Zhi Cao

Hydroxylamine nitrate (HAN) and hydrazine nitrate (HN) are commonly found in radioactive waste solutions in nuclear fuel reprocessing, and their efficient removal is essential for waste treatment processes. In this study, six activated carbon carriers were selected to prepare Ru/AC catalysts for the simultaneous catalytic decomposition of HAN and HN, with the aim of exploring the effect of carrier properties on catalytic performance. The catalyst’s activity was evaluated in a batch reaction unit, and its structural properties were characterized using N₂ physical adsorption, XRD, SEM, and TEM techniques. The results revealed that the catalyst’s activity was primarily determined by the carrier’s particle size and specific surface area. Additionally, corrosion-induced damage to the pore structure and Ru loss were identified as the main factors responsible for catalyst deactivation. This study highlights the importance of optimizing carrier structure to enhance the activity and stability of Ru/AC catalysts.

Fast-neutron reactors are an important representative of Generation IV nuclear reactors, and due to the unique structure and material properties of fast reactor fuel, traditional mechanical cutting methods are not applicable. In contrast, laser cutting has emerged as an ideal alternative. However, ensuring the stability of optical fibers and laser cutting heads under high radiation doses, as well as maintaining cutting quality after irradiation, remains a significant technical challenge. Here, we study the performance changes in optical fibers exposed to a total radiation dose of 10⁵ Gy, focusing on power transmission and thermal characteristics. By integrating irradiated optical fibers with irradiated laser cutting heads, simulated cutting experiments on the hexagonal tubes of spent fuel from fast reactors (fast reactor simulation assembly) were conducted. Critical cutting quality parameters, including kerf width, surface roughness, and slagging length, were analyzed. The results indicate that, while the power transmission performance of irradiated optical fibers shows slight degradation, its impact on cutting quality is minimal. High-quality cutting can still be achieved under optimized parameters. This study confirms the feasibility of laser cutting technology in high-radiation environments and provides essential technical support for its application in nuclear fuel reprocessing.

Employing catalytic decomposition to break down reducing agents in intermediate-level radioactive waste during nuclear fuel reprocessing offers significant advantages. This study focuses on investigating the deactivation behavior of 5% Ru/C catalysts by two different synthesis processes used for reducing agent destruction. Deactivation experiments were conducted by subjecting the 5% Ru/C catalysts to 100 and 150 reaction cycles. Changes in the concentration of free radicals on the carbon-based carrier were measured to analyze the loading position and loss of Ru ions. Additionally, sorption–desorption curves and pore size distributions of the four catalysts were obtained. Analysis results reveal that Ru ions on the catalyst adsorb onto active free radical sites on the carbon-based carrier. Under ultrasonic conditions, some Ru ions partially desorb from the free radical sites on the carbon-based carrier, and desorbed Ru ions may adsorb onto weak free radical sites, while undesorbed Ru ions may adsorb onto strong free radical sites. After hundreds of hours of reaction, SM1 and SM2 exhibited approximately a 30% decrease in specific surface area and pore volume compared to SM0. However, the catalyst activity remained unchanged, and the catalyst pore size remained essentially unchanged, which primarily means that the micropores on the catalyst’s surface have undergone corrosion and damage.

In recent years, optical fibers have found extensive use in special environments, including high-energy radiation scenarios like nuclear explosion diagnostics and reactor monitoring. However, radiation exposure, such as X-rays, gamma rays, and neutrons, can compromise fiber safety and reliability. Consequently, researchers worldwide are focusing on radiation-resistant fiber optic technology. This paper examines optical fiber radiation damage mechanisms, encompassing ionization damage, displacement damage, and defect centers. It also surveys the current research on radiation-resistant fiber optic design, including doping and manufacturing process improvements. Ultimately, it summarizes the effectiveness of various approaches and forecasts the future of radiation-resistant optical fibers.

The thermal stability of N, N-dimethylhydroxylamine (DMHAN) in the HNO3 solution was studied using microcalorimeter. The influence of concentration of HNO3, DMHAN, methylhydrazine (MH), atmosphere (air and nitrogen), and metals was investigated. The kinetic parameters and self-accelerating decomposition temperature (SADT) of the feed in process (stripping reagents 1BX, scouring agent 2DS, stripping reagents 2BX, and waste aqueous phase 2DW) were calculated by Advanced Kinetics and Technology Solutions (akts) thermokinetics software. The molar enthalpy of the reaction of NaNO2 with DMHAN and MH was also determined. The results show that the initial reaction temperature (T0) of DMHAN/HNO3 (HNO3: 1.5–3.0 mol/L, DMHAN: 0.05–0.8 mol/L) is increased as the acidity is reduced or the concentration of DMHAN is increased. Holding reductant MH made the induction period of the autocatalytic reaction longer. The air, nitrogen atmosphere, Fe, and the fission products (Zr, Ru) do not affect the decomposition of DMHAN, but the stainless steel made the T0 of DMHAN/HNO3 become lower. The SADT of 1BX/2DS, 2BX, and 2DW is 56 °C, 52 °C and 47 °C, respectively. The molar enthalpies of formation of the reaction of NaNO2 with DMHAN and MH are −411.3 kJ/mol, −246.0 kJ/mol, respectively.