惰气熔融-红外光谱法测定7LiF中的氧含量

7LiF是制备熔盐堆冷却剂7LiF-BeF2熔盐的基础原材料,其杂质含量的多少与熔盐纯度及应用性能直接相关。采用惰气熔融-红外吸收法,建立了熔盐堆用7LiF中杂质氧含量测定的新方法。考察了不同助熔剂和加热功率等条件对7LiF中氧含量的影响,找到了较好的 7LiF中氧含量测定方法。在分析功率为2200W,用银舟做助熔剂,称样量为0.1 g的条件下对7LiF试样进行了测定,氧的相对标准偏差为2.9%;加标回收率为103-110%。结果表明,本测定方法易操作,速度快,能满足7LiF生产过程中的质量控制要求,为第四代先进核能反应堆用7LiF规模化制备提供了有力的技术支持。     

FLiNaK–ThF4的微观结构及热力学性质的深度势能分子动力学研究

钍基熔盐堆是六种第四代先进反应堆之一,深入研究熔盐堆燃料的基础物性对反应堆的安全有效运行和乏燃料后处理意义重大.首先,使用深度神经网络对FLiNaKTh熔盐燃料的力场进行了深度学习,得到了高精度的力场模型.其次,系统研究了FLiNaKTh燃料的配位结构、热力学和动力学性质.径向分布函数和平均力势表明各离子对的相互作用强弱为:Th–F>Li–F>Na–F>K–F,且均随ThF₄浓度增大或升温而变弱.在燃料服役温度900 K下,FLiNaK–10 wt.%ThF₄体系中Th离子主要以[ThF_x]^4–x形式存在,Th浓度增大有利于Th离子间形成团簇,导致[Th₂F_x]^8–x和[Th₃F_x]^12–x等占比增大.模拟的扩散系数、热容和密度值与实验值吻合的很好,证明了力场的精确性,进一步预测了0～50wt.%ThF₄浓度范围和更多温度下熔盐体...     

惰气熔融-红外吸收光谱法测定镧铈稀土钢中氧含量

高品质稀土钢要求进行精确低氧含量控制,而依据现有GB/T11261-2006标准进行氧含量测定,检测结果具有较大的不准确性。本研究以具有不同镧、铈稀土元素含量的稀土钢为对象,以其氧含量精确测定为目标,基于惰气熔融-红外吸收法,开展了分析功率、助熔剂和称样量对镧铈稀土钢中氧含量分析结果的影响研究。结果表明,对于不同镧、铈元素含量的稀土钢,需要采用不同的分析方法：当稀土钢中的镧、铈含量较低时,通过降低分析功率即可较为精确的测定稀土钢中的氧含量;对于镧、铈含量较高的稀土钢,在调控分析功率（分析功率在4000W～4500W）的基础上,需同时采用锡作为助熔剂,并将助熔剂与样品比例设定为1:1（称样量为0.3g～0.6g）,即可实现氧含量的精确测定。精密度验证实验结果显示,采用本研究所建立的方法,氧含量测试结果相对标准偏差（RSD）小于8.0%;采用钢标样进行回收率实验,回收率值在97%～108%,而加标回收率略有升高的原因在于助熔剂Sn降低了合金熔点,使少量难熔氧化物中的氧得到更充分释放。本研究所建立的分析方法可准确测定不同镧、铈元素含量稀土钢中的氧含量。     

基于MgCl2-HoCl3熔盐镁直接脱除钛废料中固溶氧研究

针对现有钛脱氧方法存在成本高、效率低、金属/熔盐分离困难等问题,本研究提出了一种在MgCl₂-HoCl₃熔盐中,采用Mg作脱氧剂直接脱除钛中固溶氧的新方法。在1273 K下开展了热力学计算和实验研究,结果表明：在MgCl₂-HoCl₃熔盐中,借助Ho OCl(O(in β-Ti)+Mg(l)+HoCl₃(l)=MgCl₂(l)+HoOCl(s))的生成,有效降低了脱氧副产物MgO的活度,促进了镁深度脱氧,钛中氧含量可降低至1000×10^-6以下(甚至500×10^-6以下)。随着熔盐中HoCl₃活度的增加,钛中的氧含量降低,当HoCl₃的活度为1.0时,氧含量可降至80×10^-6左右。基于以上研究结果,本研究提出了一种新的脱氧工艺,该工艺具备成本低、效率高、金属/熔盐分离简单等优势,有望在未来实现工业化应用。     

