氦-氙混合气体物性对布雷顿循环影响分析

将对应态原理用于Chapman-Enskog理论修正，得到的半经验公式可较好地预测二元惰性混合气体物性。采用Fortran 95开发了氦-氙混合气体物性计算程序，分析了氦-氙混合气体物性随摩尔质量、温度、压力的变化关系。在此基础上分析了物性变化对空间布雷顿循环的绝热系数、对流换热性能、阻力特性的影响。结果表明：压力为2.0 MPa、温度为400 K时，随着摩尔质量的增加，氦-氙混合气体的绝热系数由0.40（纯氦气）增加到0.44（纯氙气）；混合气体相对于纯氦气的相对对流换热系数随摩尔质量的增加呈先增大后减小的趋势，在15 g/mol附近取得极大值；相对压损系数则随摩尔质量的增加单调递增。分析结果可为氦-氙混合气体在空间核反应堆电源中的应用提供设计依据。     

氦氙混合气体冷却反应堆单通道程序开发

闭式布雷顿循环在大功率空间核电源方面具有广阔的应用前景。采用氦氙混合气体作循环工质可提高布雷顿循环的性能,且由于其良好的换热能力,可直接用作反应堆的冷却剂。在概念设计阶段,为适应频繁改动反应堆设计的需要,开发了氦氙混合气体冷却反应堆单通道分析程序。其中氦氙混合气体的物性参数采用理论方法预测。程序采用FORTRAN 90语言编写,并集成画图功能。程序可用于计算环形流道和圆管流道,通过对同一个算例的单通道计算结果与FLUENT计算结果或实验数据进行对比,初步验证了程序的正确性。     

基于RELAP5的氦氙流动换热计算模块开发与验证

反应堆热工系统分析程序是开展热工水力计算与安全评价的重要工具。为开发适用于氦氙气冷空间堆的热工系统分析程序,本文在RELAP5/MOD40程序中拓展了氦氙混合气体（He Xe）物性计算模块,添加了适用于He Xe的传热关系式,将拓展后程序计算值与实验值进行对比。结果表明：程序默认的Sutherlands定律用于He Xe物性计算时将引入较大误差;Dittus Bolter公式对He Xe对流换热时的Nu预测偏高,将导致不保守的壁温计算结果。拓展后的程序对He Xe压降和换热计算结果均与实验值吻合较好,验证了程序开发的正确性以及程序用于He Xe流动换热计算的功能。本研究可为系统层面程序开发奠定基础。     

基于气动悬浮的高温氧化物熔体热物性测量

堆芯熔融物的热物性是研究反应堆严重事故进程及堆内堆外现象机理的重要基础参数。当堆芯熔化时，堆内温度达3 000 K,形成U-Zr-O-Fe多元混合物，而气动悬浮技术是优选的高温下测量堆芯熔融物基础热物性的技术。本文描述了一套基于气动悬浮和激光加热技术的密度、表面张力和黏度的测量装置，目前已实现高温氧化物密度的实验测量。装置采用收缩-扩张型锥形喷嘴悬浮球状样品，采用CO₂连续激光器加热并熔化样品，采用双色红外测温仪监测样品的温度并进行激光器功率反馈控制；采用高速相机记录样品轮廓的变化，并结合图像分析法计算样品的体积，最后得到被测材料在高温下的密度。实验测量得到2 750～3 200 K范围内氧化锆熔体的密度，其在熔点(2 988 K)处的密度为4.717 g/cm~3,温度系数为-7.202×10^-4 g/(cm~3·K)。     

