Phenyl silicone rubber is primarily used in critical sealing systems in high-radiation environments within nuclear power plants.  Due to its excellent radiation resistance and high and low-temperature resistance, it has become an ideal sealing material for critical components such as personnel airlocks, equipment airlocks, and reactor cooling systems in the nuclear island.
I. Main Application Areas
Personnel and Equipment Airlock Sealing Systems
As the core material for O-ring seals, it is used in the sealing of personnel and equipment airlocks within the nuclear island, ensuring the integrity of the nuclear island.
Personnel airlocks have a diameter of approximately 2.9 meters, and equipment airlock heads have a diameter of up to 7 meters, requiring sealing materials to maintain reliable performance under extreme conditions.
In third-generation nuclear power technology, phenyl silicone rubber has gradually replaced traditional silicone rubber, becoming the preferred material for airlock sealing systems.
Nuclear Reactor Cooling System Sealing
Used in O-ring rubber seals for nuclear power reactor coolant pumps, meeting the requirement of maintaining an elastic modulus of no less than 80% of the original value at a high temperature of 150℃.
It needs to withstand a cumulative radiation dose of 10^6 Strict conditions requiring a volume expansion rate of no more than 5% after Gy radiation dose.
In LOCA (Loss-of-Coolant Accident) simulation tests, the material must undergo a one-year test under continuous high temperature, high pressure, and chemical spray environments.
Containment Penetration Seals
Used for sealing mechanical and electrical penetrations of the containment vessel to prevent the leakage of radioactive materials.
The containment vessel, as the last barrier against the release of radioactive materials, has sealing performance directly related to nuclear safety.
The phenyl silicone rubber sealing material needs to adapt to the complex interface between the containment steel liner (minimum wall thickness of 6 mm) and the penetrations.

II. Material Characteristics and Advantages
Radiation Resistance
High-phenyl silicone rubber (phenyl content above 30%) has excellent radiation resistance and is suitable for high-radiation environments such as nuclear power plants and reactors.
It can withstand high doses of γ-rays and β-rays, with a required cumulative radiation dose resistance of tens of millions of rads.
It maintains physical and chemical stability in a radiation environment, preventing seal failure.
Extreme Temperature Resistance
Low-phenyl silicone rubber maintains elasticity at extremely low temperatures of -70℃ to -100℃, suitable for nuclear power plants in extremely cold regions.
Medium-phenyl silicone rubber (phenyl content 15%-25%) has ablation resistance and flame resistance characteristics, and can maintain stable performance in high-temperature environments above 150℃.
At temperatures as low as -120℃. It remains elastic under various conditions, and the addition of heat-resistant additives allows it to adapt to a wider temperature range.
Comprehensive Performance Advantages:
Ablation resistance: Not easily damaged in high-temperature combustion environments, suitable for ablation-resistant components.
Chemical stability: Excellent resistance to radioactive materials and chemical corrosion.
Reliable sealing: Maintains structural integrity and sealing function under abnormal working conditions (such as short-term high temperature, pressure fluctuations, and seismic vibrations).
Long service life: Personnel access door seals require a service life of up to 24 months.

III. Technological Development and Application Trends
Material Upgrade Path:
Gradual transition from the early silicone rubber era to a new generation of material systems represented by ethylene propylene diene monomer (EPDM) rubber.
Current research focuses on the composite application of special modified EPDM rubber and phenyl silicone rubber to improve overall performance.
High-phenyl silicone rubber is increasingly used in critical sealing parts of nuclear islands due to its radiation resistance.
Future Development Trends:
With the development of fourth-generation nuclear energy systems and modular small reactor technology, the performance requirements for seals in terms of high temperature resistance, radiation resistance, and long service life will be further enhanced.
The research and development of new materials and processes will become a key focus of the industry, such as nanocomposite materials and new anti-radiation additive technologies.
Standard system improvement: Nuclear power sealing material standards will become more stringent, such as the "Technical Conditions for Graphite Gaskets for Nuclear Power Plants" (NB/T 20365-2015).
Progress in Domestic Application:
Domestic companies such as Anhui IOTA Silicone Oil Co., Ltd. have developed the IOTA series of phenyl silicone rubber products, which are applied to nuclear power plant sealing components.
Domestic companies such as Binzhou Shuangfeng Graphite Sealing Materials Co., Ltd. are promoting the localization of nuclear power sealing materials.
Domestically produced M5TM zirconium alloy cladding tubes have been successfully applied to the "Hualong One" nuclear power project, driving the upgrading of related sealing material technology.
The application of phenyl silicone rubber in nuclear power plant sealing components reflects the deep integration of materials science and nuclear energy safety. As nuclear energy technology develops towards higher safety, economy, and reliability, phenyl silicone rubber materials will continue to be optimized and upgraded, providing more reliable technical support for critical sealing systems in nuclear power plants.