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BackgroundThe separation and removal of fission products and the recovery of carrier molten salt during nuclear fuel reprocessing in molten salt reactors reduces waste and facilitates useful substance recycling.PurposeThis study aims to separate and remove the rare earth (RE) fission products and recovery of carrier molten salts.MethodsFirstly, high temperature precipitation reactions of rare earth (RE = Ce, Nd, Sm, Eu, Y, Yb) and thorium fluorides were studied in LiF-BeF2 melt using sodium sulfide hydate (Na2S·5H2O) as the precipitant. Their removal ratios were subsequently compared under different conditions. Then, a combined precipitation distillation method was employed to further heat the precipitated mixed salt to 950 °C and distilled under vacuum conditions at a pressure of 10 Pa for 20 min. The content and removal ratio of rare earth Nd, as well as contents of oxygen and sulfur, in condensed collected salts were investigated after using above improved precipitation-distillation processing. Finally, further analysis of the composition of sediment was conducted using X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectrometer (EDS).ResultsThe results demonstrate that RE removal ratios are less than 90% when the RE to precipitant ratio is 1:2 at 600 ℃ whilst the RE Nd content in the salt collected by condensation is reduced to 1.39×10-4 g∙g-1, and its removal ratio is increased to 99.6% with further improved precipitation-distillation processing. Simultaneously, the oxygen and sulfur contents are 8.5×10-5 g∙g-1 and 1.50×10-4 g∙g-1, respectively. Analysis results of XRD, XPS and EDS indicate that the sediment mainly consists of RE sulfide and sulfur oxide.ConclusionsThis study confirms the feasibility of separating RE from waste salt using the sulfide precipitation method and that over 99% RE separation efficiency can be achieved using precipitation-distillation combined treatment. Therefore, this provides a reference method for purifying waste salt and realizing molten salt reuse.

BackgroundIn thorium-based molten salt reactors (TMSRs), 233Pa is an important intermediate nuclide in the conversion chain of 232Th to 233U, and 233PaF5 can be effectively separated from carrier salt by low-pressure distillation. However, some of the metal fluoride is vaporized along with 233PaF5 simultaneously, and the evaporated fluoride may condense at different temperatures.PurposeThis study aims to investigate the condensation behavior of 233PaF5 and other key metal fluorides in the FLiBeZr molten salt during the low-pressure distillation process.MethodThe FLiBeZr molten salt containing PaF5 and various metal fluorides was low-pressure distillated to examine the condensation behavior of 233PaF5 and key metal fluorides at different temperatures. Then, the optimal temperature of key metal fluorides was evaluated and the separation characteristics between them and 233PaF5 were figured out. Finally, the separation factors of 233PaF5 and the other metal fluorides were calculated and compared with those of the entire low-pressure distillation process at the optimum condensation temperature of 233PaF5.ResultsThe results show that the optimal condensation temperature for 233PaF5 and 95NbF5 is within the range of 600~700 ℃, whilst it is within the range of 400~500 ℃ for 237UF4 and 95ZrF4. The comparison results show that there is no significant difference in the separation factors of 95NbF5 and 233PaF5, but the separation factors of 233UF4 and 95ZrF4 are increased by a factor of two to 20 times.ConclusionIt is confirmed that the separation coefficient is determined primarily by volatilization, but can be further improved by varying the condensation temperature.

In this paper, we first preprocess the English-translated text to extract the statistical features of Chinese culture in the translated text using the TF-IDF model as well as the semantic features of Chinese culture using the Word2Vec model. Then, the Chinese cultural contents in English audio, text and video are extracted respectively, and the best way to integrate Chinese culture into English translation is analyzed through feature fusion. Based on the concept of multimodal teaching, a multifaceted teaching model of English translation incorporating Chinese culture was constructed, and the effect of the teaching model was evaluated through the dimensions of students’ performance, Chinese culture awareness, and teaching feedback. The results show that after multimodal teaching sig.=0.03

In view of the requirements of USV independently-performed antisubmarine mission based on the dipping sonar, this essay analyses the characteristics of the use of dipping sonar, constructs the detection probabilistic model of the dipping sonar, designs the control process of autonomous USV antisubmarine by using the dipping sonar, realizes the task planning model of submersible search based on probabilistic model and the quality of submersible search. Through the simulation calculation, this essay points out that the input parameters of the algorithm are less, and the output planning can meet the control requirements of USV antisubmarine mission with good performance and expected goals.

