Search

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.

Epoxy resin (EP) has good mechanical and insulating properties and is widely used in the aerospace and nuclear industry. However, it can become degraded and failure-prone in high-energy radiation environments. Although boron nitride (BN) is stable in high-radiation fields, the actual performance of the radiation stability of BN is limited owing to its poor compatibility with the polymer matrix. In this study, boron nitride nanosheets (BNNSs) were modified by applying radiation to prepare BNNSs modified by glycidyl-methacrylate (BNNSs@PGMA), which has good compatibility with EP. Then, BNNSs@PGMA were introduced into the EP matrix by employing solution blending to prepare EP composites: EP, BNNSs/EP, and BNNSs@PGMA/EP. Moreover, the changes in the properties of these composites before and after γ-ray irradiation were investigated. The results indicated that the tensile strength of EP composites first increased and then decreased with an increasing absorbed dose. Radiation crosslinking dominated in the case of an absorbed dose of 0-400 kGy, whereas radiation cracking played a leading role for an absorbed dose of 400-1 000 kGy. For the absorbed dose of 1 000 kGy, the tensile strength of EP decreased by 42.9%, whereas that of BNNSs@PGMA/EP decreased by only 21.3%, which indicated more excellent radiation resistance. In addition, the resistance of the composites was improved by increasing the degree of modification in BNNSs@PGMA.

As the decay daughter of 99Mo, 99mTc is the most widely used radioisotope in the field of nuclear medicine. Recently, the major 99Mo production reactors in the world are facing problems such as unplanned maintenance, shutdown and decommission, resulting in the unstable supply of 99Mo. Therefore, many developed countries have been actively exploiting alternative technologies for 99Mo production. In this paper, various 99Mo-production technologies by particle accelerator instead of reactor were introduced, and the research progress of producing 99Mo based on electron accelerator was summarized at home and abroad. The accelerator performance index and the key technologies in the production process were discussed in detail, such as the design of irradiation device and target, separation of 99mTc, recovery of 100Mo and waste management. In addition, some suggestions were put forward for the basic and applied research of relevant technologies in China and the commercialization of 99Mo production by electron accelerator.

In this study, poly 4-vinylpyridine-modified multilayered mesoporous silica (FS-VP) was synthesized by radiation grafting, and the effects of the synthesis conditions on the grafting ratio were investigated. The results of Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) indicated that the grafting ratio of FS-VP reached the maximum value of 27.8% under the following conditions: 4-vinylpyridine (4-VP) monomer concentration, 50%; radiation dose rate, 3 kGy/h; and absorbed dose, 72 kGy. In addition, quaternized FS-VP (FS-VPQ) was prepared, and its adsorption performance for Re(VII) was also studied. The adsorption capacities were the maximum at pH 2 and 3. The adsorption isotherm of FS-VPQ for Re(VII) conformed to the Langmuir model. The saturated adsorption capacity reached 68.0 mg/g at pH 3. The high adsorption capacity was attributed to the high specific surface area of the multilayered pore structure and the two inherent positive charges of the adsorbent after quaternization. Moreover, due to the high mass transfer rate resulting from the multilayered pore structure, FS-VPQ reached adsorption equilibrium within 3 min. The findings of this study provide theoretical guidance for Re separation and enrichment technology, and also can serve as reference for the separation of Tc from radioactive waste liquids.

Copper and copper alloys are widely used in the field of nuclear materials. The effects of aqueous solutions that have undergone copper ion radiolysis on the generation of H2O2, O2, and H2 must be considered for material corrosion control and hydrogen explosion risk assessment. In this study, a γ-radiolysis experiment of an aqueous solution containing copper ions was conducted to explore the effects of different absorbed doses, absorption dose rates, and Cu2+ concentrations on the generation of H2O2, O2, and H2. The results showed that with an increase in the absorbed dose (0-1.80 kGy), the concentrations of H2O2 and H2(g) firstly increased and then tended to stabilize under steady-state concentrations of 5.41×10-6 and 7.91×10-5 mol/L, respectively, whereas the concentration of O2(g) remained at 9.04×10-4 mol/L. The presence of Cu2+ enhanced the equilibrium concentrations of H2 and H2O2 by one and two orders of magnitude, respectively, which in turn promoted the generation of H2O2 and H2; however, it had a negligible effect on O2 generation. The equilibrium concentrations of H2O2 and H2 increased with an increase in the absorption dose rate. Specifically, when the absorption dose rate was increased from 1.40 to 46.93 Gy/min, the equilibrium concentrations of H2O2 and H2 increased from 4.56×10-6 and 1.78×10-5 mol/L to 2.46×10-5 and 3.81×10-4 mol/L, respectively, whereas O2 remained essentially unaffected within this absorption dose rate range. In addition, based on the kinetics of water radiolysis and two-film theory of gas-liquid mass transfer, we constructed a calculation model for the radiolysis of aqueous solutions containing copper ions. Compared with the experimental data, the absolute values of the normalized mean bias in the simulation results were mostly between 1% and 7%, with a maximum of approximately 24%, thereby demonstrating the effectiveness and correctness of the calculation model. Accordingly, the model was used to calculate the radiolytic behavior of an aqueous solution containing copper ions under C6+ ion irradiation, and the simulation results matched well with the experimental data reported in the literature, indicating that the model can be expanded to other applications.

