukushima... These three accidents have led NPP operators worldwide to equip themselves with increasingly high-performance systems built to ever-stricter and higher standards, capable of managing their facility in post-accident situations. The use of ionizing radiation monitoring systems in the event of this type of accident is particularly critical to limit its scope of impact. Responding to these requirements is a genuine technological challenge in that the physical values (temperature, pressure, integrated dose, time, etc.) influencing the various hypotheses at play never cease to increase.