Gd_2O_3-UO_2芯块烧结密度影响因素研究

Gd_2O_3-UO_2可燃毒物燃料芯块的烧结密度是个重要指标,是质量控制的主要项目之一。为此研究了Gd_2O_3粉末预处理、添加剂、混合方式和时间、烧结气氛、烧结温度和时间等工艺参数对Gd_2O_3质量百分含量分别为0,3％,7％,10％的Gd_2O_3-UO_2芯块最终密度的影响。结果指出:预处理有利于Gd_2O_3分布均匀;添加草酸铵能有效地调整芯块密度;烧结温度1750℃为宜。选用了合适的工艺参数,制备出了密度为理论密度的93.5％～96.5％,且均匀性和微观结构等均满足设计要求的辐照考验用Gd_2O_3-UO_2芯块。     

添加剂对UO2烧结动力学的影响

本文求出了含 Nb_2O_5、Cr_2O_3和 Gd_2O_3的三种掺杂 UO_2芯块的晶粒生长方程和晶界移动激活能。激活能大小相应为1.88×10~5,2.01×10~5和2.59×10~5J/mol.讨论了添加剂对 UO_2燃料芯块烧结动力学以及晶粒长大动力学的影响。     

Gd_2O_3-UO_2芯块烧结密度影响因素研究

Gd_2O_3-UO_2可燃毒物燃料芯块的烧结密度是个重要指标,是质量控制的主要项目之一。为此研究了Gd_2O_3粉末预处理、添加剂、混合方式和时间、烧结气氛、烧结温度和时间等工艺参数对Gd_2O_3质量百分含量分别为0.3％,7％,10％的Gd_2O_3-UO_2芯块最终密     

Gd_2O_3-UO_2芯块的均匀性及微观结构研究

用光学显微镜、X射线波谱仪和能谱仪、扫描电镜-图像处理、X射线衍射仪和图像分析仪分析了不同条件制备的0～10wt％Gd_2O_3-UO_2芯块的微观结构、Gd_2O_3在芯块中的分布均匀性、固溶体点阵常数,计算出了理论密度。研究了Gd_2O_3粉末颗粒大小和含量、混料方式、烧结温度和时间、烧结气氛与Gd_2O_3-UO_2芯块的微观结构和Gd_2O_3分布均匀性的关系。     

Gd_2O_3-UO_2芯块的均匀性及微观结构研究

用光学显微镜、X射线波谱仪和能谱仪、扫描电镜-图像处理、X射线衍射仪和图像分析仪分析了不同条件制备的0～10wt％Gd_2O_3-UO_2芯块的微观结构、Gd_2O_3在芯块中的分布均匀性、固溶体点阵常数,计算出了理论密度。研究了Gd_2O_3粉末颗粒大小和含量、混料方式、烧结温度和时间、烧结气氛与Gd_2O_3-UO_2芯块的微观结构和Gd_2O_3分布均匀性的关系。     

烧结Gd_2O_(3)-UO_2芯块吸湿性研究

用热重法测量加热Gd_2O_3-UO_2烧结芯块,研究其吸湿性。实验结果证明:高密度、低开口孔隙率(≤0.2％)的Gd_2O_3UO_2芯块暴露在相对湿度为40％～90％空气中吸附的水是可以忽略不计的,并在室温真空条件下就很容易除去;具有特别高开口孔隙率(2％)的芯块中的吸附水可以通过线性升温至150℃保温1.5 h以上除去;而芯块中“茶壶状”或称     

Gd_2O_3-UO_2可燃毒物反应性效应研究

本文介绍了水-水零功率堆均匀栅格中,利用周期法和脉冲中子源法测量Gd_2O_3—UO_2毒物燃料棒反应性效应的几个实验结果。给出了在水铀体积比分别为3.27、2.74和2.14的三种堆芯栅格中,Gd_2O_3浓度分别为0.5W/0、0.8W/0和5.0W/0的Gd_2O_3—UO_2毒物燃料棒沿着堆芯经向方向单棒反应性价值和不同位置的反应性饱和浓度;同时给出了在水铀体积比为3.27的堆芯栅格中,Gd_2O_3—UO_2毒物燃料棒之间的反应性干涉效应以及控制棒对这类可燃毒物反应性效应影响的实验结果。本实验还研究了Gd_2O_3微粒大小及Gd_2O_3微粒表面镀钼保护层对钆可燃毒物反应性价值的影响,并给出了相应的实验结果。     

UO_2-Er_2O_3燃料芯块的烧结工艺研究

对UO_2-Er_2O_3可燃毒物燃料芯块的烧结工艺进行研究。试验表明:烧结过程中选择生坯密度在55%~60%理论密度的生坯芯块,在1700~1750℃,H2气氛中烧结2~3 h,可得到完整度、密度、晶粒尺寸等性能满足要求的燃料芯块。     

可控孔隙UO_2燃料芯块

UO_2燃料芯块的微观结构对燃料的堆内尺寸行为起决定性作用。采用U_3O_8添加剂可改善芯块微观结构,但同时使芯块密度下降,开口孔隙度增加进而导致吸湿加剧。因此,必须采用烧结性良好的UO_2粉末和合适的成型烧结条件以使开口孔隙度和细孔隙度降至最低。     

