On the reliability of construction structures at nuclear power plants

Introduction . This paper covers the classification and reliability of construction structures at nuclear power plants; the reliability of reinforced concrete elements of fire protection systems that prevent the spread of hazardous fire factors is assessed. Such structures were shown to be highly reliable in terms of normal operating loads, so their failures may not be considered in reliability analyses of safety systems and safety analyses of nuclear power plants. Aim . To demonstrate that the design requirements for nuclear power plant buildings and structures ensure a high level of reliability for their structural components, and therefore measures to protect these components from failure due to common causes are not required. Materials and methods. The reliability assessment of reinforced concrete structural elements in buildings and structures at nuclear power plants was performed in accordance with the recommendations of RB 100-15 using the two-moment method. Results . According to the study results and as required by clauses 1.2.12 and 1.2.15 of NP 001-15, elements of reinforced concrete building structures with a failure probability typically exceeding 10–3 may not be considered as an additional independent failure or initiating event in the analysis of design basis accidents. It is noted that measures to ensure the fire resistance of reinforced concrete structures in fires are aimed at protecting the reinforcement from exceeding the temperature at which its deformation and strength properties may change, which can lead to a loss of load-bearing capacity of reinforced concrete elements. Thus, while maintaining the properties of reinforcement, the reliability level of reinforced concrete elements is preserved, thus enabling structural failures to be disregarded in reliability analyses of fire protection systems. Conclusions . The high level of reliability of nuclear power plant structures, ensured by compliance with design standards, provides a basis for not considering their failures in system reliability and safety analyses.