FKZr的热物性及热稳定性研究

熔盐堆冷却剂的热物性是熔盐堆物理、热工水力学设计以及安全分析的重要参数。KF-ZrF4(58-42 mol%)(FKZr)是熔盐堆中的一个具有潜在应用价值的冷却剂。该组成熔盐的热物性在文献中鲜有报道,这为其实际应用带来困难。分别采用差示扫描量热(Differential Scanning Calorimetry,DSC)、阿基米德和热重分析等方法测量和表征了FKZr熔盐的熔点、熔化焓、密度等重要的热物性参数和热稳定性。实验结果表明FKZr的熔点为693.6 K,与文献报道结果一致,符合熔盐堆中冷却剂的要求;熔化焓为71.8 J·g?1;密度为??3.3841?0.8954?10?3T(753?923 K);热重分析表明FKZr在873 K下性质稳定,不发生明显的挥发现象。     

钨中氘氦行为的高分辨热脱附谱实验方法研究

氢同位素在材料中的扩散、捕获和滞留等行为可通过热脱附谱实验方法进行研究。为实现对同时含有氘氦的钨材料进行热脱附测量并研究钨中氘氦滞留行为，搭建了1套基于高分辨四极质谱仪的热脱附实验系统HiTDS。HiTDS实现了1.2×10^-6 Pa的高本底真空度，速率为1 K/s的精确线性升温，最高加热温度达1423 K，能准确测量样品中气体元素的脱附速率和脱附量。通过配备高分辨四极质谱仪，HiTDS可快速分辨氘氦元素并测量其脱附速率。HiTDS经过调谐校准、标定系数标定后，对氘氦等离子体辐照钨样品进行了热脱附测量。测得的氘氦热脱附谱显示，纯氘脱附量与剂量正相关，而氦的引入显著抑制氘滞留并使其趋于饱和。热脱附实验结果与类似辐照条件的其他研究成果基本一致，检验了该实验方法的有效性。     

托卡马克弯晶谱仪双晶体结构应用的初步研究

X射线弯晶谱仪作为托卡马克装置等离子体温度和旋转速度等参数诊断测量的重要手段之一,通常利用单晶体衍射分光来测量某种特定杂质的特征谱,这也限制了弯晶谱仪所能测量的等离子体温度范围。为解决更高温度等离子体测量问题,有效提高目前弯晶谱仪诊断系统温度测量范围,用双晶体代替原有单晶体,通过选择合适的晶体和Bragg衍射角组合,利用同一个探测器同时测量类氢和类氦的氩离子光谱,实现更高更宽温度范围测量。本文就东方超环(Experimental Advanced Superconducting Tokamak,EAST)弯晶谱仪双晶体应用方面的设计和技术实现进行了阐述,并首次在EAST装置上成功实现了氩离子类氦和类氢谱线的测量,利用类氦线和类氢线拟合得到的氩离子温度非常接近,验证了双晶体结构的可行性。     

钯合金管气相色谱-质谱联合分析

本文介绍了使用氢载气钯合金管分离器作为色谱-质谱联用的过渡装置的试验情况。通过纯化器,杂质含量小于0.1ppm;分离器性能效率约为100%,浓缩系数为2.0×10~2。用本装置做了氦和甲烷混合气体的分析,并对工作温度、压差、残留氢量和连接管路的死体积等进行了讨论。     

熔融物热细粒化的实验研究

通过小规模细粒化实验(SSFT)实验装置开展锡、铅及锡铅合金为熔融物材料的热细粒化实验研究。研究材料物性、下落高度、熔融物初始温度及冷却水温度等对热细粒化的影响;通过分析实验碎片的形貌及大小分布,研究不同参数范围内熔融物热细粒化机理,给出了细粒化机理分区图谱。     

133Xe和131mXe混合气体刻度氙符合系统探测效率

作为全面禁止核试验条约(CTBT)国际监测系统(IMS)16个放射性核素实验室之一,北京放射性核素实验室对惰性气体氙-符合系统测量方法进行了研究,用于氙同位素(131mXe、133mXe、133Xe和135Xe)放射性活度测量。准确标定系统的探测效率是放射性氙活度准确测量的重点和难点。本文在剖析氙-符合系统测量原理的基础上,研究建立了采用未知活度的133Xe和131mXe混合气体进行-符合系统效率刻度的方法,对北京放射性核素实验室-符合系统测量符合能谱中部分感兴趣区的探测效率进行了刻度。     

