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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.

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.

The direct copolymerization of ethylene with polar monomers to produce functional polyolefins continues to be highly appealing due to its simple operation process and controllable product microstructure. Low-cost nickel catalysts have been extensively utilized in academia for the synthesis of polar polyethylenes. However, the development of high-temperature copolymerization catalysts suitable for industrial production conditions remains a significant challenge. Classified by the resultant copolymers, this review provides a comprehensive summary of the research progress in nickel complex catalyzed ethylene-polar monomer copolymerization at elevated temperatures in the past five years. The polymerization results of ethylene–methyl acrylate copolymers, ethylene-tert–butyl acrylate copolymers, ethylene–other fundamental polar monomer copolymers, and ethylene–special polar monomer copolymers are thoroughly summarized. The involved nickel catalysts include the phosphine-phenolate type, bisphosphine-monoxide type, phosphine-carbonyl type, phosphine-benzenamine type, and the phosphine-enolate type. The effective modulation of catalytic activity, molecular weight, molecular weight distribution, melting point, and polar monomer incorporation ratio by these catalysts is concluded and discussed. It reveals that the optimization of the catalyst system is mainly achieved through the methods of catalyst structure rational design, extra additive introduction, and single-site catalyst heterogenization. As a result, some outstanding catalysts are capable of producing polar polyethylenes that closely resemble commercial products. To achieve industrialization, it is essential to further emphasize the fundamental science of high-temperature copolymerization systems and the application performance of resultant polar polyethylenes. [ABSTRACT FROM AUTHOR]

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.

Background In KEYNOTE-355 (NCT02819518), the addition of pembrolizumab to chemotherapy led to statistically significant improvements in progression-free survival and overall survival in patients with advanced triple-negative breast cancer with tumor programmed cell death ligand 1 (PD-L1) combined positive score of at least 10. We report patient-reported outcomes from KEYNOTE-355. Methods Patients were randomly assigned 2:1 to pembrolizumab 200 mg or placebo every 3 weeks for up to 35 cycles plus investigator's choice chemotherapy (nab-paclitaxel, paclitaxel, or gemcitabine plus carboplatin). The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire–Core 30 (QLQ-C30), Breast Cancer–Specific Quality of Life Questionnaire, and EuroQol 5-Dimension questionnaire visual analog scale were prespecified. Patient-reported outcomes were analyzed for patients who received at least 1 dose of study treatment and completed at least 1 patient-reported outcome assessment. Changes in patient-reported outcome scores from baseline were assessed at week 15 (latest time point at which completion and compliance rates were at least 60% and at least 80%, respectively). Time to deterioration in patient-reported outcomes was defined as time to first onset of at least a 10-point worsening in score from baseline. Results Patient-reported outcome analyses included 317 patients with tumor PD-L1 combined positive score of at least 10 (pembrolizumab plus chemotherapy: n = 217; placebo plus chemotherapy: n = 100). There were no between-group differences in change from baseline to week 15 in QLQ-C30 global health status/quality of life (QOL; least-squares mean difference = −1.81, 95% confidence interval [CI] = −6.92 to 3.30), emotional functioning (least-squares mean difference = −1.43, 95% CI = −7.03 to 4.16), physical functioning (least-squares mean difference = −1.05, 95% CI = −6.59 to 4.50), or EuroQol 5-Dimension questionnaire visual analog scale (least-squares mean difference = 0.18, 95% CI = −5.04 to 5.39) and no between-group difference in time to deterioration in QLQ-C30 global health status/QOL, emotional functioning, or physical functioning. Conclusions Together with the efficacy and safety findings, patient-reported outcome results from KEYNOTE-355 support pembrolizumab plus chemotherapy as a standard of care for patients with advanced triple-negative breast cancer with tumor PD-L1 expression (combined positive score ≥10). [ABSTRACT FROM AUTHOR]

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]

In our recent work, it was first demonstrated that aluminum (Al) ions generated in the process of H2O2 plasma sterilization can penetrate the sterilization package and contaminate the surgical instrument inside. In this paper, it is first reported that Al ions can be adsorbed in plasma by sterilization package with surface modification, significantly reducing the contamination, up to 92%. The surface modification is carried out by introducing a functional layer on the surface of the sterilization package. The special chemical groups in the functional layer can combine with Al ions in two ways, ion exchange and chelation, preventing them from contaminating the surgical instrument in the sterilization package. Through the research on the diffusion coefficient of Al in Si sterilized using the modified sterilization packages, it is found that surface modification of sterilization packages has a great influence on the physical mechanism of Al contamination. [ABSTRACT FROM AUTHOR]

In this paper, it is first demonstrated that Aluminum (Al) contamination is present; H2O2 plasma sterilization is widely used for sterilization of surgical instruments. The contamination amount of Al can reach as high as 7.9 × 1012 atoms/cm2. Aluminum is well known as a harmful element to human health, which may damage bones and the brain. During the use of the surgical instruments after H2O2 plasma sterilization in surgery, the contaminated Al may enter and reside in the human body and threaten the health and even life safety. Therefore, it is necessary to study the Al contamination present in H2O2 plasma sterilization to arouse public attention and take countermeasures. The physical mechanism of the Al contamination presented in H2O2 plasma sterilization is diffusion. In our previous study, we developed two physical models for calculating the diffusion coefficient. In this study, both models are used to calculate the diffusion coefficient of the contaminated Al in sterilized Si samples. From the calculation results, it is inferred that the contamination mechanism of Al presented in H2O2 plasma sterilization is closer to the model, where the diffusion coefficient value is a function of the plasma treatment time. [ABSTRACT FROM AUTHOR]