In this study, the γ-radiolysis of boric acid-lithium hydroxide-ammonia coolant was investigated under different conditions, including boric acid concentration, absorbed dose, and absorbed dose rate. The concentrations of H2O2, NO2-, and NO3- were determined using UV-visible spectroscopy and ion chromatography. With an increase in boric acid concentration, the concentrations of H2O2 and NO2- in the coolant system did not change significantly within a pH range commonly used in pressurized water reactor operation. Specifically, the concentration of H2O2 varied from 9.28×10-5 to 1.07×10-4 mol/L, while that of NO2- changed from 0.9×10-5 to 1.5×10-5 mol/L. In contrast, the concentration of NO3- fluctuated significantly, ranging from 4×10-5 to 8×10-5 mol/L. With an increase in the absorbed dose (1-30 kGy), the equilibrium concentration of H2O2 and NO2- in boric acid-lithium hydroxide-ammonia system increased to 1.28×10-4 mol/L and 1.30×10-5 mol/L, respectively. Meanwhile, the concentration of NO3- did not change significantly (4×10-5 to 6×10-5 mol/L). The concentrations of the three radiolytic products were not significantly affected within the given absorbed dose rate range (1.27 to 18.86 Gy/min). Overall, this work provides valuable basic data for optimizing the new boric acid-lithium hydroxide-ammonia coolant system.

In this work, the effects of the tungsten (W) converter and molybdenum target thickness on the 99Mo yield in the production of 99Mo via 100Mo(γ, n)99Mo photonuclear reaction were studied. The FLUKA program was applied to simulate the optimal size of the targets for the production of 99Mo under 50 MeV electron conditions, where the thicknesses of the W and Mo targets were 0.3 and 1.4 cm, respectively. The relative error between the calculation and the experimental results was less than 8%. The process of irradiating natural (natMo) and enriched (100Mo) molybdenum targets using electrons with a 1 mA average beam current was further simulated. The specific activity of enriched 100Mo is nearly ten times higher than that of natMo. The use of 100Mo targets also produces fewer radioactive impurities. This study provides a guidance on the size of W conversion and molybdenum targets, as well as the selection of molybdenum species, when producing 99Mo via photonuclear reaction. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) composite aerogels were synthesized by the radiation reduction of graphene oxide (GO) with the assistance of Eu3+, which demonstrated excellent adsorption performance for diverse organic pollutants. Eu3+ promoted the formation of the gel by inducing the pre-assembly of GO so that the required pH range for synthesizing the rGO aerogel by radiation reduction was broadened and the minimum absorbed dose was also reduced. At pH 2, the Eu3+-induced pre-assembly fabricated more mesopores and enlarged the specific surface area of the obtained hierarchically porous rGO-Eu composite aerogel, which enabled the high-capacity (81–395 g g−1) and ultrafast removal of organic solvents. The different effects of organic solvents on the unique fluorescence emission of Eu(III) also allowed the in situ detection of certain organic solvents such as pyridine. At pH 6, Eu3+ enhanced the reduction of GO by capturing more hydrated electrons, the most reductive species produced by water radiolysis, and synergistically reduced GO. The obtained rGO-Eu composite aerogel with a high reduction degree, demonstrated outstanding adsorption capacities for various anionic organic dyes (40.5–1572.5 mg g−1) owing to the strong π–π interaction and electrostatic attraction. Benefitting from high reduction, it demonstrated adsorption capacity for cationic dyes (97.3–1367.6 mg g−1) comparable to other reported graphene-based aerogels. The rGO-Eu aerogel prepared by radiation reduction might be suitable as a broad-spectrum adsorbent for organic pollutants. [ABSTRACT FROM AUTHOR]