低压下倾斜加热面临界热流密度模型研究

通过压力容器外部冷却实现熔融物堆内滞留已经成为先进非能动压水堆核电厂的一项重要的严重事故管理措施。这种措施能够成功的关键是压力容器下封头局部热流密度小于对应位置的临界热流密度(CHF)值。本文在气泡壅塞模型的基础上,开发出适合于低压下倾斜加热面的CHF机理模型。在模型的开发中,重点考虑了加热面倾角对气泡运动速度以及气泡层厚度的影响,同时修正了含气率的计算方法。模型预测值与实验测量值的误差在10%以内,说明本文的模型能较好的预测实验条件下的CHF值。     

内螺纹管临界热流密度预测与数值计算

基于壁面汽泡壅塞理论，针对近临界压力区两相流动沸腾的偏离泡核沸腾(DNB)现象，对垂直上升内螺纹管的DNB型临界热流密度(CHF)进行了数值计算研究。以内螺纹管为分析对象改进已有的汽泡壅塞模型，计算了汽泡层区与主流区的极限传递质量流量、湍流速度分布、汽泡层区临界截面含气率等本构关系，汽泡脱离直径的计算考虑了汽泡接触角的影响。本文模型还根据大量CHF实验数据拟合得到了新的α_b关联式。最后，基于Fortran语言编制了CHF的理论预测数值模型程序，研究分析了压力、质量流速、热平衡干度及进口欠焓对CHF的影响，并根据CHF查表值对本文模型进行评估，同时将实验得到的内螺纹管CHF数据与采用Bowring模型、Katto模型、Shah模型和本文模型计算的CHF进行比较，发现本文模型的误差最小，与实验值吻合结果较好，说明本文模型能较好地对垂直上升内螺纹管DNB型CHF进行预测。     

基于CMFD模拟的圆管内DNB型CHF预测

偏离泡核沸腾(DNB)型临界热流密度(CHF)的预测是压水反应堆热工水力分析的一项重要内容。本文使用商用CFD软件STAR-CCM+,采用欧拉两流体模型,模拟了16 MPa下在不同出口平衡含气率、不同进口流速下圆管内水的核态沸腾,并基于Weisman-Pei气泡雍塞模型预测CHF值。通过与查询表值进行比较,发现过冷工况下,本文采用的模型组合得到的CHF预测值与查表值差别在10%之内,两者吻合良好;但是在饱和工况下,计算值较查表值偏差比较大。针对饱和条件下的偏离泡核沸腾预测,本文的模型仍有待改进。     

基于喷嘴临界流实验对现有物理模型的评价

以水为工质、直径1.41mm的喷嘴为实验段，在稳态条件下进行临界流实验，覆盖的参数范围为：进口压力，0.4～22MPa；进口温度，40～371℃；进口含汽率，－3.5～0.98。结果分析表明：在欠热度高于一定值下流动未达到临界条件；在低欠热度和低含汽率区域两相间存在热力不平衡性，在较低压力下，它对临界流率的影响十分显著。将实验数据与均匀平衡模型、Moody模型、Henry-Fauske模型、Burnell模型以及Bernoulli公式的计算结果进行比较，显示了各模型在不同条件下的适应性。     

裂变气体气泡尺寸对弥散燃料颗粒内部特征的影响规律

在前期均匀裂变气体气泡尺寸弥散燃料颗粒开裂模型基础上,基于不同尺寸气泡压力作用于燃料相的米塞斯(Mises)应力相等这一假设条件,建立了非均匀气泡尺寸的燃料颗粒开裂模型,并通过模型计算了裂变气体气泡尺寸对燃料相等效层厚度、气泡中气体原子数、气泡压力、燃料相最大张应力等内部特征的影响规律。计算结果表明:当气泡半径较大时,燃料相等效层厚度与气泡半径近似呈线性关系,当气泡尺寸较小时,等效层厚度与气泡半径之比随气泡半径减小急剧增加;随着气泡半径减小,气体原子数浓度增加;在升温过程中气泡内壁最大张应力的增大速率明显高于开裂阻力,气泡半径越小,燃料颗粒开裂温度越低。     