Nusselt number correlation for turbulent heat transfer of helium-xenon gas mixtures

A gas-cooled nuclear reactor combined with a Brayton cycle shows promise as a technology for high-power space nuclear power systems.Generally,a helium-xenon gas mixture with a molecular weight of 14.5-40.0 g/mol is adopted as the working fluid to reduce the mass and volume of the turbomachinery.The Prandtl number for helium-xenon mixtures with this recommended mixing ratio may be as low as 0.2.As the convective heat transfer is closely related to the Prandtl number,different heat transfer correlations are often needed for fluids with various Prandtl numbers.Previous studies have established heat transfer correlations for fluids with medium-high Prandtl numbers(such as air and water)and extremely low-Prandtl fluids(such as liquid metals);however,these cor-relations cannot be directly recommended for such helium-xenon mixtures without verification.This study initially assessed the applicability of existing Nusselt number cor-relations,finding that the selected correlations are unsuit-able for helium-xenon mixtures.To establish a more general heat transfer correlation,a theoretical derivation was conducted using the turbulent boundary layer theory.Numerical simulations of turbulent heat transfer for helium-xenon mixtures were carried out using Ansys Fluent.Based on simulated results,the parameters in the derived heat transfer correlation are determined.It is found that calculations using the new correlation were in good agreement with the experimental data,verifying its appli-cability to the turbulent heat transfer for helium-xenon mixtures.The effect of variable gas properties on turbulent heat transfer was also analyzed,and a modified heat transfer correlation with the temperature ratio was estab-lished.Based on the working conditions adopted in this study,the numerical error of the property-variable heat transfer correlation was almost within 10％.     

Effective thermal conductivity of MOX raw powder

The radial temperature distribution of plutonium and uranium mixed oxide powder loaded into a cylindrical vessel was measured in air and argon gas, and the effective thermal conductivity was calculated from the measured temperature distribution and the decay heat. The effective thermal conductivities were small values of 0.061-0.13 W m^-1 K^-1 at about 318 K, and changed significantly with O/M, bulk density and atmospheric gas. The results in this work were analyzed by the model of Hamilton and Crosser and a new model for the effective thermal conductivity of the powder was derived as functions of powder properties and thermal conductivity of atmospheric gas.     

基于CFD方法的PCHE窄小流道内超临界CO2流动传热特性数值研究

采用计算流体动力学（CFD）方法对Z字形通道的印刷电路板式换热器（PCHE）的热工水力特性进行了研究，结合物性拟合公式和用户自定义函数（UDF）计算超临界CO₂物性；湍流模型采用SST k-ω模型，通过摩擦阻力系数和传热系数的实验数据对方法进行了验证。模拟结果表明，流体在弯折点处，加速核心区域向外侧壁靠近；在弯折点下游，存在较大压降，且随分离流的减弱而减小。      

Fuel swelling due to retained fission gas and thermal effects during high temperature transients

Fuel swelling of previously irradiated pressurized-water-reactor-type fuel rods tested under power-cooling-mismatch conditions is due to retained fission gas and thermal effects within the film boiling region. In this paper empirical correlations for fuel swelling are presented, and mechanisms contributing to the observed swelling and the applicability of an analytical fission gas behavior computer code (GRASS-SST) to fuel swelling are evaluated. Major contributors to fuel swelling are fuel melting and expansion, expansion of solid fuel, fission gas bubble coalescence, fission gas diffusion to grain boundaries, and change in surface tension of fuel upon melting. The contributions to fuel swelling of solid fission products and the effects of cladding contraction and wall thinning on rod swelling are also included. The overall empirically-calculated fuel swelling values and the GRASS-SST code calculated values are compared with measured values. The agreement between measured and empirically calculated fuel swelling is generally close. Fuel swelling due to retained fission gas during the film boiling transient, as calculated by the GRASS-SST code, was found to be in good agreement with experimental results.     