惰性气体熔融-热导法测定硅材料中的氧

采用惰性气体熔融–热导法测定硅材料中杂质氧的含量。经试验确定了仪器的最佳分析条件:称样量为0.05～0.15g,分析功率为4 500 W,使用镍助熔剂、座坩埚;采用(30+40)s二次腐蚀方法处理助熔剂,以降低助熔剂的空白值。选择与待测试样性质类似、氧含量接近的标准物质校正仪器,氧的质量在0.01～0.30 mg之间与信号积分面积呈良好的线性,线性相关系数r=0.999 8,方法检出限为27μg/g。对氧含量不同的硅材料试样进行测定,测定结果的相对标准偏差为1.5%～3.4%(n=11),加标回收率为96.2%～99.2%。该方法操作简单快捷,测定结果准确。     

有机元素分析仪测定丙烯腈-衣康酸共聚物中衣康酸的含量

建立有机元素分析仪测定丙烯腈-衣康酸共聚物中衣康酸含量的方法。采用二甲基甲酰胺溶解、甲醇沉降纯化和灼烧的方法验证了样品纯度,用有机元素分析仪测定样品中氧的含量,通过计算氧含量得到了衣康酸的含量。采用苯甲酸建立标准工作曲线,氧的质量在30~1570μg范围内与响应信号成良好的线性关系,线性相关系数为0.999,测定结果的相对标准偏差为1.9%(n=6),加标回收率为99.1%~100.5%。该方法简单快速,准确度和精密度高,适合丙烯腈-衣康酸共聚物中衣康酸含量的快速测定。     

基于脉冲加热-红外吸收/热导法测定烧结氮化硅陶瓷材料中晶格氧含量

基于脉冲加热-红外吸收/热导法,比较分析了恒定式、斜线式及阶梯式3种功率控制升温模式在烧结氮化硅陶瓷材料氧氮含量测定中的特点。优化后选择阶梯式功率控制升温模式并设置合理的分析参数,获得了分离良好的氧氮分量峰。结合在脉冲加热熔融样品过程中特定点位取样的X射线衍射物相分析,确定了烧结氮化硅材料的晶格氧分量峰位置及含量。测试得出Yb₂O₃做助剂的烧结氮化硅陶瓷晶格氧含量为0.094%,相对标准偏差为1.6%,与此材料的热导率水平(88.61 W/m·K)相符合。本方法适用于多种非氧化物陶瓷材料中晶格氧含量的测定。     

惰性熔融-红外吸收/热导法测定高铍铍铝合金中氧氮

建立红外吸收/热导法同时测定高铍铍铝合金中氧氮的含量。称取0.03～0.04 g试样,以带盖镍囊(Φ7mm×6 mm)包裹,使用0.1 g纯铜助熔剂及0.05 g纯锡助熔剂为混合浴料,在4 500 W的分析功率下,高纯氦气氛中熔融释放气体,通过红外吸收池测定氧含量,热导池测定氮含量。对氧质量分数为0.217%～0.546%及氮质量分数为0.005 8%～0.012 0%的试样进行测定,测定结果的相对标准偏差分别为1.07%～3.00%(n=8)与4.55%～4.94%(n=8),氧的加标回收率为97.1%～103.8%,氮的加标回收率为95.9%～104.4%。该方法操作简单快捷,测定结果准确。     

高温氟化盐对熔盐堆用材料的腐蚀行为研究进展

氟化物熔盐在熔盐堆(MSR)中可用作为核燃料载体和冷却剂,其独特热物理化学性质能极大提高MSR的传热效率。但MSR高温和强腐蚀条件对材料的选择使用要求非常苛刻,特别是氟化物熔盐在高温下对结构材料的腐蚀直接关系到MSR的安全运行和使用寿命,成为制约MSR应用发展的关键。本文综述了LiF-NaF-KF(Flinak)和LiF-BeF2(Flibe)熔盐与金属合金材料、碳材料及陶瓷材料腐蚀行为方面的研究进展,对材料在不同条件下腐蚀行为的机理进行了分析。研究发现,应用于MSR的高镍基合金及石墨材料存在着高温腐蚀性及机械性能差等弱点。未来新型高镍基合金、C/C复合材料及新型陶瓷材料(SiC及其复合材料、其他陶瓷材料)有望在氟化物熔盐体系中获得应用,并最终解决MSR用材料的困惑,实现MSR快速工业化发展。     