核主泵叶轮叶片进口边位置对气液两相流动特性的影响

为了研究叶轮叶片进口边位置对核主泵气-液两相流动特性的影响,设计3种不同进口边方案,并对不同方案下的气-液两相流动特性进行定常、非定常模拟。通过对结果的分析,发现核主泵叶片进口边适当前伸,在发生失水事故时有助于保持一回路压力边界的稳定性,但前伸也会加剧叶片扭曲程度,使叶片吸力面气泡大量堆积;叶片进口边向后偏移,易在叶轮出口处产生较强的射流尾迹,引起较大幅度的压力脉动。经过比较分析,确定方案B为最优方案。在模拟基础上,对试验样机进行不同进口含气率工况下的外特性性能测试,测试结果表明:在进口含气率为0%的工况下,模拟数据与试验数据吻合性较好,泵性能达到设计要求;随着含气率的增加,试验值与模拟值出现较大的偏差,主要由于试验条件所限及模拟结果与试验结果的误差所导致。     

过冷水中单个蒸汽气泡凝结动力学过程研究

对高过冷度条件下单个蒸汽气泡的凝结过程进行了可视化研究,并与现有的计算模型进行了对比。实验结果表明:高过冷度条件下,运动速度较高的气泡脱离后,其底部产生的液体射流现象会加剧气泡的变形和凝结过程;而现有的计算关联式均无法较好地预测该条件下的气泡动力学行为,凝结末期的相对误差超过50%。此外,通过Sobol方法对气泡凝结模型进行了敏感性分析,并定量评估了不同实验范围内Reynolds数、Jacob数以及Prandtl数对气泡凝结的影响程度。     

过冷水中单个蒸汽气泡凝结动力学过程研究

对高过冷度条件下单个蒸汽气泡的凝结过程进行了可视化研究，并与现有的计算模型进行了对比。实验结果表明：高过冷度条件下，运动速度较高的气泡脱离后，其底部产生的液体射流现象会加剧气泡的变形和凝结过程；而现有的计算关联式均无法较好地预测该条件下的气泡动力学行为，凝结末期的相对误差超过50%。此外，通过Sobol方法对气泡凝结模型进行了敏感性分析，并定量评估了不同实验范围内Reynolds数、Jacob数以及Prandtl数对气泡凝结的影响程度。     

矩形通道临界热流密度计算模型的实验评价

自然循环条件下,矩形通道内的临界热流密度(CHF)发生受到很多因素影响,目前对其特征的把握尚不完善。将本研究中得到的实验结果与Katto的强迫循环和Zhang的自然循环两种CHF模型的计算值进行比较,分析两种模型在实验条件下的适用性以及入口流速、出口质量含汽率和压力对CHF的影响。研究表明:Katto模型的计算结果普遍高于实验值,而Zhang模型的计算结果与实验值符合较好。随着入口流速的增大,自然循环和强迫循环CHF均逐渐增大;随着出口质量含汽率的增大,两类循环的CHF均减小;随着压力的增大,两类循环的CHF都增大,而在较大压力条件下自然循环CHF的增长速率随系统压力的增大而减小。     

矩形通道临界热流密度计算模型的实验评价

自然循环条件下,矩形通道内的临界热流密度(CHF)发生受到很多因素影响,目前对其特征的把握尚不完善。将本研究中得到的实验结果与Katto的强迫循环和Zhang的自然循环两种CHF模型的计算值进行比较,分析两种模型在实验条件下的适用性以及入口流速、出口质量含汽率和压力对CHF的影响。研究表明:Katto模型的计算结果普遍高于实验值,而Zhang模型的计算结果与实验值符合较好。随着入口流速的增大,自然循环和强迫循环CHF均逐渐增大;随着出口质量含汽率的增大,两类循环的CHF均减小;随着压力的增大,两类循环的CHF都增大,而在较大压力条件下自然循环CHF的增长速率随系统压力的增大而减小。     

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.     

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.     

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。     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.