垂直圆管内超临界R134a对流传热实验研究

为研究超临界压力下的对流传热特性,对超临界压力氟利昂R134a在内径25 mm垂直圆管中的受热上升流动传热进行了实验研究,获得压力4.5 MPa和4.7 MPa、质量流速G=400~700 kg/(m2·s)、热流密度q=30~60 k W/m2的实验数据,对换热强化和传热恶化的规律和特性以及其影响因素进行了分析。结果发现,在拟临界区附近,超临界压力R134a出现明显的强化换热现象。在低质量流速或高热流密度下发生传热恶化,其恶化边界为q/G0.06 k J/kg。在特定的工况下观察到两次传热恶化:第一次发生在临近入口区域,在不同流体入口温度下均观测到恶化;第二次发生在远离入口区域,仅在一定流体焓值范围内存在。实验参数敏感性分析表明,传热强化随质量流速的增加、热流密度的减小、压力的降低而增加,而传热恶化则相反。     

竖直圆管内超临界二氧化碳强迫对流传热实验研究

为分析超临界二氧化碳强迫对流传热特性,开展竖直圆管内超临界二氧化碳强迫对流传热特性实验研究。实验结果表明:实验参数范围内存在明显的浮升力效应和流动加速效应;对于向上流动工况,随浮升力效应增强超临界二氧化碳从强迫对流传热过渡至混合对流传热,最后发展为自然对流传热,传热能力有弱化到逐渐恢复直至强化;对于向上流和向下流动工况,流动加速效应皆弱化传热。基于实验数据建立新的超临界流体传热关联式,在实验工况范围内95.03%的预测值与实验值偏差为±30%以内。     

超临界流体中的传热：传热机理分类

因为较小的温度变化就能引起物理性质的明显改变，没有现存的工程关系式和模型能精确地预测超临界流体中的传热。本文力求将现存关系式适用的工况进行分类并更好地理解这些局部传热机理。第一个目标是本文关注的焦点。FLUENT被用来计算各种热流密度和质量流速工况下的壁面温度，其结果用来与实验数据相比较。因为模型是为宽范围流动工况而设计的，所以，应进行某些假设。模拟表明，在高质量流速工况下吻合较好，这时浮力效应可以被忽略。但是，FLUENT在预测高热流密度和低质量流速混合工况中见到的局部低传热速率时遇到困难。一个新的依赖于热流密度和质量流速通用参数被发展来区分在何种工况下这个FLUENT标准模型是适用的，这个全局Fmude数能被用作预测在何种工况下浮力效应占主导地位和更低的传热速率会发生的参数。     

双D形流道内超临界二氧化碳传热特性数值研究

对简单双D形流道内超临界二氧化碳传热特性进行数值研究。重点研究了热流体质量流速对换热功率和换热效能的影响,以及热流道失流工况对传热特性的影响。研究表明:随着热流体质量流速增加,换热器换热功率增加,换热器换热效能降低;换热器的换热能力受冷热流体温差驱动,热流体失流时换热器换热能力下降,壁面温度降低,与定热流密度传热存在一定差异。     

竖直圆管内超临界压力氟利昂传热试验研究

深入研究超临界压力下流体特殊的对流传热特性,对超临界水冷反应堆的堆芯设计至关重要。在上海交通大学SMOTH氟利昂回路上开展了压力4.3~4.7 MPa、质量流速600~2 500kg/(m2·s)、热流密度20~180kW/m2参数下的圆管内超临界上升流传热试验。远离拟临界温度区间内换热系数和Dittus-Boelter公式计算值很接近,热流密度越大,近拟临界区换热系数越小,小质量流速大热流密度下,发生显著传热恶化。加速效应无量纲数和浮升力无量纲数对传热特性显示了强烈的相关性。提出了氟利昂工质传热试验的传热恶化起始点关系式。Bishop关系式计算换热系数和试验值之间标准差很小,但整体略偏大;Jackson关系式计算值和试验值之间平均偏差很小,但标准差偏大。     

