Accidents and disasters in mining tailings reservoirs and dams are a growing global challenge, with high-magnitude environmental, social and economic implications, highlighting vulnerabilities in the risk management systems of large containment structures. In this context, through a prospective study of an environmental disaster scenario, this study analyzes the potential impacts resulting from the hypothetical rupture of the D4 dam, located in Caldas, Minas Gerais, Brazil. The present study highlighted the risks of nuclear contamination associated with the storage of uranium mining tailings. Through the integration of hydrological modeling, using the flood spot buffering procedure, and the application of the Economic Valuation of Environmental Damages (EVED) methodology, the potential environmental damages to vegetation, soil and water resources were estimated. The methodological adaptation of EVED allowed the quantification of the affected ecosystem services, resulting in an estimate of economic losses in the order of US$ 141,378,392.20. This value represents only the direct and indirect environmental costs of the potential loss of vegetation, soil and water resources, without considering the social, heritage and geopolitical impacts associated with the disaster. The D4 dam currently has a High Risk Category and High Associated Potential damages, with the possibility of releasing radioactive waste capable of causing persistent contamination for centuries, due to the half-life of the radionuclides present. The comparative analysis with historical disasters, such as Church Rock (USA) and Kyshtym (Russia), highlights the magnitude of the risk and the challenges for nuclear waste management in Brazil. The results highlight the urgent need to review safety protocols, assess the economic feasibility of remediation actions and adopt effective decommissioning technologies. This study advances the debate on nuclear safety by demonstrating the feasibility of integrated methods (hydrological modeling and EVED) to quantify risks in radioactive waste reservoirs, offering a replicable framework that alerts to the need for globally harmonized preventive protocols.