SOM电解法对氟盐冷却剂进行在线净化的研究

熔盐堆氟盐冷却剂在服役周期内应保持较高的纯度以维持其对堆结构材料良好的相容性。氟盐中的O^2−以及Cr^3+、Fe^2+、Ni^2+等过渡金属离子可能增强熔盐腐蚀性,并导致液态核燃料形成难溶氧化物进而影响堆的安全性。通过在线净化的方式去除这些有害杂质可提高氟盐冷却剂的服役周期和增强反应堆的安全性。基于固体氧化物膜(Solid Oxide Membrane,SOM)电解法的在线净化方法可有效去除上述有害杂质,从热力学和动力学的角度分析了各种影响SOM电解脱氧净化的因素。600℃下的SOM电解脱氧试验结果表明:通过SOM(Zn)阳极和石墨阴极电解,可将氟盐中的O^2−降低至100μg·g^−1以下,将Cr^3+、Fe^2+、Ni^2+等过渡金属离子降低至10μg·g^−1以下,显示了SOM电解法在氟盐冷却剂在线净化方面具有很好的应用前景。

LiF-BeF2熔盐微观结构及扩散特性的分子动力学研究

LiF-BeF2熔盐作为熔盐堆的冷却剂及核燃料溶剂近年来备受关注,其扩散行为与核燃料的相容性和结构材料的腐蚀性密切相关。采用Car-Parrinello分子动力学模拟研究了LiF-BeF2熔盐的微观结构及基于此结构的扩散行为。研究结果表明Be2+具有较强的络合能力,易形成中性网络聚合体,且其数量随温度的增加而减少;液态LiF-BeF2熔盐中除了包含聚合体,还包含游离的F^-、Li^+、BeF3^-和BeF4^2-,而非完全游离的F^-、Li^+和Be^2+。基于此微观结构获得的自扩散系数及电导率与实验结果吻合较好,且电导率随温度变化符合Arrhenius模型,而不是目前文献认为的无限稀释溶液的线性模型。

ESR signals from silk fabrics irradiated by UV-rays

ESR studies were done on UV-ray irradiated silk fabric samples at room temperature. Different types of UV lamps were used and similar ESR signals were observed. The results indicate that UV-rays can produce free radicals for graft-copolymerization of monomer onto silk fibers without external additives or co additives, Also, radicals in silk fabrics irradiated by UV-rays are purer than that irradiated by γ-rays. The study suggests that UV-lights may be a better tool to improve properties of silk fabrics by grafting monomers onto the polymer chains.

Preparation and characterization of proton exchange membranes from polystyrene grafted poly(vinylidene fluoride) powder

Proton exchange membranes(PEMs)were prepared in three steps:grafting of polystyrene onto PVDF powder using pre-irradiation graft polymerization technique,processing the grafted PVDF powder into membranes of around 50-μm thickness,and sulfonating them with cholorosulfonic acid to form poly(vinylidene fluoride)-g-poly(styrene sulfonic acid)membranes.Kinetics of the graft polymerization was studied.The existing of polystyrene side-chains in the grafted PVDF powders,and PSSA groups in PEMs,were proved by FT-IR.Properties of the PEMs,i.e.the ion exchange capacity,water uptake,proton conductivity,thermal property and oxidative stability, were characterized.Dependence of properties on the degree of grafting was investigated,too.

Experimental Investigation and Thermodynamic Modeling of the NaCI-NaNO3-Na2SO4 Ternary System

Molten salts as heat transfer and storage materials have been used to nuclear energy and concentrated solar power（CSP） applications. In this work, the system of molten salt mixture based on thermodynamic principles was designed as thermal energy storage（TES） materials. The substitutional solution model can be employed to describe the Gibbs energies of all liquid phase. Thermodynamic model parameters for the NaCl-NaNO3-Na2SO4 subsystems were conducted by thermodynamic evaluation and optimization based on experimental phase-equilibria data. Thus, a set of self-consistent thermodynamic database was eventually obtained to reliably calculate the whole phase diagram and thermodynamic properties for the NaCl-NaNO3-Na2SO4 ternary system. The results manifest that the eutectic point of theternary system located at T=280 ℃ and XNaCl=8.4%, XNaNO3=86.3% and xNa2SO4=5.3%. Moreover, the results predicted were verified experimentally using differential scanning calorimetry（DSC） and the agreement between the measured value[T=（287±2） ℃] and predicted value（T=280 ℃） was satisfactory. Thus, the thermodynamic calculation method will be used to design and develop novel molten salt mixture as thermal energy storage materials.

Thermodynamic Evaluation of NaF-MFn（M=Be, U, Th） Systems for Molten Salt Reactor

The phase diagrams of NaF-BeF2, NaF-ThF4 and NaF-UF4 systems were assessed based on thermodynamic principles, and diverse thermodynamic models were adapted to different systems. Associate solution model （ASM） was used to describe the Gibbs energies of liquid phase of the NaF-BeF2 system, whereas other systems（NaF-ThF4 and NaF-UF4） were treated with the substitutional solution model（SSM） and intermediate compounds were described as stoichiometric compounds according to the Neumann-Kopp rule. All the thermodynamic model parameters were optimized by the least squares procedure until good coincidence was achieved between the calculated results and the experimental data. The derived thermodynamic parameters will be merged into the NaF-BeF2-ThF4-UF4 database to develop the thorium molten salt reactor（TMSR） project.

Thermodynamic and Phase Diagram Modeling of CsF-MF4（M=U, Th） Systems

Phase diagrams for the CsF-UF4 and CsF-ThF4 systems were modeled in the present work through computational thennodynamics. The associate solution model with various complex species（CsMFs, Cs2MF6 and Cs3MF7; M=Th, U） was used to thermodynamically describe the binary molten salts. A total of ten intermediate phases were treated as stoichiometric compounds with their Gibbs energies modeled according to the Neumann-Kopp rule. All these model parameters were optimized by the least squares procedure until good coincidence was achieved between the calculated results and most of the experimental data. The derived thermodynamic parameters will be merged into the multicomponent CsF-LiF-BeF2-ThF4-UF4 database for analyzing physicochemical behavior of CsF in the fuel salt of the molten salt breeder reactor.

Thermodynamic Modeling of KF-CrF3 Binary System

A comprehensive thermodynamic model of KF-CrF3 system was established. The intermediate phases K2Cr5F17, KCrF4, K2CrF5 and K3CrF6 were described by the stoichiometric compound model and the liquid phase by associated solution model. All the model parameters were optimized by the experimental phase equilibria data as- sisted by the first-principles prediction within the framework of the calculation of phase diagram（CALPHAD） me- thod. It is demonstrated that the calculated results are fairly consistent with the experimental data, thus we obtained a set of self-consistent and reliable thermodynamic parameters which could well describe the phase equilibria and thermodynamic properties of KF-CrF3 system.