Research on Design and Influence on Performance of Expansion Joint for High-temperature Sodium Pipe

Expansion joints are installed on the sodium pipelines of fast reactor power stations to absorb the displacement for thermal compensation. This can reduce the difficulty in the layout of pipelines, supports and hangers, effectively shorten the length of sodium pipelines and reduce the number of spring supports and hangers, thus realizing the compact layout of equipment, reducing the size of the process rooms and improving economic efficiency. To support the construction of the integrated fast reactor project, it is essential to carry out design research on the expansion joints of high-temperature sodium pipes. In accordance with relevant norms and standards, the formulaic approach was utilized to conduct design calculations regarding the key structural parameters of the expansion joints. Moreover, the effects of these key structural parameters on the performance characteristics of the expansion joints, including length, absorbed displacement, and stiffness, were comprehensively explored. The research outcomes disclose that the wall thickness, average radius of corrugations, and wave height of the expansion joints all exert diverse degrees of influence on the performance of the expansion joints. The computational results demonstrate that as the pitch of corrugations rises, the maximum axially absorbable displacement of the expansion joints also progressively augments. When the pitch of corrugations remains constant, an increment in wave height leads to an increase in the maximum axially absorbable displacement of the expansion joints. During the design process of expansion joints, a suitable elevation of wave height can be adopted to diminish the stiffness value. If the expansion joints absorb a greater displacement, the corresponding number of fatigue cycles will be reduced. Under the prerequisite of fulfilling the minimum fatigue life requirement, a larger absorbed displacement per unit corrugation expansion length results in a shorter total length of the expansion joints, thereby enhancing the manufacturing economic viability of the expansion joints. To sum up, the structural parameters of the expansion joints have a significant impact on their performance in terms of absorbed displacement, stiffness, fatigue life, and other aspects. In the design of expansion joints, by appropriately selecting structural parameters such as wave height and pitch of corrugations, the expansion joints can achieve enhanced economic efficiency while meeting the performance prerequisites.