In this work, the use of natural resources was analyzed using a simplified methodology and assuming calculation conditions close to the real ones, to assess the sustainability of the nuclear source and the efficiency in the use of these resources. For the analysis of open fuel cycles, four reactors were selected, these being the Pressurized Water Reactor (PWR) and Pressurized Heavy Water Reactor (PHWR), two Generation II reactors commonly used until today, the advanced Generation III reactor AP1000 and the conceptual reactor AP-Th 1000. For closed fuel cycles, the variation of the utilization of the natural resource alongside with the variation of the conversion factor were evaluated, parameterized by the burnup. It was observed that the Generation II reactors use only 1% of the natural resources and, despite technological advances, the Generation III reactor did not show a significant increase in comparison to the former. Although the closed fuel cycle includes recycling the burnt fuel from thermal reactors, it exploits only about 10% of the resources. Major improvements are observed in Fast Breeder Reactors, being able to obtain a use of almost 100% with the increase of the burning and the minimization of losses. Although the feasibility of using thorium as a nuclear fuel has been proven, it would be better used in a closed cycle, as in the self-sustainable Liquid Fluoride Thorium Reactor (LFTR), a Generation IV reactor that can transform the nuclear energy in a sustainable and renewable source of energy.

Este trabalho discute a contribuição da energia nuclear para a complementação térmica do Sistema Interligado Nacional, as questões relacionadas com a usina Angra 3 em construção e analisa sua contribuição para a sustentabilidade do sistema elétrico. Neste trabalho avalia-se o valor estratégico da segurança energética provido pelas fontes termoelétricas e, em particular, pela alternativa nuclear. A análise de custo é baseada no custo marginal de operação. A análise de sustentabilidade considera 6 critérios: emissão de gases do efeito estufa, área imobilizada, consumo de matéria prima na forma de combustível, consumo de água, morbidade e fatalidades em acidentes. Esses critérios são considerados importantes pelos setores de energia, industrial e pela sociedade. Conclui-se que a energia nuclear na função de complementação térmica garante segurança energética, confiabilidade no fornecimento de energia, menor custo marginal e operação e maior contribuição para sustentabilidade.