Fluorosilicone oil exhibits significant material advantages in terms of chemical resistance in nuclear industry equipment, but its application has clear scenario boundaries and technical limitations.

Core Chemical Stability: Fluorosilicone oils (such as perfluorosilicone oil and methylfluorosilicone oil) significantly improve chemical inertness by introducing trifluoropropyl groups into the siloxane main chain. They can withstand strong acids, strong bases, organic solvents, oils, and complex media such as methanol-containing gasoline, maintaining structural stability in a wide temperature range of -60℃ to 250℃.  With a low surface tension of 20–25 mN/m, they possess excellent hydrophobic and oleophobic properties, effectively reducing media adhesion and penetration.

Radiation and Thermal Stability: The high bond energy of the Si–O bond in the fluorosilicone oil molecular structure gives it good radiation resistance, making it suitable for low to medium dose radiation environments. It exhibits good thermal oxidative stability during long-term use below 200℃, and the upper temperature limit can be increased to 250℃ by adding rare earth thermal stabilizers, meeting the high-temperature operating conditions of nuclear equipment auxiliary systems.

Typical Application Scenarios: Fluorosilicone oil is mainly used in the sealing and lubrication of non-core fluid circuits in the nuclear industry, such as:

Dynamic seals and lubricant bases for nuclear valves and pumps
Auxiliary sealing materials for instrument feedthroughs and flange gaskets
Vacuum pump lubricating oil (for handling active gases or solvent cleaning systems)
Its performance is highly correlated with that of fluorosilicone rubber, which has been proven to withstand non-polar media at -68℃ to 232℃, and has a low-temperature brittleness temperature as low as -89℃, making it suitable for sealing nuclear facilities in harsh cold environments.
Comparison with Perfluoropolyether (PFPE): Although fluorosilicone oil has excellent performance, its long-term stability in highly radioactive coolants (such as boric acid water and tritiated water) or strong oxidizing waste liquids lacks authoritative empirical evidence. In contrast, perfluoropolyether (PFPE), due to its molecular structure being entirely composed of C–F bonds, has superior radiation degradation resistance and chemical inertness, and is the preferred material recommended by the IAEA for nuclear main pump and valve seals. Fluorosilicone oil is more suitable as a cost-effective alternative for secondary systems with lower radiation doses.

Current technological limitations:  There are currently no publicly available technical standards from the IAEA or China National Nuclear Corporation that explicitly regulate the use of fluorosilicone oil in nuclear-grade equipment. Its application largely relies on internal company validation, lacking standardized lifespan assessment and irradiation aging data.  Therefore, it is not recommended for use in core areas such as reactor primary circuits, spent fuel pools, or high-level radioactive waste treatment systems.