Estimativa de danos causados pela radiação ionizante em liga de aço com função estrutural em instalações nucleares utilizando simulação computacional

Abstract

The operation of nuclear facilities must satisfy the nuclear safety requirements. An analysis of the components of these facilities focus on the structural materials. The nuclear fuel burn will result in damage caused by ionizing radiation. Due to continuous operation, radiation damage will build up and may result on the manifestation of macroscopic radiation effects. Such effects may change the mechanical, physical and chemical properties of structural alloys. Thus, this work aims to understand the processes causing radiation damage to alloy steel during the operation of a nuclear facility, including the resulting degradation in material performance as this damage accumulates. A review was provided about the concepts associated to the microscopic characterization of alloy steels and their properties, as well as nuclear fission physics. The radiation damage and radiation effects were explained on the basis of these concepts and the references. The definition of the displacement cross-section was developed to calculate the displacement per atom (dpa) for irradiated materials. Investigations aiming sample irradiation to study changes in the mechanical properties of the selected alloy in CTEx research irradiator and in Argonauta reactor were conducted. Estimations for the dpa rates were calculated based on the ASTM-E693-23 standard for two scenarios at the Argonauta reactor. The low values observed were attributed to the limited neutron flux in that nuclear facility. The dpa calculation was also performed using the MCNP code to obtain the neutron spectrum on the inner wall of the Angra II reactor pressure vessel, estimating the dpa for the lifetime operation of this nuclear facility. The results obtained were considered in accordance with the references, thus validating the methodology applied.