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BackgroundSubchannel analysis of fuel assemblies is critical for the development of lead-bismuth reactors.PurposeThis study aims to modify and optimize the COBRA subchannel program to make it suitable for lead-bismuth reactors and validate its performance.MethodsModifications were made to the COBRA subchannel program, involving adjusting physical properties, convective heat transfer models, friction models, and turbulence mixing models. The performance of the modified program was evaluated by comparing its numerical calculation results to experimental data. To optimize results over a wide range of mass flow rate conditions, an optimization method based on a subchannel model and coupled with a neural network was proposed, and the influence of mass flow rate on calculation accuracy was analyzed.ResultsThe comparison results demonstrate that the modified subchannel program performs well under experimental conditions, with an error of no more than 5% compared with experimental results and no more than 3% compared with FLUENT results. The application of neural networks is found to improve accuracy and reduce errors by an order of magnitude.ConclusionsThe optimized subchannel analysis method, derived from the modifications and neural network coupling, can accurately predict outlet temperatures for lead-bismuth reactors under a wide range of mass flow rate conditions. This method provides valuable guidance for the design of such reactors.

Under high-temperature conditions, supercritical carbon dioxide (S-CO2) power conversion systems have significant advantages, which show great potential in improving energy utilization efficiency, reducing environmental pollution, and realizing sustainable energy development. S-CO2, as a high-efficiency working fluid, can achieve high efficiency in higher temperature thermodynamic cycles, which helps to reduce fuel consumption and greenhouse gas emissions. Since the S-CO2 power cycle is significant to energy conversion and utilization, many researchers have conducted experimental studies on the convective heat transfer characteristics of S-CO2. However, existing studies mainly focus on low-temperature condition (10-200 ℃), and experimental data under hightemperature condition (200-500 ℃) are scarce. Most of the research conditions on the heat transfer characteristics of S-CO2 have not reached the optimal temperature range of the S-CO2 power conversion system, in order to master the critical data of the relevant design, it is necessary to carry out experimental research on the heat transfer characteristics of S-CO2 under high heat flux conditions, which holds a crucial significance in the development of associated power conversion systems. This paper first introduced the construction process of the S-CO2 forced circulation test bench, and evaluated the uncertainty of the relevant experimental data. The main temperature range of the experiment is 450-800 K, the pressure range is 7.40-10.22 MPa, and the heat flux range is 20-1 000 kW/m2. The heat transfer characteristics of S-CO2 in a vertical tube under high-temperature conditions were studied experimentally, and the effects of thermal acceleration and buoyancy on heat transfer were analyzed. The results show that the heat transfer trend of S-CO2 is similar to that of gaseous CO2 under high-temperature conditions, but the values are quite different, and the influence of thermal acceleration and buoyancy effect on the heat transfer of high-temperature S-CO2 is negligible. Finally, in order to develop a reliable prediction method of S-CO2 convection heat transfer under high-temperature conditions, this paper collected the empirical correlations of S-CO2 heat transfer in vertical heating circular tubes commonly found in the literature, and analyzed them under high heat flux, evaluated and analyzed their experimental prediction high-temperature conditions. It is found that there are some differences with the existing experimental data. Therefore, this paper proposes an empirical correlation suitable for high-temperature S-CO2 heat transfer. The newly proposed heat transfer correlation has the highest calculation accuracy, which calculates 96.65% of experimental data within ±10% error. It can achieve higher accuracy, which meets the actual engineering needs.

