Study on damage evolution and radon exhalation of uranium-bearing granite under high temperature.

Deep geological disposal of high-level radioactive waste is a feasible method for solving the problem of spent fuel storage in China. High-level radioactive waste releases heat during the decay process, which increases the temperature of the surrounding rock in the repository, resulting in a significant increase in radon concentration. In this study, the surrounding rock (granite) of a high-level radioactive waste repository was taken as the research object and, based on the similarity principle, an orthogonal test designed. Similar materials of uranium-containing granite were prepared in the laboratory and the physical and mechanical properties and cumulative radon concentration of granite samples assessed under different temperatures (25, 50, 100, 150, and 200 °C). The results showed that, with increased temperature, the compressive and tensile strengths of samples gradually increased and their pore volume gradually decreased. After heat treatment, the longitudinal wave velocity and thermal conductivity of samples decreased linearly with increased temperature. The radon exhalation rate first increased and then decreased, with the rate reaching a maximum at 100 °C. The radon exhalation rate of single-sided and double-sided samples was 0.00914 and 0.00460 Bq·m-2·s-1, respectively. When the temperature was 25-100 °C, the dominant stage was pore water. The radon exhalation rates of samples were positively correlated with compressive and tensile strengths and negatively correlated with pore volume, longitudinal wave velocity, and thermal conductivity. The temperature of 100-200 °C was range of the dominant stage of pore structure. The conclusions obtained in this study can provide theoretical support for radon reduction and radon control of granite in high temperature environments.

Preparation and related properties of geopolymer solidified uranium tailings bodies with various fibers and fiber content.

Uranium tailing ponds are a potential major source of radioactive pollution. Solidification treatment can control the diffusion and migration of radioactive elements in uranium tailings to safeguard the surrounding ecological environment. A literature review and field investigation were conducted in this study prior to fabricating 11 solidified uranium tailing samples with different proportions of PVA fiber, basalt fiber, metakaolin, and fly ash, and the weight percentage of uranium tailings in the solidified body is 61.11%. The pore structure, volume resistivity, compressive strength, radon exhalation rate variations, and U(VI) leaching performance of the samples were analyzed. The pore size of the solidified samples is mainly between 1 and 50 nm, the pore volume is between 2.461 and 5.852 × 10-2 cm3/g, the volume resistivity is between 1020.00 and 1937.33 Ω·m, and the compressive strength is between 20.61 and 36.91 MPa. The radon exhalation rate is between 0.0397 and 0.0853 Bq·m-2·s-1. The cumulative leaching fraction of U(VI) is between 2.095 and 2.869 × 10-2 cm, and the uranium immobilization rate is between 83.46 and 85.97%. Based on a comprehensive analysis of the physical and mechanical properties, radon exhalation rates, and U(VI) leaching performance of the solidified samples, the basalt fiber is found to outperform PVA fiber overall. The solidification effect is optimal when 0.6% basalt fiber is added.

Biocompatible semiconducting polymer nanoparticles as robust photoacoustic and photothermal agents revealing the effects of chemical structure on high photothermal conversion efficiency.

Understanding the relationship between polymer chemical structure and its performance of photoacoustic imaging (PAI) and photothermal therapy (PTT) is important for developing ideal PAI/PTT agents. In this report, four semiconducting polymer nanoparticles (SPNs) with different donor-acceptor architectures are self-assembled for highly effective PAI-guided PTT. In particular, SPN1 with the longest π-conjugation length and the highest mass extinction coefficient which are beneficial for intramolecular charge transfer as well as light harvesting, exhibits the highest photothermal conversion efficiency up to 52.6%. Moreover, the as-prepared SPN1 possess good water-dispersibility, robust size-stability and excellent photothermal properties. Furthermore, the SPN1 not only exhibits a remarkable cancer cell-killing ability but also shows a prominent tumor inhibition capacity. Finally, the as-prepared water-dispersible SPN1 displays good biocompatibility and biosafety, making it a promising candidate for future biomedical applications. Considering the plenty of near-infrared absorbing semiconducting polymer available, our work provides fundamental insights for rational design and preparation of highly efficient SPN-based PAI/PTT agents for cancer theranostics.