A energia nuclear é um tema amplamente discutido em todo o mundo. O acidente nuclear de Chernobyl e o acidente radiológico de Goiânia contribuíram decisivamente para que a sociedade brasileira tivesse uma imagem negativa sobre o tema. A operação da usina de Angra 3, atualmente em obras, está vinculada à construção de um repositório para armazenar os rejeitos radioativos, o que provavelmente será explorado pelos opositores do setor nuclear. Um dos grandes desafios dos profissionais envolvidos nesse tipo de construção não é a engenharia em si, mas sim a aceitação pública do projeto, em razão do receio da sociedade sobre esse tema. O objetivo do estudo é levantar e apresentar experiências internacionais e nacionais sobre a aceitação pública de empreendimentos nucleares, com foco nos repositórios de rejeitos radioativos onde houve insucessos em razão de falhas nos processos de Comunicação Pública. É importante conhecer também os insucessos, de modo a não incorrer em erros semelhantes. Palavras chave: Energia nuclear. Rejeitos radioativos. Estratégias de Comunicação. Aceitação pública. Experiências internacionais.
Nuclear power plants (NPPs) are subjected to events such as equipment failures, human errors and common-cause failures, in an environment of complex maintenance, inspection and testing managements. These events will affect the reliability of safety-related systems, as well as the risk level of the plant. Reliability block diagram (RBD) is often used to analyze the effect of item failures on system availability, taking into account their physical arrangement in the system. Fault tree (FT) is a commonly used technique for analyzing risk and reliability in nuclear, aeronautical and chemical industries. It represents graphically the basic events that will cause an undesired top event. Loss of electrical power is one of the main events that influences safe operation of NPPs, as well as accident prevention and mitigation. In case of unavailability of offsite power, emergency diesel generators (EDGs) supply onsite electrical power. This paper carries out reliability analyses of EDGs of NPPs using both RBD and FT techniques. Each technique has its own advantages and disadvantages, allowing a variety of qualitative and quantitative analyses. Outcomes using these two techniques are compared for a typical NPP EDG system.
Probabilistic risk assessment (PRA), sometimes called probabilistic safety analysis, quantifies the risk of undesired events in industrial facilities. However, one of the weaknesses that undermines the credibility and usefulness of this technique is the uncertainty in PRA results. Fault tree analysis (FTA) and event tree analysis (ETA) are the most important PRA techniques for evaluating system reliabilities and likelihoods of accident scenarios. Uncertainties, as incompleteness and imprecision, are present in probabilities of undesired events and failure rate data. Furthermore, both FTA and ETA traditionally assume that events are independent, assumptions that are often unrealistic and introduce uncertainties in data and modeling when using FTA and ETA. This work explores uncertainty handling approaches for analyzing the fault trees and event trees (method of moments) as a way to overcome the challenges of PRA. Applications of the developed frameworks and approaches are explored in illustrative examples, where the probability distributions of the top event of fault trees are obtained through the propagation of uncertainties of the failure probabilities of basic events. The application of the method of moments to propagate uncertainty of log-normal distributions showed good agreement with results available in the literature using different methods.
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