惰气熔融-红外法测定镍钛合金中的氧含量

针对镍钛(NiTi)合金中的氧含量进行研究,建立了惰气熔融-红外吸收法测定NiTi合金中氧含量的新方法。研究了不同助熔剂、称样量、分析功率、分析时间及比较器水平对测定结果的影响。确定采用镍做助熔剂,分析功率为4.0至5.5kW,分析时间为30s,比较水平为2的条件对NiTi合金中氧含量进行测定。惰气熔融-红外法测定NiTi合金氧含量相对标准偏差为1.8%,对标准样品的测定结果与标准值基本相符。方法操作简单,分析速度快,能满足生产要求,对工艺研究和产品质量控制具有积极意义。     

Determination of Gibbs energy of formation of LiThF5, LiTh2F9, and LiTh4F17 in Li-Th-F system by using solid electrolyte galvanic cell

Journal of Solid State Electrochemistry - The LiF-ThF4 system has been considered as reference fuel solvent for molten salt reactor. The high-temperature interaction of LiF-ThF4 leads to formation...     

A radioactive tracer dilution method to determine the mass of molten salt

A new technique for molten salt mass determination, termed radioactive tracer dilution, that uses ²²Na as a tracer was validated at bench scale. It has been a challenging problem to determine the mass of molten salt in irregularly shaped containers, where a highly radioactive, high-temperature molten salt was used to process nuclear spent/used fuel during electrochemical recycling (pyro-processing) or for coolant/fuel salt from molten salt reactors. A radioactive source with known activity is dissolved into the salt. After a complete mixture, a small amount of the salt is sampled and measured in terms of its mass and radioactivity. By finding the ratio of the mass to radioactivity, the unknown salt mass in the original container can be precisely determined.

     

Reactor physic and reprocessing scheme for innovative molten salt reactor system

The molten salt reactor is one of the six concepts retained by the Generation IV forum in 2001. Based on the MSRE and MSBR concepts developed by ORNL in the 60s which involve a liquid fuel constituted of fluorine molten salt at a temperature close to 600 °C, new developments with innovative approach and technology have been realized which contribute to strongly improve the concept. The thorium breeder potentiality is closely related to the use of a liquid fuel which is able to be periodically treated. A reprocessing scheme has been established to treat used fuel by extraction of fission products. According to the Gen IV philosophy for closed cycle nuclear reactor, the actinides are sent back in the reactor core. In this way, the wastes radiotoxicity is strongly decreased and the use of natural resource is optimized. This paper describes an innovative reactor concept, the TMSR-NM (non-moderated thorium molten salt reactor), from the nuclear physic point of view and the different steps involving in the reprocessing scheme from the chemical point of view.     

Heat-transport properties of molten fluorides: Determination from first-principles

The construction of an interaction potential for mixtures of LiF, NaF, KF and ZrF₄ on a purely first-principles basis is described. Many-body interactions are included via a polarization term. The predictions of the heat-transfer properties of two mixtures, LiF-NaF-KF (FLiNaK) and NaF-ZrF₄, are then compared with experimental values. Values for the densities, thermal expansions, heat capacities and viscosities are compiled into figures of merits in order to compare the suitability of those molten salts to serve as primary or secondary coolants in a nuclear reactor.     

Materials corrosion in molten LiF-NaF-KF salt

Corrosion tests of high temperature alloys, Hastelloy-N, Hastelloy-X, Haynes-230, Inconel-617, and Incoloy-800H were performed in molten fluoride salt, FLiNaK (LiF-NaF-KF:46.5-11.5-42 mol%) with the goal of understanding the corrosion mechanisms and ranking these alloys for their suitability for molten fluoride salt heat exchanger and thermal storage applications. The tests were performed at 850 °C for 500 h in sealed graphite crucibles under an argon cover gas. Corrosion was noted to occur predominantly by dealloying of Cr from the alloys, an effect that was particularly pronounced at the grain boundaries of these alloys. Weight-loss due to corrosion generally correlated with the initial Cr-content of the alloys, and was consistent with the Cr-content measured in the salts after corrosion tests. Two Cr-free alloys, Ni-201 and Nb-1Zr, were also tested. Ni-201, a nearly pure Ni alloy with minor alloying additions, exhibited good resistance to corrosion, whereas Nb-1Zr alloy exhibited extensive corrosion attack. The graphite crucible may have accelerated the corrosion process by promoting the formation of carbide phases on the walls of the test crucibles, but did not alter the basic corrosion mechanism.     