超临界水冷堆类四边形子通道亚临界水的传热试验研究

在压力为11~19 MPa,质量流速为700~1300 kg/(m2·s),热流密度为200~600 k W/m2的工况范围内,对超临界水冷堆(SCWR)堆芯棒直径为8 mm,栅距比为1.2的类四边形子通道的传热特性进行试验研究。结果表明:热流密度对类四边形子通道管管内的传热特性的影响显著,热流密度越高,传热恶化越容易发生;在较低的质量流速下,传热恶化发生可能性较大,质量流速较高时,对传热特性影响较小;压力对类四边形管管内传热特性的影响明显,压力越高,传热恶化现象越易发生,且临界干度值越低,传热恶化所覆盖的焓值区域越大。     

垂直管内超临界水传热实验研究

在宽广的实验范围内对直径10 mm垂直管内超临界水在不同工况下的传热特性进行了实验研究,分析了热流密度、质量流速及压力变化对内壁面温度及传热系数的影响规律。实验参数为：压力23、25、26 MPa,质量流速450~1 200 kg/（m²•s）,热流密度200~1 200 kW/m²。实验结果表明：随主流温度的升高,壁面温度逐渐上升,在拟临界点附近由于物性剧变存在传热强化现象;热流密度的增加以及质量流速的减小均会削弱传热强化现象,并导致传热恶化;压力的影响主要体现在传热恶化、强化的起始热流密度和起始主流温度的不同。     

竖直圆管内超临界流体混合对流传热特性理论分析

理论推导了变密度引起的浮升力效应和流动加速效应对超临界流体混合对流传热特性的影响。结果表明,浮升力效应和流动加速效应通过改变壁面边界层外缘的切应力影响湍流对传热传质的贡献,进而改变超临界流体混合对流传热特性。浮升力效应通常在加热区域入口及上游区域表现明显,而流动加速效应在主流区流体温度达到拟临界温度时更显著。与实验研究结果对比发现,新建立的浮升力因子和流动加速因子可较好地预测竖直圆管内超临界流体混合对流条件下拟临界区域的局部传热特性。     

简单通道内超临界水传热特性实验研究

针对各国超临界水冷堆燃料组件设计方案,选取圆管、圆环形通道、方环形通道3种具有热工水力代表性的简单通道,开展超临界条件下水工质的传热特性实验研究。实验结果表明,热流密度、质量流速和压力3种热工参数对不同简单通道传热特性的影响趋势基本一致;在相同质量流速和压力下,换热系数在靠近拟临界温度处存在峰值,且随热流密度的增大而减小;在相同热流密度和压力下,相同主流体焓处对应的换热系数随着质量流速增加而增加;压力对超临界水传热特性影响较弱,仅在拟临界区域内换热系数峰值稍有不同;实验中出现了拟临界区域的传热恶化现象,传热恶化发生时壁温出现局部峰值。     

格架对低流量对流传热影响的数值研究

针对带格架圆管在低流量高热流密度下的热工水力特性开展了数值研究。通过经验关联式与实验数据分别对光滑圆管内单相水低流量对流传热与格架效应进行标定,确立了基于SST k-ω模型的计算流体动力学（CFD）方法。模拟结果表明,格架下游传热特性取决于浮升力参数大小。强迫对流区与混合对流传热下降区,格架下游传热始终增强,努塞尔数呈指数衰减;混合对流传热恢复区与自然对流区,由于流场与传热的耦合作用,格架下游传热存在恶化现象,努塞尔数呈阻尼振荡。格架下游传热影响范围随着浮升力参数的增加先增大后减小。格架阻塞比越大,传热振荡越剧烈,格架致传热恶化的程度提高。该研究可为低流量堆芯内格架设计提供参考。      

Increase in internal friction in uranium with change in temperature

On the basis of the previously described increase in internal friction in uranium during heating, a semiquantitative evaluation was made of the dependence of increase in internal friction on the rate of heating, frequency and amplitude of vibrations. The results of the calculations agree satisfactorily with data obtained experimentally. A study was made of the effect of the initial state of the specimen on the increase in internal friction at the initial stages of heating.     

