Nuclear technologies and radiation have offered technological and scientific growth nowadays, but there is a frequent paradox in this. While these technologies substantially increase the quality of human life, they also produce radioactive waste, which, when not properly managed, can generate risks that threaten to harm the environment and health. As a result, in risk management of radioactive waste, decision-making processes need to be guided by a framework of principles, including the precautionary and preventive principles. For this reason, the present work proposes to develop a legal analysis on radioactive waste risk management using the principles of precaution and prevention. These principles have similarities, but it is the differences in their structure that deserve to be highlighted, which is discussed and exemplified throughout this work. Furthermore, national and international experience in environmental damage has taught us that an identification and assessment of risk is necessary, because if preventive measures are not taken radioactive waste can be dispersed and harm the environment. When it comes to assessing the risk of radioactive waste, one of the precautionary measures is the application of a conservative stance in modelling scenarios, as there are still uncertain risks. Therefore, comprehending the different circumstances surrounding precautionary and preventive measures and having effective information about risk is essential for successful risk management.