带格架棒束通道交混湍流数值模拟研究

采用雷诺时均模拟(RANS)和大涡模拟(LES)对MATi S-H实验进行模拟计算,得到格架交混后棒束通道内冷态单相湍流流场,通过比较格架下游特定位置处速度分量分布,发现采用精细网格的LES能够较为准确地计算湍流流场平均速度以及脉动速度的分布,与实验结果符合较好。LES结果表明,棒束通道内格架交混湍流流场具有明显的波动,脉动峰值离散分布;子通道内瞬时时刻的涡旋因子SM沿轴向也并非单调衰减,而是具有相对持续的脉动特征,最大脉动值大约是SM最大值的5%;LES的瞬时速度场计算结果可以为进一步的力学分析提供参考。     

燃料组件典型栅元湍流激振数值研究

为掌握全长范围内的燃料棒振动响应特性,以用于燃料棒微动磨损寿命分析,本研究运用计算流体动力学（CFD）方法,对燃料组件典型栅元的湍流激振进行数值模拟分析,并通过棒表面的瞬态脉动压力分布开展不同夹持力下的单棒瞬态动力学分析。研究表明:格架上游的截面平均湍动能约为0.1 m2/s2,格架临近出口位置湍动能达到峰值的0.65 m2/s2,格架的存在显著增强了流场的湍流强度,这是造成燃料棒湍流激振的主要原因;通过瞬态动力学分析确定了均方根振幅最大的定位格架位置,并建立了该格架的均方根振幅和振动速度随夹持力变化的关联式。本研究将为后续微动磨损理论计算及实验验证奠定基础。      

用于同轴喷射流引起的温度振荡数值模拟的湍流模型有效性研究

本文采用Fluent软件对同轴喷射流冷热流体搅混引起的三维温度振荡现象进行数值模拟。模拟中，分别选取几种代表性的湍流模型，如大涡模拟(LES)、雷诺应力模型(RSM)及标准k-ε模型。并将模拟结果与实验结果进行了对比，发现：LES是最适合预测冷热流体搅混特性的模型；LES可准确预测温度振荡在半径、高度和方位角方向的平均温度，而雷诺平均法(RANS)的结果则延长了流体的混合过程；LES可预测流体的瞬态温度振荡，RANS则无法预测。     

脉动流下定位格架下游时均流场分布特性研究

研究流量波动下棒束通道内定位格架下游瞬时流场演变特性对于揭示海洋条件下燃料组件内流动换热机理具有重要意义。本文应用粒子图像测速（PIV）技术获得了脉动流下棒束通道内定位格架下游时空演变流场结构,分析了脉动参数（脉动周期和脉动振幅）对定位格架下游速度分布和湍流特性的影响。结果表明,脉动流下定位格架下游时均速度与定常流动下时均速度差异较小,且基本不随脉动振幅和脉动周期变化而变化;脉动流下的定位格架下游横向速度和轴向速度均方根与定常流动下的速度均方根存在明显差异,且随脉动参数变化呈现出不同的变化趋势。本文研究结果有助于揭示燃料组件在非稳态条件下瞬态特性,并为燃料组件的设计和优化奠定基础。      

竖直圆管内气泡运动的大涡模拟研究

基于两流体模型框架,使用雷诺平均N-S方程(RANS)和大涡模拟(LES)两种湍流模型对竖直圆管内的绝热离散气 液两相流动进行数值模拟研究。计算结果表明,采用恰当的相间相互作用模型,两种模型的时均模拟结果同实验均符合较好。气泡的壁面聚集现象被准确预测,速度场预测也较为准确。与基于RANS的SST湍流模型相比,采用WALE亚网格应力的大涡模拟得到的结果同实验符合得更好,且大涡模拟可给出流动的瞬态细节。     

CFD方法在棒束定位格架热工水力分析中的应用研究

利用UG、CFX程序和计算流体力学(CFD)方法对AFA-2G组件5×5棒束定位格架进行了几何建模和通道内单相水三维流场数值模拟,包括特定流速下流场的定性和定量分析、不同流速下的阻力特性分析等.将分析结果与相应试验结果进行了比较,结果表明:采用合理的结构简化、恰当的物理模型和数值求解算法,CFX程序能较好地模拟棒束定位格架通道内的单相水三维流场,其模拟结果与试验结果符合较好.     

