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.     

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.     

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。     

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.     

Heats of Vaporization of UO2 and UO from UO2

In an earlier paper, a stochastic model of a power reactor has been proposed by the present author on the premise that the coolant-flow through a core is usually accompanied by random variations in the flow-rate, which are eventually largely responsible for the internal reactivity fluctuations.

In the present work, this model is extended to three different reactor systems: (a) where there exists a relaxation process corresponding to the effect of buoyant flow; (b) where a control or fuel element vibrates randomly, due to coolant flow-rate fluctuations; (c) where there are fluctuations in the inlet temperature with a non-white spectrum.

The noise spectra are derived for various state quantities with use made of the Langevin procedure. The theory is illustrated by referring chiefly to the neutron noise spectra, and comparing with the results of observations.

It is shown that the noise sources in question contribute significantly to the spectra, as compared with a low frequency component due to an inherent noise source in the coolant flow. In particular, a strong resonance peak of the spectra arises from the coupling between the random mechanical vibrations and coolant the flow-rate fluctuations.     

钯催化H2O2分解的机制探讨

高放废物（HLW）处置库近场地下水的辐解能够产生H₂O₂,其被裂变产物合金颗粒（ε-颗粒）的催化分解属于多相表界面反应。本工作选用钯粉模拟ε-颗粒,采用高压反应釜研究体系总压和H₂分压对反应的影响,并按一级动力学模型拟合实验数据。添加HO·的捕获剂和淬灭剂的实验证明无H₂反应过程中存在HO·的生成步骤。钯的催化活性及形态变化与反应时间的关系表明,产物氧吸附在钯的表面对反应具有毒化作用。通过持续监测滤液中H₂O₂浓度的变化,发现溶液中存在类似于Haber-Weiss的反应持续消耗H₂O₂。推导出钯对H₂O₂分解的机制过程和影响因素,为处置库的安全评估提供基础数据。     

CO_2呼气试验和H_2呼气试验的临床应用

呼气试验简单无创、灵敏度高、特异性较强,受到研究者的关注。本文介绍了CO__2呼气试验和H_2呼气试验的临床应用。CO_2呼气试验的主要应用有胃幽门螺杆菌检测、肝功能检测、胃排空检测、胰岛素抵抗检测和胰腺外分泌测定等。H_2呼气试验可用于诊断乳糖吸收不良和检测小肠细菌过度生长。随着进一步的研究,呼气试验因其高灵敏度,非侵入性,有望应用于更多疾病的诊断。     

First-principles study of UC2 and U2C3

The electronic structure and mechanical properties of UC₂ and U₂C₃ have been systematically investigated using first-principles calculations by the projector-augmented-wave (PAW) method. Furthermore, in order to describe precisely the strong on-site Coulomb repulsion among the localized U 5f electrons, we adopt the generalized gradient approximation +U formalisms for the exchange-correlation term. We show that our calculated structural parameters and electronic properties for UC₂ and U₂C₃ are in good agreement with the experimental data by choosing an appropriate Hubbard U = 3 eV. As for the chemical bonding nature, the contour plot of charge density and total density of states suggest that UC₂ and U₂C₃ are metallic mainly contributed by the 5f electrons, mixed with significant covalent component resulted from the strong CC bonds. The present results also illustrate that the metal–carbon (UC) bonding and the carbon–carbon covalent bonding in U₂C₃ are somewhat weaker than those in UC₂, leading to the weaker thermodynamic stability at high temperature as observed by experiments.     

乙二胺改性壳聚糖磁性微球吸附Hg

采用化学交联-种子溶胀法制得乙二胺改性壳聚糖磁性微球(EMCS),考察了其对水溶液中Hg2 和UO22 的吸附性能。结果表明,EMCS粒径为50-80μm,氧化铁质量分数(w)为16%,该吸附剂在pH<2.5时可选择性吸附Hg2 和UO22 ,吸附容量随pH升高而增加;其吸附等温线用Langmuir方程拟合为:ceq/Qeq=0.440 5ceq/Qm 0.584 0(Hg2 ,r=0.996 0),ceq/Qeq=0.525 6ceq/Qm 1.343 4(UO22 ,r=0.990 6);饱和吸附容量Qm分别为2.27,1.90 mmol/g,高于磁性壳聚糖微球MCS和壳聚糖微球CS;其吸附动力学可用Lagerg-ren方程拟合为:lg(Qeq-Q)=0.361 2-0.015 5t(Hg2 ,r=0.982 1),lg(Qeq-Q)=0.302 7-0.011 2t(UO22 ,r=0.992 5);对Hg2 ,UO22 的吸附速率常数(kad)分别为0.036,0.026 min-1;EMCS可用1 mol/LH2SO4再生,脱附率大于90%,有良好的重复使用性。