Compared with traditional large scale pressurized water reactor, the volume of the containment of small pressurized water reactor is small. During a loss of coolant accident (LOCA), the containment pressure of small pressurized water reactor rises rapidly and measures such as pressure suppression pool should be taken to maintain the containment integrity. The pressure suppression pool can be used to quickly relieve the containment pressure, and the containment spray can be used to continuously relieve the containment pressure. However, the existing research on pressure suppression pool is mainly aimed at large scale reactor and mainly focuses on the thermal-hydraulic phenomenon in the containment, and the design scheme of using both containment spray and pressure suppression pool is rarely discussed. In order to investigate the suppressant characteristics of the pressure suppression pool in the suppression containment, the small pressurized water reactor pressure suppression pool and containment spray system simulation facility were modeled, the containment pressure suppression process with the best estimate system computer code RELAP5 was simulated. Condensation and flash evaporation of water could make it difficult to accurately calculate the containment pressure, RELAP5’s capability to simulate pressure changing under different conditions was assessed. The influence of the trend of break discharge on the simulation and design of the pressure suppression pool was analyzed. The suppressant effect of flow area of pressure suppression pipeline and gas-water ratio in pressure suppression pool was compared under different break flow rates and containment spray mass flow rates. The results show that the flow area of pressure suppression pipeline and gas-water ratio in pressure suppression pool have optimal value, and the optimal value of the flow area of pressure suppression pipeline is generally small. The break flow rate is affected by the area of the break. Under the same conditions of total mass and energy release, the faster the break flow rate, the greater the optimal values for the flow area of pressure suppression pipeline and gas-water ratio in pressure suppression pool. The pressure suppression effect will be weakened more obviously if the flow area of pressure suppression pipeline is lower than the optimal value. The continuous pressure suppression ability will be lost if the gas-water ratio is higher than the optimal value. As the containment spray mass flow rate increases, the optimal value for the flow area of pressure suppression pipeline remains unchanged, but the optimal value for the gas-water ratio increases. The research results can provide reference for the design and analysis of the small suppression containment.

Purpose. This study was performed to measure the concentration of trans-resveratrol and its three metabolites in human eyes. Methods. The patients who underwent pars plana vitrectomy for rhegmatogenous retinal detachment were included. The participants were orally given trans-resveratrol-based supplement (Longevinex®). A suitable amount of conjunctiva, aqueous humor, and vitreous humor were obtained during the operation. High-performance liquid chromatography (HPLC) with mass spectrometry (LC/MS/MS) was used to detect the concentration of trans-resveratrol and its three metabolites in the various samples. Results. The average concentration of resveratrol in the conjunctiva was 17.19 ± 15.32 nmol/g (mean ± SD). The concentration of resveratrol in the aqueous humor was close to the limit of detection, but its metabolites could be quantified. The concentrations of resveratrol metabolites in the aqueous humor can be detected. In the vitreous humor, the average concentration of resveratrol-3-O-sulfate was 62.95 ± 41.97 nmol/L. The sulfate conjugations of resveratrol were recovered in the conjunctiva, aqueous humor, and vitreous humor. Conclusions. Resveratrol and its three metabolites can be detected in the ocular tissues after oral administration. Although the concentration of parent resveratrol was low in the eyes, its metabolites could be detected and may have a role in the treatment of ocular diseases.

As a cutting-edge wood preservation technology, injection treatment to living trees has gained traction to prevent fungal infestation. Wood preservatives are injected into the lower part of the trunk and subsequently transported with xylem sap through transpiration. In this experiment, the waterborne wood preservative was synthesized by Ammoniacal Copper Quaternary (ACQ) and carbon dots (CDs), and its characteristics were determined. The distribution, loading capacity, and decay resistance of ACQ/CDs at different heights of the living poplar trees after the treatment were examined. Meanwhile, the effects of three methods, i.e. injection treatment, immersion treatment, and pressure treatment on the decay resistance and mechanical properties of the treated wood were explored. The results showed that the wood preservative penetrated well into the xylem after the injection treatment. The wood at different heights after the injection treatment had good decay resistance. The decay resistance diminished with the rise in tree height, attributable to variations in the timing of the preservative reaching different levels within the tree. When compared with the immersion and pressure treatments, the injection treatment can effectively reduce the influence of long-term preservative soaking and pressure application on the mechanical properties of the treated wood, while upholding commendable decay resistance. [ABSTRACT FROM AUTHOR]