Thermal Expansion and Thermal Conductivity of Cesium Uranates

Two kinds of cesium uranates, which are often predicted by thermochemical calculations to be formed in irradiated oxide fuels with high oxygen potentials, were prepared from U₃O₈ and Cs₂CO₃ to determine the thermal expansions and the thermal conductivities. The lattice parameters of tetragonal Cs₂UO₄ and monoclinic Cs₂U₂O₇ were measured by the high-temperature X-ray diffraction method as a function of temperature. The linear thermal expansions of Cs₂UO₄ and Cs₂U₂O₇ obtained from the temperature dependencies of the lattice parameters were 1.2% and 1.1% from room temperature to 973 and 1,073K, respectively. The thermal diffusivities of Cs₂UO₄ and Cs₂U₂O₇ were measured on the disk-shaped samples by the laser flash method as a function of temperature. The thermal conductivities were evaluated from the measured thermal diffusivities and the bulk densities, and the specific heat capacity available in literature. The thermal conductivity of Cs₂UO₄ corrected for 100%TD was 1.2W/m·K at 980K and that of Cs₂U₂O₇ was 0.94W/m·K at 1,093K, which are about 30% and 27% of that of UO₂, respectively.     

小型NaK热真空电磁泵热控措施影响分析

热真空电磁泵是一种在热真空环境条件下使用的高温电磁泵，换热途径的缺失使得设备整体温度很高，高温会使结构和功能材料的性能剧烈下降。本文采用数值计算方法对中国原子能科学研究院研制的小型NaK热真空电磁泵内构件温度分布进行了计算。结果表明：在泵沟外壁采用真空隔热屏、气密腔室内外壁喷涂黑体涂层的热控措施行之有效，降低了设备内构件尤其是励磁线圈的温度，提高了设备的使用寿命。     

核电厂温排水热影响研究的建议

核电厂温排水的热污染问题已引进越来越多的关注。本文介绍了增温速率对鱼类的热忍耐能力的潜在影响的研究现状,建议现阶段我国应开展变温速率对水生物热忍耐能力影响的相关研究。     

Thermal Diffusivities and Thermal Conductivities of UO2-Gd2O3

Thermal diffusivities of samples of UO₂ and UO₂ doped with 3, 5, 7 and 10 w/0 Gd₂O₃ were measured over the temperature range of 298~2,023 K by a laser flash method. Then thermal conductivities were calculated from them. The thermal conductivity decreased with increasing Gd₂O₃ content at low temperatures, while it was independent of Gd₂O₃ content at high temperatures. An expression of the thermal conductivity was proposed for (U, Gd)O₂ solid solution as a function of Gd₂O₃ content and temperature by applying Klemens' model.     

热解吸法评价铒氢化物晶体结构的热稳定性

文章介绍了铒氢化物的热力学特性研究进展,实验测定了铒三氘化物的热解吸谱,建立了热解吸谱峰与晶体精细结构的对应关系,发现并确认了铒氘化物中氘原子占据CaF₂型面心立方结构（fcc）八面体间隙（β_Oct）和四面体间隙位置（β_Tet）时的氘释放峰。采用Redhead模型计算得到了γ+β相、β_Oct相和β_Tet相铒氘化物解吸氘的表观活化能,其值分别为（178.3±3.0）、（204.5±1.2）和（309.2±0.6） kJ/mol。结果显示,相结构对铒氘化物的热稳定性具有显著影响。提出了基于实验热解吸谱和Redhead理论模型来评估升温速率影响金属氢化物热解吸特性的方法,采用该方法可大幅减少实验工作量。     

核电站温排水的热污染控制对策

核电站温排水的余热排放对生态环境造成的负面热影响（即热污染）已日益引起社会关注。文章基于国内现有的温排放控制标准可执行性不强以及电厂温排水余热的利用方式单一、利用效率不高的现状，提出我国现阶段核电站温排水的热污染控制需从温度标准制定（即温排水混合区若干关键控制参数的确定）和温排水余热的综合利用途径的开发这两方面入手，同时开展深入细致的研究。在对国外的主要余热利用途径和国内火电厂余热利用途径调研、分析的基础上，提出了结合生态工程原理进行温排水余热综合利用方案设计的建议。     

西安脉冲堆热柱孔道中子束流参数测量

采用飞行时间法测量了西安脉冲堆热柱孔道热中子束流中子能谱分布,能谱测量结果较Thermal Maxwellian理论谱偏软,中子谱平均能量为0.042±0.01eV.采用金箔活化法测得热柱孔道出口前端热中子注量率为1.18×105 cm-2·s-1,热中子注量率测量的不确定度为3%.     

