[en] This paper presents the main results from the application of the methodology of Risk Matrices in a hypothetical service / department of the Nuclear medicine that realize metabolic radiotherapy treatment and diagnostic studies with ¹³¹I and ⁹⁹ m Tc and ¹⁸F. We could identify major equipment failures and human errors that could potentially lead to a accident in practice. For each analyzed initiating events evaluated the frequency of occurrence, identified key existing defenses to avoid the accident and assessed the potential consequences of an accident if this comes to fruition. With this methodology we could identify which accident sequences increased risk and to propose means to reduce the risk in such cases. As a result of this work was developed the 'RMA Nuclear Medicine' computer tools that will apply this methodology in nuclear medicine services that need to do similar risk assessments