Effect of reprocessing on neutrons of a molten chloride salt fast reactor

Due to their unique features,such as the inherent safety,simplified fuel cycle,and continuous on-line reprocessing,molten salt reactors(MSRs)are regarded as one of the six reference reactors in the Generation IV International Forum(GEN-IV).Molten chloride salt fast reactors(MCFRs)are a type of MSR.Compared to molten fluoride salt reactors(MFSRs),MCFRs have a higher solubility of heavy metal atoms,a harder neutron spectrum,lower accumulation of fission products(FPs),and better breeding and transmutation performance.Thus,MCFRs have been recognized as a type of MSR with great prospects for future development.However,as the most important feature for MSRs,the effect of different reprocessing modes on MCFRs must be researched in depth.As such,this study investigated the effect of different isotopes,especially FPs,on the neutronic performance of an MCFR,such as its breeding performance.Furthermore,the characteristics of the different reprocessing modes and MCFR rates were analyzed in terms of safety,radioactivity level,neutron economy,and breeding capacity.In the end,a reprocessing method suitable for MCFRs was determined through calculation and analysis,which provides a reference for the further research of MCFRs.

Preparation of Periclase-forsterite Lightweight Heat-insulating Refractories by Molten Salt Method

Low grade magnesite is one of the main research directions in the future as the raw material for the preparation of magnesia based insulating refractories.Periclase-forsterite(MgO-Mg_(2)SiO_(4)) lightweight insulating refractories were prepared by the molten salt method with high silica magnesite and tertiary talc ore as raw materials by pretreating them to get light burnt magnesia and talc,and NaCl molten salt as the reaction medium.The effects of the NaCl addition,the sintering temperature,the holding time and the raw material ratio on the sample preparation were studied.The results show that when the NaCl addition is 20% of the mass of light burnt magnesia and talc mixture,the sintering temperature is 1 200 ℃,the holding time is 6 h,and m(light burnt magnesia):m(talc)=5:5,the sample has the optimal comprehensive properties:the bulk density of 1.46 g·cm^(-3) and the apparent porosity of 55.0%.In addition,it is found that self-decomposition of talc and the formation of forsterite can form pores inside the sample.

Micromorphology and texture of niobium coating electrodeposited in NaCl−KCl−CsCl molten salt system

A low-toxicity and environment-friendly NaCl−KCl−CsCl−K_(2)NbF_(7) system was used to prepare Nb coatings on Mo substrates.The effects of temperature,current density and electrodeposition time on the micromorphologies and textures of the electrodeposited Nb coatings were studied.The results showed that Nb coatings obtained at 30−70 mA/cm^(2) in the temperature range of 700−750℃ were continuous and compact,with a hardness range of 2.16−2.45 GPa.As the columnar crystals grew with time,the preferential growth orientations of the Nb coatings changed from<200>to<211>and then became disordered.With increasing polarization,the morphologies of the Nb coatings changed from hexagonal star-like surface to conical or pyramid-like surface.

Deep Potential Molecular Dynamics Systematic Study of Microstructure and Thermophysical Properties of NaCl-CaCl_(2) Molten Salt System across Phase Transition Temperature

Understanding the microscopic ionic structure and thermal properties of the NaCl-CaCl_(2) mixture is of great importance for improving its photothermal energy conversion efficiency.However,the measured values of thermophysical parameters are affected by the processes near the phase transition temperature,and the measured values often change abruptly.Classical and first-principles molecular dynamics studies have recently been performed to determine the thermal properties of molten salts,but such simulations for binary molten salts including NaCl-CaCl_(2) are still rare and limited to a range above the phase transition temperature(786.0 K),and the deviations from the measurements are still large.In this study,the molecular dynamics method based on the trained deep potential is used to systematically predict the variations of the ionic structure,phonon density of state,density and thermophysical properties including heat capacity,thermal conductivity,and diffusivity,and Prandtl number of the binary chloride system of NaCl-CaCl_(2) in a wide temperature range(600-1000 K)above the phase transition temperature.The variations and correlations of the properties(especially thermal diffusivity and Prandtl number)with temperature are deduced.It is found that an increase in temperature enhances ionic vibration,thus increasing the specific heat capacity.An increase in temperature weakens the interaction and vibrational transfer between ions,and hence the thermal conductivity tends to decrease.As the temperature increases,the heat capacity increases,while the density,thermal conductivity,thermal diffusion coefficient,and Prandtl number of the system all decrease.In general,the properties obtained by applying the deep potential trained in this work reflect the experimental values more accurately than the classical and first-principles molecular dynamics simulations.

Corrosion evaluation and resistance study of alloys in chloride salts for concentrating solar power plants

Thermal energy storage(TES)systems based on molten salt are widely used in concentrating solar power(CSP)plants.The investigation of the corrosion behavior of alloy materials in molten salt is crucial for the correct selection of alloy materials and the design of TES systems.In this study,the corrosion behavior of 304,310S,316,and In625 alloys in molten chloride salts(27 mol%NaCl-22 mol%KCl-51 mol%MgCl,)was investigated.The evolution of mass loss of the alloy samples with corrosion time and temperature and the analysis of the experimental results by scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)revealed the corrosion mechanism of the alloy samples in molten chloride salts.The main factors affecting the corrosion of the alloy samples were further analyzed.It was found that the loose multi-layer corrosion was formed on the surface of the corroded alloy samples with the increase in corrosion degree.Moreover,the experimental results.showed that Mo played a positive role in improving the corrosion resistance of the alloy samples because the presence of Mo could inhibit the outward diffusion of alloying element Cr.This work enriches the molten salt corrosion database and provides a reference for the selection of alloy materials for TES systems with potential application in CSP plants.

