Research progress on magnetic fluid sealing in nuclear irradiation environment

Magnetic fluid sealing (MFS), with advantages such as zero leakage and long service life, has become the core solution for dynamic seals in extreme environments like nuclear energy and aerospace. However, the high-energy irradiation environment where nuclear industry equipment is located is prone to cause the deterioration and alter the frictional behavior of MFS, which restricts its engineering application. Based on the author's years of research, this paper systematically reviews the irradiation evolution laws and related mechanisms of three core components, namely magnetic fluid (MF), permanent magnets, and lubricants, as well as their overall performance in MFS. Research shows that the agglomeration of magnetic particles (MPs), the desorption of surfactants, and the degradation of base carrier fluid are the core factors leading to the deterioration of MF performance. There are two explanations for the irradiation demagnetization of permanent magnets: the thermal spike effect and the defect pinning effect. Under irradiation, lubricants exhibit degradation behaviors such as abnormal viscosity, increased acid value, gas release, non-crystallization and oxidation. Meanwhile, the existing research has limitations such as mainly analyzing single components, lacking multi-phase coupling mechanisms, and insufficient correlation with overall sealing performance. Based on this, the research team of authors has invented a series of MFS that can withstand radiation dose up to 10MGy, and successfully applying them to nuclear industry equipment. In the future, efforts should be focused on breaking through in areas such as the coupling mechanism of component performance, long-term assessment of dynamic irradiation, modification of irradiation-resistant materials, and quantitative prediction models for frictional properties and sealing lifespan. This paper reveals the evolution mechanism of the tribological behavior of MFS system under nuclear irradiation conditions. A research framework for MFS in nuclear energy equipment has been established, providing theoretical references for material selection, structural optimization and reliability improvement of MFS.