Thermophysical properties of americium-containing barium plutonate

Polycrystalline specimens of americium-containing barium plutonate have been prepared by mixing the appropriate amounts of (Pu_0.91Am_0.09)O₂ and BaCO₃ powders followed by reacting and sintering at 1600 K under the flowing gas atmosphere of dry-air. The sintered specimens had a single phase of orthorhombic perovskite structure and were crack-free. Elastic moduli were determined from longitudinal and shear sound velocities. Debye temperature was also determined from sound velocities and lattice parameter measurements. Thermal conductivity was calculated from measured density at room temperature, literature values of heat capacity and thermal diffusivity measured by laser flash method in vacuum. Thermal conductivity of americium-containing barium plutonate was roughly independent of temperature and registered almost the same magnitude as that of BaPuO₃ and BaUO₃.     

Thermal conductivity of BaPuO3 at temperatures from 300 to 1500 K

Polycrystalline specimens of barium plutonate, BaPuO₃, have been prepared by mixing the appropriate amounts of PuO₂ and BaCO₃ followed by reacting and sintering at 1600 K under the flowing gas atmosphere of dry-air. The sintered specimens had a single phase of orthorhombic perovskite structure and were crack-free. The Debye temperature of BaPuO₃ was determined from the sound velocity and lattice parameter measurements. The elastic moduli were also determined from the longitudinal and shear sound velocity. The thermal conductivity of BaPuO₃ was calculated from the measured density at room temperature, literature values of heat capacity, and thermal diffusivity measured by a laser flash method in vacuum. The thermal conductivity of BaPuO₃ was roughly independent of the temperature and was almost the same magnitude as that of BaUO₃. This was markedly lower than the conductivities of other perovskite type oxides and was about one-tenth that of UO₂ around room temperature. The temperature dependence of the thermal conductivity of BaPuO₃ was found to be quite similar to that of BaUO₃.     

高温氦氙气体微通道回热器的传热流动特性分析

以氦氙气体作为工质的闭式布雷顿循环系统是大功率空间热电转换目前最可行的技术方案。高温氦氙气体回热器是闭式布雷顿循环系统的关键部件，其性能明显影响系统发电效率、系统发射质量以及系统布置的紧凑性。本文采用计算流体力学和传统理论分析方法，针对高温氦氙气体微通道的结构及成型工艺选择、工作温度与回热器回热度的关系、流量与性能参数的关系等进行了研究。研究结果表明，采用精雕工艺作为微通道的成型工艺可在不降低回热器换热性能的前提下降低压降40%，减少质量17%。在设计参数条件下，微通道之间设置联通通道不会增加换热能力。回热器回热度随流量的增加而减小，且存在拐点，对于拟研制回热器的设计参数，设计流量应不高于0.24 g/s。回热器结构合理性用单位压降和温降条件下换热面积与功率的比值来判断，降低雷诺数能有效提高回热器的结构合理性。     

Measurement of specific energy losses of individual fission fragments with a back-to-back δE−E detector system

The specific ionization of fission fragments of specified charge and $\text{E}\text{M}$ values in thermal neutron induced fission of ²³⁵U have been measured employing a back-to-back gridded ionization chamber ΔE-semiconductor detector E setup. The measurements were carried out for the case of a mixture of argon (95%) and methane (5%) gases at two gas pressures, 44 Torr and 270 Torr. The experimental data for the lower gas pressure were used to determine the effective charge parameter γ for the fragments at various velocities. These γ-values have been used to compute the fragment energy losses at the higher gas pressure and are compared with the measured energy loss values.     

高放废物玻璃固化体工艺模型及组分影响研究

用极顶设计不确立最优化７组分玻璃固化体试验方案对方案对１０２个试验配方进行高温粘度和电导电阻率工艺性能测试，并对其中经过高速的８６个配方建立精度高阶重心多项式工艺性能预测模型。