Desenvolvimento de estratégias para descomissionamento de reatores nucleares de pequeno porte no Brasil

Abstract

In recent years, Brazil has been committed to strengthening its regulatory framework and the Brazilian nuclear sector as part of its strategic vision to address future challenges in the energy sector. One of these challenges is the pursuit of sustainable and low- carbon solutions to achieve decarbonization goals and mitigate the impacts of climate change. In this context, the country envisions the possibility of investing in nuclear reactors as an efficient source of energy production. However, these reactors, upon reaching the end of their operational phase, whether due to the end of their life, early shutdown due to accidents, or the operator's decision, are decommissioned in a process that involves decontamination, dismantling of the structure, and proper management of generated radioactive waste. The decommissioning process consists of technical and administrative activities aimed at shutting down a nuclear facility, including the complete or partial removal of regulatory control. Due to the complexity involved in this process, the IAEA recommends that decommissioning of nuclear facilities be executed as an engineering project, with the difference being that it involves equipment and radioactive materials that need to be handled and controlled according to technical and regulatory prerequisites, ensuring they are in a condition that does not pose an unacceptable risk. The decommissioning project of a nuclear facility begins with the development of a preliminary decommissioning plan during the construction phase of the facility, which continues throughout the construction and operation phases. At the end of the facility's life, a final decommissioning plan is prepared and must be approved by the relevant regulatory authority before the commencement of decommissioning activities. Thus, decommissioning can take decades to plan and execute, in addition to requiring significant investment to achieve its objective. In this context, the decommissioning project must be carried out through a specific strategy, demonstrating its feasibility of implementation, aligned with the regulatory framework, and considering the technical, administrative, social, environmental, and economic considerations of the country in question. With the increase in nuclear activities envisaged in national policies and strategies, and considering recent regulatory changes, this work has developed a set of strategies for planning the decommissioning activities of small nuclear reactors during the construction phase. These well-planned and systematic strategies encompass the entire life cycle of the reactor, from its initial design phase to its decommissioning, and were based on a literature review on the subject and the use of risk assessment techniques described in the ABNT ISO/IEC 31010 standard. Additionally, they were based on international best practices and recommendations from the IAEA, aiming to guide the decommissioning of small nuclear reactors in Brazil.