The consequences for the man and the environment of the discharges of nuclear facilities depend on the importance and the nature of the discharges, but also on the environment which receives them. Thus, the impact of a pollution, which is expressed in term of toxicity, risk or economic consequences, varies according to the characteristics of the environment and the use of this environment by the man. The radioecological sensitivity can be defined as the response of the environment to a radioactive pollution. For a determined discharge, the higher is the response, the more sensitive is the environment. If all the ecosystems appear sensitive, their sensitivity does not concern the same criteria and it is currently difficult to compare these criteria between them. The idea of the SENSIB project is to create a standardized tool which makes it possible to represent and to compare with the same scale the sensitivity of various ecosystems. The SENSIB project aims to develop both a methodology to calculate sensitivity indexes and a radioecological sensitivity scale usable for risk management.