BackgroundAn electrolyte waste salt containing LiCl and various products is generated during the pyroprocessing of spent nuclear fuel in metal fast reactors. Separating metal impurities from waste salt can purify molten salt, facilitate salt recycling, and reduce the amount of waste salt, achieving waste minimization.PurposeThis study aims to investigate the effects of key factors on the application of the cold finger crystallization method used for removal of Sr and Ba from molten LiCl salt.MethodsA homemade cold finger experimental apparatus was applied to the experimental removal of two alkaline earth metals, Sr and Ba, from molten LiCl salt, and Fluent software was employed to simulate the application of cold finger crystallization equipment during dry reprocessing. The effects of crystal growth time, initial crystallization temperature, and initial SrCl2/BaCl2 concentrations on the removal ratio of the crystalline salt during the process were analyzed.ResultsThe initial temperature of molten salt is a critical factor that influences cold finger separation efficiency. When the initial temperature reaches 660 ℃, the removal efficiency improves. Moreover, when the impurity contents of Sr and Ba in molten salt are lower than 0.55%(w/w), the removal efficiency of the cold finger crystallization method can exceed 80%. Further analysis shows that the removal effects of different parts of molten salt crystals differ. The solvent salt at the top of the molten salt crystal is better, and the removal ratio of the bottom and inner salts is lower. Therefore, the optimal conditions for removing Sr and Ba from LiCl crystalline salt require an initial temperatures of 660~670 ℃, an airflow intensity of 10 L·min-1, and a growth time of 20 min. Under these optimal conditions, the removal ratio can reach 90%.ConclusionsThe proposed approach is feasible for purifying solvent salts from electrolyte waste molten salt via cold finger crystallization. This study provides a reference for purifying waste salt and reusing molten salt.

BackgroundIn molten salt reactor, the concentration of oxygen impurities in the molten salt should be strictly controlled to avoid the potential safety risks caused by the reaction of O2- in the carrier salt with UF4 fuel to generated UO2 precipitation.PurposeThis study aims to investigate the evaporation behavior of the main oxygen-containing impuritiy ions in carrier salt at high temperature and low pressure and the influence of process parameters such as temperature, pressure and initial oxygen content of molten salt on the removal of O2- in carrier salt.MethodsThe vacuum distillation method was employed and a vacuum distillation device were used to carried out experimental study of the separation behavior of the main oxygen-containing impurities NO3-, SO42-, PO43- and O2- in the carrier salt during vacuum distillation. The removal mechanism of the above ions was explored, and the specific influence of process conditions on the separation effect of O2- distillation was investigated.ResultsThe results show that the removal ability of oxygen-containing impurities by vacuum distillation is NO3-＞PO43-＞SO42-＞O2-. The removal capacity of O2- increases with the increase of temperature, and the recovered salt with a total oxygen content about 2.40×10-4 g·g-1 salt is obtained at 1 050 ℃. The phenomenon of oxygen with a total oxygen content about 2.50×10-4 g·g-1 salt is observed when the pressure is higher than 40 Pa. The oxygen entrainment is increased during the evaporation of molten salt with the decrease of pressure, and the recovered salt content in the recovered salt continued to decrease with the decrease of the initial content of O2- in the carrier salt, which confirmed the technical feasibility of melting salt multiple distillation to remove oxygen.ConclusionsIt is verified by study shows that vacuum distillation can remove oxygen-containing impurities from carrier salt effectively and achieve the rapid and efficient purification of the carrier salt.

The bio‐based plasticizers‐glycerol and lactic acid were used to plasticize and compatibilize PVA/PLA blends during melt blending process. It was confirmed that lactic acid significantly improved the compatibility between glycerol‐plasticized PVA and PLA. Compared with pure PVA, the melting and crystallization temperatures and crystallinities decreased but the crystal form of PVA in the blends was not changed. The thermal stabilities of PVA/glycerol (G)/lactic acid (L)/PLA blends were better than PVA/G/PLA blends. Compared to PVA/G/PLA blends, the tensile and tear strength of PVA/G/L/PLA blends were improved, however, elongation at break decreased. The water absorptions and water vapor permeances of the blends decreased with the addition of hydrophobic PLA, but they increased by incorporation of hygroscopic lactic acid. The surface resistivities of the blends augmented in combination with PLA but declined by adding lactic acid. The melt flow rates of PVA/G/PLA blends were better than PVA/G/L/PLA blends because lactic acid enhanced the interactions among the components. After the addition of lactic acid, the transmittances of the blends increased due to the refined dispersed phases by the compatibilization. The compatibility between the components was predicated by Hansen solubility parameters. These blends showed potential as a novel barrier material for food and medicine packages. Highlights: PVA, glycerol, and PLA blends were compatibilized by lactic acid.The melting temperatures decreased with addition of glycerol and lactic acid.The tensile and tear strengths were enhanced with addition of PLA and lactic acid.The hydrophobicity, melt fluidity, and surface resistivity were improved by PLA. [ABSTRACT FROM AUTHOR]