用于部分氧化甲烷制合成气的铈基氧载体性能表征

将稀土氧化物CeO2中的晶格氧用于熔融盐体系下甲烷部分氧化制取合成气的新方法,采用浸渍法制备了负载型铈基氧载体,利用XRD、O2-TPD、H2-TPR分析手段对氧载体进行了表征.在甲烷气氛下进行了CeO2的热重实验.在熔融盐反应器中分别考察了添加1%TiO2和MgO两种不同助剂对10?O2-Al2O3负载型氧载体反应性能的影响.结果表明,CeO2容易失去晶格氧被还原为低价态铈的氧化物,同时把甲烷部分氧化成H2和CO,有着良好的循环使用性能.助剂的添加能够明显改善氧载体的反应活性,其中以添加MgO比较理想.     

Nanocomposite phase change materials based on NaCl–CaCl2 and mesoporous silica

The synthesis of phase change materials based on NaCl–CaCl₂ molten salt mixture and mesoporous silica was investigated. The influence of mesoporous silica porosity and salt concentration on the thermal energy storage properties of the resulting materials is discussed. The nanocomposite samples were characterized by X-ray diffraction, differential scanning calorimetry, infrared spectroscopy, thermogravimetry, scanning electron microscopy and X-ray photoelectron spectroscopy. The mesoporous silica was found to act as a reactive matrix for the molten salts. Composite samples with up 95% wt. salt can be obtained and used as shape-stabilized phase change materials. The materials have heat of fusion values of up to 60.8 J g^?1 and specific heat capacity between 1.0 and 1.1 J g^?1 K^?1. The samples exhibit thermal stability up to 700 °C and can be used for high-temperature thermal energy storage through both latent and sensible heat storage mechanisms.

     

Evaluating physical properties of molten salt reactor fluoride mixtures

In the last years, interest in the use of high-temperature molten fluoride salts as fluid fuels and coolants in nuclear power systems has been increasing. The comprehensive information on the properties of molten fuel and coolant salts is necessary for development of new designs. Experimental data on physical properties of some prospective molten salt mixtures of Li, Na, Be, Zr fluorides containing fertile and fissile materials as well as soluble fission products are unknown. At the first stage of the conceptual development estimation of the required properties from the known experimental data can be useful for selection of suitable molten salt compositions. In this paper the approaches for estimation of the physicochemical properties such as density (ρ), dynamic viscosity (η), isobaric heat capacity (c_p), and thermal conductivity (λ) for molten salt fluoride mixtures are proposed. The calculation algorithm was based on the additivity principle for the properties (P_x) of multi-component molten salt mixtures, which can be found from the relationship P_x = ΣN_iP_i. Here N_i and P_i denote mole fraction and corresponding property of individual molten salts or their binary mixtures as constituents of the more complex systems. The empirical expressions connecting the property with molar volume and molecular mass of selected fluoride compositions are also derived and tested. Estimated values are compared with each other and available experimental data.     

Identification of Superoxide O2- during Thermal Decomposition of Molten KNO3-NaNO2-NaNO3 Salt by Electron Paramagnetic Resonance and UV-Vis Absorption Spectroscopy

On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in concentrated solar power system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species O₂^2- and O₂^- were considered as intermediates in molten KNO₃-NaNO₃ while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UVVis instrument and a commercial electron paramagnetic resonance were utilized to supply evidence for the formation of superoxide during a slow decomposition process of heat transfer salt (HTS, 53 wt% KNO₃/40 wt% NaNO₂/7 wt% NaNO₃). It is found that the superoxide is more easily generated from molten NaNO₂ compared to NaNO₃, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO₂ or KO₂, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO₂ and NaNO₃ are also obtained and compared with that of HTS.