Strength check and fatigue analysis method for nuclear Class 1 pressure-bearing equipment based on ASME code

BackgroundIn the primary loop of a reactor, some pipelines are subject to the alternating scouring of hot and cold fluids for a long time. Moreover, local thermal stratification may occur, which further increases the thermal stress in the pipelines.PurposeThis study aims to avoid stress concentration and the resulting fatigue problems from potentially jeopardizing the safe operation of the reactor.MethodsA thermal-fluid-structure coupling analysis method for pipelines was established based on mature commercial software. The required strength check and fatigue analysis methods for nuclear Class 1 pressure-bearing equipment were obtained by combining the thermal-fluid-structure multi-physical field coupling method with the relevant standards and analysis process of ASME (American Society of Mechanical Engineers) code. In order to achieve batch calculations for multiple fatigue analysis locations, a fatigue analysis program was written in Python language. Based on this, the strength check and fatigue analysis were carried out for the pipeline system of a certain type of reactor.ResultsThe numerical results show that under the superposition of the current operating condition parameters and the number of occurrences, the stress classification results of the pipeline system meet the requirements of the code, and there will be no irreversible structural damage. In addition, the fatigue cumulative usage factors at the discontinuous positions of key structures are all less than 1.ConclusionsThere is no problem of stress and cumulative usage factor exceeding the limit in the pipeline structure of that analyzed reactor.