广东省进出口食品中的放射性检验

报道了广东省商检中心放射性检验室开展的广东进出口食品中的放射性检验工作。介绍了检验工作采用仪器的主要性能及应用;给出了分析测量方法和探测下限以及实验的质量保证措施,并给出了检验室测量的广东省几种食品中的放射性含量范围,测量结果与我国食品中放射性活度变化范围大体一致。     

Tritium concentrations in precipitation in Shanghai

Tritium concentrations in precipitation can be used as a criterion to evaluate the tritium baseline of the environment. The tritium concentration in precipitation in Shanghai during 2014-2015 was determined. Values ranged from 0.68 ± 0.04 to 4.11 ± 0.39 Bq/L, and it showed a decreasing trend compared with historical data; however,the values were slightly higher than the natural background tritium level. Additionally, the tritium concentration shows a seasonal variation: It was higher in autumn and winter and lower in summer and spring. A comparison of concentrations in precipitation in Shanghai and around the Qinshan Nuclear Power Plant reveals no correlation,implying that the nuclear power plant operations may not affect the environment of Shanghai. Thus, the raised tritium concentrations in Shanghai might be due to the effects of monsoons, spring leak, raindrop, or other activities that generate tritium there. Those activities may include chemistry research that uses tritium as a tracer.     

微机在核物理实验应用中的抗干扰问题

本文简单介绍了计算机在核物理技术应用中的各种噪声，并初步探讨了抑制噪声的方法。     

Tritium concentrations in precipitation in Shanghai

Beamline BL17 U1 at Shanghai Synchrotron Radiation Facility is an energy-tunable macromolecular crystallography beamline that has been in user operation since 2009. Growing demand from the user community for a small beam and related experimental methods have motivated upgrades of the devices in the endstation.Minibeam modes have already been developed for operation. A self-integrated diffractometer reduces the sphere of confusion of the rotatory axis to 1μm. The new diffractometer is equipped with an upgraded on-axis viewing system that can improve the resolving power. Additionally,the area detector was also upgraded to the newest generation of detectors, the EIGER X 16 M, which can collect data at 133 Hz. After these upgrades, the endstation became virtually new. This paper covers the upgrade of the endstation devices and gives the first data collection results.     

2010年的美国铀矿业

2010年,美国铀矿总共施工7 209个钻孔,总进尺1 493 520 m;生产铀1 628.55t;铀矿业总支出费用为2.773亿美元,其中铀矿地勘费支出为3 450万美元,占铀矿业总费用的12.44％.铀矿地勘钻探费用为4 460万美元,占铀矿业总费用的16.08％.     

我国东南沿海城市地下建筑氡浓度分布

为了解东南沿海城市地下建筑氡浓度的分布，用固体核径迹法(SSNTD’s)，分别在春、夏、冬3季对沿海7城市地下建筑室内氡浓度进行调查。结果表明，福州具有最高的平均氡浓度，上海的平均氡浓度最低。季节的变化对地下建筑室内氡浓度有影响，各城市氡浓度平均值夏季最高、冬季最低。各城市夏季氡浓度与该城市的年均值的比值与城市中各测点氡浓度之间的离散度有一定的相关性。夏季地下建筑室内氡浓度高的城市，它的平均氡浓度受某些具有高氡水平测点的影响大。     

Plutonium use in nuclear power in Russia

Conclusions The following concept of plutonium utilization based on the evolutionary development of the traditional technology in our country arises: The main problem of any short-term program of dealing with plutonium must be solved — reliable and safe storage of separated energy plutonium and freed weapons plutonium before utilization in reactors. Plutonium (mainly energy plutonium) is utilized primarily in BN-800 fast reactors and the development of technology using weapons plutonium in BN-600 reactors starts. In the future attention should be focused on nuclear-power centers patterned after the Industrial Association “Mayak” (RT-1 plant, Complex 300, BN-800) with reliable nonproliferation of weapons plutonium. It is extremely important to speed up work on the completion of Complex 300: This work must be completed before BN-800 is ready. In the future efforts must be concentrated on the following: development and implementation, in BN-800, of an economically more efficient plutonium-burning core; the possibility of building light-water reactors with the required degree of safety for effective plutonium utilization must be justified (including a “cold” core based on cermet fuel); and, development and implementation of technology for a safe and an ecologically acceptable closed nuclear fuel cycle based on plutonium and²³³U with burnout of Am, Np, and Cm. Ministry of Atomic Energy of the Russian Federation. Institute of Physics and Power Engineering. A. A. Bochvar All-Union Scientific-Research Institute of Standardization in Machine Building. Special Design Office for Machines. Translated from Atomnaya énergiya, Vol. 76, No. 4, pp. 326–332, April, 1994.