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In cutting-edge fields such as nuclear medicine, aviation, and aerospace, polymer materials face severe challenges owing to long-term exposure to extreme radiation environments. These environments impose stringent requirements on the service reliability of materials, which makes it imperative to improve the radiation resistance and aging resistance of polymer materials. To this end, amorphous boron powder (B) was used to prepare amorphous boron powder/silicone rubber (B/SR) composites because of the possible radical-scavenging characteristics of the empty orbitals present on the outer layer of amorphous boron powder. The impact of B on the radiation resistance of silicone rubber was investigated through systematic studies on the changes in the mechanical, thermal, and crosslink density properties of the material before and after irradiation. The experimental findings demonstrated that, at an absorbed dose of 200 kGy, the retention rate of elongation at break of B/SR0.3 sample can be maintained at (49.4±3.1)%, whereas pure SR is only (24.7±2.7)%. The initial breakdown temperature of irradiated silicone rubber composites raised from 454.9 °C to 472.8 °C by adding 0.3 parts of B, which significantly enhanced its thermal stability in radiation environments. To visually demonstrate the changes in the internal radicals of the silicone rubber composite during irradiation, this study used a UV lamp-electron paramagnetic resonance (UV-EPR) spectrometer for real-time monitoring and revealed that B could effectively eliminate the free radicals generated in the silicone rubber composite during the irradiation process. This study provides an effective strategy to improve the radiation resistance of silicone rubber composites and lays a solid foundation for the development of novel radiation-resistant polymer materials.

In some reactors, ammonia and its radiolytic product (H2) are used to scavenge the oxidizing species (H2O2, O2, and •OH). A reducing chemical environment is thus created and the pH of the coolant is regulated simultaneously. In the present study, the radiolytic behaviors of deoxygenated ammonia solution were studied in the γ-ray field. The impacts of N2 pressure, gas-liquid volume ratio, and temperature on deoxygenated ammonia solution radiolysis were investigated. The pH and the concentrations of residual ammonia, H2, and nitrogen oxides (NO2- and NO3-) were analyzed. The results revealed that the variation of N2 pressure (0.5~5.0 MPa) and gas-liquid volume ratio had no influence on the concentrations of residual ammonia and nitrogen oxides. NO2- and NO3- concentrations were approximately 1 mg/L at room temperature when the absorbed dose was 28.8 kGy. However, the apparent concentration of H2 significantly decreased with the N2 pressure and gas-liquid volume ratio. The loss fraction of ammonia considerably declined from 26.5% to 8.4% when the temperature increased from 25 to 200 ℃, demonstrating that the radiolysis of ammonia was suppressed at the elevated temperature. However, the concentrations of NO2- and NO3- increased to 34 and 3 times, respectively, at 200 ℃ compared to those at 25 ℃. In addition, a radiolysis model of ammonia-containing coolant was established in the present study. The maximum relative error between experimental data and calculation results at any temperature was 4.1%. The model was thereafter used to calculate residual ammonia concentration with the absorbed dose under different initial ammonia concentrations. The results revealed that it was necessary to replenish ammonia regularly when using it alone to inhibit oxidizing species.