离心式上充泵小流量工况转换瞬态流动特性

为研究核电站离心式上充泵由上充工况向小流量工况转换运行过程中的瞬态流动特性,基于RANS方程和RNG k-ε湍流模型,采用商业软件CFX对其进行定常数值模拟,并通过试验验证了数值计算方法的正确性。在此基础上,继续对该瞬态过程进行数值计算,得到上充泵内部流动瞬态压力及速度的变化规律。结果表明：在由上充工况向小流量工况转变过渡过程中,叶轮、导叶、出口涡壳的流道内压力有不同程度的上升趋势;在瞬态转变过程中,随着流量的减小,上充泵内部漩涡范围增大,流动形式也愈来愈差,导致压力和速度波动幅值增大;由于动静干涉影响,叶轮与导叶交界面附近监测点的压力和速度波动程度高于其他监测点的波动程度,双蜗壳流道内圈的波动高于外圈的波动。     

压水堆上腔室冷却剂温度振荡现象研究

为了解压水堆上腔室冷却剂的温度振荡现象,利用专业计算软件CFX,采用大涡模拟（LES）方法,对简化上腔室内的瞬态流场进行数值模拟,并与实际数据进行对比分析。结果表明,LES模型可较好地模拟上腔室的温度振荡现象;上腔室出口区域的温度波动多集中于低频部分,未呈现出明显的周期性;出口位置对流场温度分布有明显影响,自入口至上腔室出口中心线所在平面,外围及中心部分温度波动幅度较大,其余区域温度变化幅度较小;而自上腔室出口中心线所在平面至顶部区域,温度波动逐渐趋缓。     

URANS与LES对带分裂式交混叶片定位格架5×5棒束通道流场数值模拟研究

利用非定常雷诺平均纳维斯托克斯模拟（URANS）和大涡模拟（LES）对带分裂式交混叶片定位格架5×5棒束通道流动特性进行了研究。数值计算中建模考虑了格架条带、交混叶片等几何结构对流场的影响，并将模拟结果与MATiS-H基准实验进行了对比。结果表明，URANS与LES均能较好地模拟格架下游3个流速分量时均值；对于格架下游流速分量脉动值，URANS中非定常SST k?–?ω模型几乎不能够模拟出流速脉动值，非定常RSM模型对于流速脉动值模拟比实验值偏低。与URANS相比，LES能相对较为准确地模拟流速脉动值，然而LES对格架附近流速脉动值模拟结果与MATiS-H基准实验相比仍然偏低。      

棒束通道内定位格架搅混特性PIV可视化研究

定位格架作为燃料组件中重要的组成部件之一，不仅在结构上固定燃料棒，而且在燃料组件内热工水力性能同样显著，特别是对工质的搅混性能直接关系到反应堆的经济性和安全性，因此有必要对燃料组件内定位格架搅混特性进行研究。本文通过粒子图像测速（PIV）技术开展了棒束通道内定位格架上下游流场的可视化研究，对比了有无格架棒束通道内流场的分布特征，定量分析了定位格架对棒束通道流场搅混的贡献。对不同流速下定位格架下游横纵速度的沿程变化特性进行研究，发现了不同流速作用下定位格架对横向、轴向速度的促进和抑制规律。另外，通过速度均方根对下游的湍流特性进行了评估。实验结果可为数值计算提供全场的数据验证，并可为定位格架设计和优化提供基础。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

Interaction between uranium and humic acid (Ⅰ): Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) ＞SHA (HA from the surface) ＞THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g)ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5 - 6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

Information for authors

<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumen-     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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