In the nuclear industry, material failure is not an option. Elastomers — used in seals, gaskets, O-rings, and insulation — must maintain integrity under constant exposure to ionizing radiation, high temperatures, and chemically aggressive environments.
Unlike pressure or heat alone, radiation damages elastomers at the molecular level, breaking down polymer chains and causing embrittlement, swelling, and loss of elasticity.
This article explores how different radiation-resistant elastomers behave in nuclear environments, and what design engineers must consider when specifying sealing solutions for nuclear reactors, containment systems, and radiological facilities.
Challenges of Nuclear Environments for Elastomers
- Ionizing radiation:
- Gamma rays, neutron flux, and beta particles cause chain scission in polymers, leading to hardening or softening depending on structure.
- Thermal stress:
- Continuous temperatures between 80°C and 200°C, often in dry, oxygenated environments.
- Chemical exposure:
- Steam, borated water, radioactive byproducts, nitrogen oxides, hydrogen peroxide, etc.
- Longevity requirements:
- Elastomers may be expected to perform for 20+ years in containment areas.
Key Properties of Radiation Resistant Elastomers
- Radiation tolerance (measured in Mrad or kGy)
- Low outgassing and chemical resistance
- Retention of compression set and tensile strength
- Resistance to thermal aging
Material Comparison Table
Property: Radiation Resistance (Mrad)
- EPDM: 10–30
- FKM (e.g. Viton™): 20–40
- Silicone (VMQ): 2–5
- Perfluoroelastomers (FFKM): 40–60+
Property: Temperature Range (°C)
- EPDM: –50 to +150
- FKM (e.g. Viton™): –20 to +200
- Silicone (VMQ): –60 to +200
- Perfluoroelastomers (FFKM): –20 to +320
Property: Chemical Resistance
- EPDM: Excellent (steam)
- FKM (e.g. Viton™): Excellent (acids/oils)
- Silicone (VMQ): Moderate
- Perfluoroelastomers (FFKM): Excellent (universal)
Property: Compression Set Resistance
- EPDM: Good
- FKM (e.g. Viton™): Excellent
- Silicone (VMQ): Fair
- Perfluoroelastomers (FFKM): Excellent
Property: Cost
- EPDM: Low
- FKM (e.g. Viton™): Medium
- Silicone (VMQ): Low
- Perfluoroelastomers (FFKM): High
Property: Typical Use in Nuclear Plants
- EPDM: Seals, gaskets, hoses
- FKM (e.g. Viton™): Valves, pumps, O-rings
- Silicone (VMQ): Non-critical applications
- Perfluoroelastomers (FFKM): Reactor core instrumentation
Application Areas in Nuclear Facilities
- Reactor containment seals (door gaskets, pressure flanges)
- Pump and valve shaft seals
- Cable and connector boots
- Sensor housings and feedthroughs
- Radiological waste containers
Material Engineering Notes
- Crosslink density is key: elastomers with tightly crosslinked structures resist chain scission more effectively.
- Additives (e.g., carbon black) can enhance radiation resistance.
- Peroxide-cured compounds typically outperform sulfur-cured ones in radiation environments.
Conclusions
The choice of radiation resistant elastomers directly affects the safety and reliability of nuclear systems. While FKMand FFKM are leaders in performance, EPDM remains cost-effective and widely used, especially where steam resistance is essential.
Engineers must evaluate trade-offs between cost, performance, and longevity—especially in critical applications.
At Siliconiton, we work with our partners to co-design elastomeric solutions tailored to the harshest radiation environments, from power plants to waste management systems.
