Major technological risks are characterized by very weak probabilities of appearance coupled with consequences of very high gravity and ubiquity. Roles and responsibilities redistribution within organisation particularly impacts process pilots, on the strategic, organisational as functional levels. Cognitive, psychological and cultural biases intervene in their perception of such risks. From now on, these decision makers want to base their choices on a management system of risks as a whole but allowing apprehending them in differentiated ways. We present the characteristics of such a system.