Five years after the Fukushima nuclear disaster, many robots have been developed to enter areas that are too radioactive for humans, in the event of a nuclear accident, measuring the level of radioactivity can be difficult and risky. A new detection system has been developed to come to the aid of plant operators and managers in certain emergency situations. While navigating in a radioactive environment and looking for sources.to facilitate this operation and make it safer, we have to assess the autonomy of this system, which is a robot operating in a radioactive environment based and to guarantee autonomy and intelligence for obstacle avoidance behavior, we will use a tool such as Fuzzy Logic (LF). In this article, we present an obstacle avoidance approach using this tool. The approach is validated by a virtual simulation on Matlab Simulink.