烧结Gd_2O_3-UO_2芯块吸湿性研究

用热重法测量加热Gd_2O_3-UO_2烧结芯块,研究其吸湿性。实验结果证明:高密度、低开口孔隙率(≤0.2％)的Gd_2O_3-UO_2芯块暴露在相对湿度为40％～90％空气中吸附的水是可以忽略不计的,并在室温真空条件下就很容易除去;具有特别高开口孔隙率(2％)的芯块中的吸附水可以通过线性升温至150℃保温1.5h以上除去;而芯块中“茶壶状”或称“墨水瓶状”深孔中的水及制备过程中带进的强力化学结合水要到400℃以上才能释放。除气后的Gd_2O_3-UO_2芯块中含水量远低于10μg/g,满足芯块含水量不超过15μg/S的技术要求。可以避免由于芯块水分含量超标致使锆合金包壳管氢脆所造成的燃料棒破损。     

Vaporization and Surface Ionization of LaC2, CeC2, PrC2, NdC2, ThC2 and UC2

The Langmuir vaporization and the surface ionization of LaC₂, CeC₂, PrC₂, NdC₂, ThC₂ and UC₂ from a heated graphite filament have been studied mass spectrometrically. It was found that there were present small amounts of neutral and ionic metal dicarbide molecules in addition to neutral and ionic metal atoms in the LaC₂, CeC₂, PrC₂, ThC₂ and UC₂-C systems with the exception of NdC₂-C, where neither neutral nor ionic metal dicarbide molecules were observed. The reason for this exceptional behavior of the NdC₂-C system is explained by the very small vaporization coefficients, as estimated from the measurements of neutral MC₂/M ratios and ionic MC₂/M ratios.

From the measurements of the heats of vaporization, it was surmised that the ionization potential of Th measured by the surface ionization comparison technique might be too high.     

UO22+在羟基磷灰石上的吸附

以羟基磷灰石（HA）作骨体外模型结合计算机模拟的方法,研究了UO₂²⁺在HA上的吸附行为以及不同种类的螯合剂对其吸附行为的影响。结果表明,15 min后HA对UO₂²⁺的吸附达到平衡,HA颗粒形貌未发生明显改变,吸附过程符合拟二级动力学方程;乙二胺四乙酸（EDTA）和二乙基三胺五乙酸（DTPA）对HA上UO₂²⁺的促排作用类似,能与UO₂²⁺螯合形成大量的络合离子从而达到促排的目的,但会对骨骼无机相表面造成损伤;柠檬酸对吸附在HA上的UO₂²⁺具有较强的解吸作用,但高浓度的柠檬酸会造成HA颗粒形貌显著变化,因此不适合作为铀的促排剂;抗坏血酸对UO₂²⁺在HA上的解吸没有作用,而氨基三乙酸（NTA）会导致HA对铀的吸附率增加。     

Thermal Conductivity of ThO2-UO2 System

The thermal diffusivity of the ThO₂-UO₂ system in solid solution was measured by laser pulse method at temperatures ranging from 20° to 500°C. Reproducibility of the data was confirmed to be within 3%. The compositions of the samples were ThO₂, ThO₂-1%UO₂, ThO₂-5%UO₂ and ThO₂-10%UO₂.

The thermal conductivity was calculated from measured thermal diffusivity data and the specific heat data available in literature and corrected to zero porosity by using Loeb's equation, in which the shape factor is unity.

The values on ThO₂ thus obtained agreed very well with the data found in literature, throughout the range of temperature of the experiments. The thermal conductivity of ThO₂, ThO₂-1%UO₂, ThO₂-5%UO₂ and ThO₂-10%UO₂, at 20°C, were 0.0312, 0.0288, 0.247 and 0.0184 cal·cm/sec· °C·cm², respectively.     

Study on Redox Equilibrium of UO2 2+/U2 + in Molten NaCl-2CsCl by UV-Vis Spectrophotometry

In order to enhance the understanding of the redox equilibriums of uranyl ions in molten NaCl-2CsCl eutectic salt UV-Vis absorption spectrophotometry measurements were performed for UO₂ ²⁺ in molten NaCl-2CsCl at 923 K under simultaneous electrolytic control of their ratio. A prominent absorption band at 395 nm was assigned to UO₂ ⁺, and its molar absorptivity was determined to be 832±27 mol^-1·l·cm^-1. From the dependence of the rest potential of the melt on the spectrophotometrically determined ratio of [UO₂ ²⁺]/[UO₂ ⁺], the standard redox potential of the couple UO₂ ²⁺/UO₂ ⁺ was determined to be ?0.903±0.007 V vs. Cl₂/Cl^—.     

Vapor Species over Na2O-B2O3-SiO2-Cs2O Glass

Methods for suppression and control of the axisymmetric vertical positional instability are described on the basis of conceptural design studies with the International Tokamak Reactor (INTOR). The shell effect is well known to be useful for suppression of the fast instability. Here shell structures are presented and their usefulness is assessed. Included in the assessments are required modellings of the plasma current for determination of mutual inductances between the plasma and the inductive components around it. Three kinds of models are described and their features are compared to the shell effect. Two kinds of simplified reactor structures are described and studied by comparing them with some control characteristics of the slow instability by a pair of control coils. Their structures are selected so as to result in different shell effects between them, and are consequently found to produce different capacities of power supply, too.