Thermal deformation of fuel elements

The authors calculate the temperature drops in the walls of cassette-type fuel elements under neutron fluxes with radial gradients. The thermal deformations of the wails are measured in the working range of temperature drops.Translated from Atomnaya Énergiya, Vol. 21, No. 1, pp. 22–26, July, 1966.     

Thermal conductivity of neptunium dioxide

The thermal diffusivity of neptunium dioxide was measured in the temperature range from 473 to 1473 K by using a laser flash method. The thermal diffusivity slightly decreased with increasing temperature in the temperature range investigated. The heat capacity of NpO₂ was measured in the temperature range from 334 to 1071 K by using a drop calorimetry method. The heat capacity of NpO₂ determined in this study was slightly larger than that of UO₂ and about 7% smaller than that of PuO₂. The thermal conductivity of NpO₂ was determined from the thermal diffusivity, the heat capacity and the bulk density. It was found that the thermal conductivity of NpO₂ from 873 to 1473 K lay between those of UO₂ and PuO₂.     

热化截面库SabDEP制作与热化截面插值方法

加工生成了基于ENDF/B Ⅶ及其评价方法的新热化ACE(ACompactENDF)截面库SabDEP（工程物理系热化截面库）,包括轻水、重水、Be、石墨、H/Zr和Zr/H共6种材料,每种材料含6个温度点。对SabDEP库进行了微观截面比对验证和积分计算验证,重水的截面相对于原来生成的截面有很大改进。在清楚ACE文件结构基础上,对热化截面开展了温度插值方法研究,取得了很好的插值结果。     

Thermal neutron cross-sections of magnesium

Basic data necessary for the calculation of the thermal neutron scattering cross-section of magnesium were defined. The calculation scheme is the standard one used in reactor physics. For this purpose, the NJOY code is the main piece of software. Small modifications were needed in the NJOY's module LEAPR to take into account the specific lattice structure of magnesium. As a result we obtain a ENDF-6 standard conforming thermal data evaluation containing both coherent elastic scattering and incoherent inelastic scattering. The calculated values were checked against experimental values. Finally, a comparison of transmission coefficients through magnesium annular structure was done using the free gas and crystal models.     

Thermal shock in nuclear reactors

Most types of liquid cooled reactors undergo rapid changes in coolant temperature during abnormal operating conditions, which cause components adjacent to the coolant to undergo rapid surface temperature changes. The differential expansion between surface and bulk material caused by repeated thermal shocks can induce fatigue or cyclic creep damage. In thick walled components individual thermal shocks may cause rapid fracture from pre-existing defects. This paper reviews the reported experimental and analytical work defining the temperature, stress and resultant damage in reactor structural components subject to thermal shock.     

FCM燃料热学性能分析

研究了利用有限元分析软件ABAQUS对全陶瓷微封装燃料(FCM燃料)芯块进行热学性能分析的方法,并对FCM燃料芯块和传统UO_2芯块的热学性能进行了对比分析。研究结果表明:FCM芯块温度分布趋势与UO_2芯块相同,但具有较大不均匀性;典型压水堆运行工况下,FCM燃料芯块的燃料温度远小于UO_2芯块的温度;在相同线功率密度下,FCM芯块温度对燃耗变化不敏感;在相同燃耗下,FCM芯块随线功率密度增加温度升高的速率相比UO_2芯块更慢。     

Thermal Conductivity of Hafnium Hydride

We prepared fine bulk samples of Hf hydrides with various hydrogen contents, viz., the H/Hf ranges from 1.62 to 1.72. It was confirmed that all the Hf hydrides prepared in the present study exhibited a cubic delta phase with the fluorite-type structure. In the temperature range from room temperature to around 650 K, we measured the heat capacity and thermal diffusivity of the samples and evaluated the thermal conductivity. We succeeded in proposing empirical equations describing the lattice parameter, heat capacity, and thermal conductivity of Hf hydrides, as a function of temperature and hydrogen content.     

Thermal stresses in reactor constructions

Conditions for the appearance of thermal stresses in reactors are investigated; also their magnitude and the danger they create are estimated. The influence of the form of the heat-generating elements (HGE) on the temperature drop and magnitudes of thermal stresses is analyzed; recommendations are given with the aim of decreasing the harmful effect of thermal stresses.The methods from the theory of elasticity employed in the calculation of thermal stresses have significant limitations. In many cases when estimating the magnitude and degree of danger created by the thermal stresses, when combining such stresses with mechanical stresses, and also when seeking a way to decrease them, other effects such as fluidity, creep, initial breakdown, and microscopic processes must be taken into consideration.