Current efficiency of recycling aluminum from aluminum scraps by electrolysis

Extracting aluminum from aluminum alloys in AlCl3-NaCl molten salts was investigated. Al coating was deposited on the copper cathode by the method of direct current deposition using aluminum alloys as anode. The purity of the deposited aluminum is about 99.7% with the energy consumption of 3-9 kW＆#183;h per kg Al, and the current efficiency is 44%-64% when the deposition process is carried out under 100 mA/cm2 for 4 h at 170 ＆#176;C. The effects of experimental parameters, such as molar ratio of AlCl3 to NaCl, cathodic current density and electrolysis time, on the current efficiency were studied. The molar ratio of AlCl3 to NaCl has little effect on the current efficiency, and the increase of deposition temperature is beneficial to the increase of current efficiency. However, the increase of current density or electrolysis time results in the decrease of current efficiency. The decrease of current efficiency is mainly related to the formation of dendritic or powder deposit of aluminum which is easy to fall into the electrolyte.

Effects of Different Carbon Sources and NaBr-KCl on Synthesis of Ti(C,N)

Ti（ C, N） was synthesized with the starting materials of 76. 9% titania white and 23. 1% carbon black （graphite or activated carbon ）, or 40% titania white and 60% amylum, with or without 10% NaBr - KCl, dry moulding and carbon embedded firing at i 300 ℃ and 1 400 ℃ for 3 h, respectively. Phase composition and microstructure of the synthesized Ti （C, N） were analyzed by XRD, SEM and EPMA. Effects of different carbon sources and NaBr-KCl on the synthesis of Ti（ C, N） were investigated. The results show that： （1） Ti （C, N） can be synthesized by using carbon black, graphite, activated carbon or amylum as carbon source separately; （2） Additive NaBr - KCl is more favorable for accelerating the carbothermal reduction reaction using carbon black or amylum as carbon source; （3） In the presence of NaBr - KCl, particle size of the synthesized Ti（ C, N） is 5 -8μm using carbon black as carbon source fired at 1 300 ℃ for 3 h, while that is only 1 - 3 μm using graphite, activated carbon or amylum fired at 1 400 ℃ for 3 h.

Experimental and Simulation Study on Enhancing Thermal Energy Storage and Heat Transfer Performance of Ternary Chloride Eutectic Salt by Doping MgO Nanoparticles

Molten salt-based nanofluids exhibit more efficient heat storage and transfer performance than the same pure base molten salt(BS).In this work,nanofluids were prepared by dispersing nano-MgO in chloride BS(NaCl:CaCl_(2):MgCl_(2)=53:15:32,mole fraction)to improve its thermophysical properties,and the improvement mechanism was explored by molecular dynamics(MD)simulation.Among all the nanofluids,the nanofluid doped with 2.5%(mass fraction)20-nm Mgo has the best thermal property,with its specific heat capacity Cp increased by 38.2%.After heating at 600℃ for 1000 hours,the heat storage performance of the nanocomposite samples did not deteriorate.The analysis of microstructures by MD shows that there exists a semi-solid liquid layer at the interface between nano-MgO and the molten salt due to the strong interactions between nanoparticles and molten salt.It contributes to enhancing the thermal storage capacity of nanofluids.The number density and specific heat capacity both decrease as particle size increases.Combining the experimental and simulation result analysis,the possible mechanism of enhancing the specific heat capacity of nanofluids is revealed.The nanofluid prepared in this work can serve as potential heat storage/transfer materials in concentrating solar power systems,and the heat storage/transfer mechanism proposed in this work is also helpful for understanding the thermophysical properties of other molten salt nanofluids.

An in-situ Raman spectroscopic study on potential-pO^(2-) phase diagram of lanthanum in LiCl-KCl eutectic melt

The oxidative reaction between lanthanum trichloride and oxide ion was studied in the molten LiCl-KCl eutectic at 773 K by in-situ Raman spectroscopy using an yttria-stabilized zirconia electrode in conjunction with electrochemical methods.The formation of lanthanum oxychloride,LaOCl(s),was confirmed by studying the vibrational properties of crystalline LaOCl and X-ray diffraction analysis.The solubility product of LaOCl in the LiCl-KCl molten eutectic at 773 K is found to be pKsp(LaOCl)=7.569±0.100,by combining the results of Raman spectroscopy and potentiometric titration with the addition of barium oxide.The use of Raman spectroscopic quantitation of dissolved lanthanum ions in the system allows faster and more accurate determination of the stable phase of lanthanum as well as the solubility product of LaOCl compared with that measured by potentiometric titration only.Based on experimentally obtained pKsp and standard equilibrium potentials,the potentialpO2- phase diagram of lanthanum in the molten LiCl-KCl eutectic was reported.