Avaliação sistêmica de tolerância a falhas em sistemas de proteção de reatores nucleares

Abstract

O conceito de tolerância a falhas tornou-se importante nas últimas décadas na indústria nuclear devido à utilização de sistemas de Instrumentação e Controle (I&C) digitais. Uma falha é uma anomalia indesejada em um item ou sistema que pode levar a um estado inseguro e eventualmente gerar incidentes ou acidentes de consequências indesejáveis do ponto de vista socioambiental. Atualmente as soluções digitais são muito atraentes, não obstante, requererem avaliações de software quanto a tolerância a falhas. Nosso artigo pretende realizar uma investigação teórica de confiabilidade e taxa de falha, com base em um Diagrama de Blocos de Confiabilidade, em um sistema de proteção digital para reatores nucleares. Adicionalmente, discute sobre a necessidade de cultura de segurança nos segmentos de operação do reator, monitoramento e fiscalização para garantir que eventos acidentais indesejados sejam evitados.

Reliability and redundancy allocation analysis applied to a nuclear protection system

“…Figure 6: Reliability vs Time for cases: (1,2,3,5) and (1, 2 ,4, 6) Figure 7: Probability of Failure vs. Time for cases: (1,2,3,5) and (1, 2 ,4, 6) Figure 8: Failure rate vs. Time for cases: (1,2,3,5) and (1, 2 ,4, 6) Figure 9: Probability density function vs. Time for cases: (1,2,3,5) and (1, 2 ,4, 6) Table 3 shows the result of the failure rate of the simulations for each of the studied cases considering the operating times equal to one, one and a half and ten years. In this table it is possible to verify the influence of the value of the failure rate on reliability at the end of the simulated operating time.…”

“…Brazil is building, with national technology, two small nuclear reactors for propulsion and for the production of radioisotopes with thermal powers between 20 and 50 MW. These nuclear reactors fit more into the small modular reactor (SMR) class than the large nuclear power plant class [3]. Herder et al [4] reinforce the importance of probabilistic reliability analysis for the protection architecture of critical control systems in an industrial process.…”

“…The need to analyze RPS from the point of view of reliability to determine the likelihood of catastrophic failure depends on the security context [2]. This security context allows to evaluate the system's reliability performance through reliability allocation analysis to determine the overall reliability impact, increasing redundancies using equipment with higher failure rates [3]. Such an approach, while ensuring compliance with safety requirements, allows not only cost reduction, but also, in many situations, the feasibility of carrying out the project, since many countries have barriers to import systems, equipment and nuclear components.…”