异种材料典型螺纹联接件在预紧和热循环条件下的力学行为

在核电厂堆内构件中,如果螺纹联接结构的联接件和基体采用两种不同的材料,由于螺纹联接件材料的热膨胀系数小于基体材料,在升温过程中将产生较大的附加应力.本文以典型螺纹联接件M12为例,模拟堆内热循环载荷条件,对其进行有限元仿真计算分析.在与试验结果及理论分析、经验公式互相比较的基础上,对预紧力矩、螺纹联接件和基体的变形量、联接件在预紧力、升温、降温等不同载荷条件下的应力等参量变化情况进行了研究,为工程设计提供了可靠的依据.     

堆内构件螺纹联接件应力分析与评定

堆内构件中的螺纹联接件数量众多且受力复杂,为确保堆内构件结构的完整性,螺纹联接件的应力和疲劳分析必须满足ASME规范的相关要求.鉴于堆内构件对核电厂安全运行的重要性以及在核电厂运行工况下受到多种静、动态外力的作用,本工作根据规范要求,对堆内构件螺纹联接件的预紧力、受力状态、变形计算、载荷分类和组合、应力分析与评定等进行了综合研究,并根据研究成果开发了堆内构件联接件应力评定专用程序,使堆内构件联接件的应力评定工作能更准确、有效地进行,为工程设计和应用提供了可靠和便捷的工具.     

非岩性地基条件下核岛厂房-桩-土非线性动力相互作用特性研究

在模拟水环境下,对堆内构件压紧弹簧的缩比试样进行了刚度试验,并与有限元模拟、基于小扰度理论模型和大扰度随动模型的分析结果进行比较分析。结果表明,当摩擦系数按文献实验测值0.189取值时,有限元模拟、基于小扰度的理论模型和大扰度随动模型计算所得的刚度值均与试验所得的相近;卸载稳定段的刚度均明显小于加载稳定段的,是加载时的0.6倍左右。有限元模拟分析进一步阐明,在压紧弹簧变形过程中,压紧弹簧的截面存在转动,它与垫板之间的接触点并不是固定的,在加载和卸载过程中存在来回的径向位移。并且压紧弹簧接触面上的摩擦力方向是相反的,使得压紧弹簧在加载和卸载过程的刚度存在较大的差别。较小扰度理论模型、考虑压紧弹簧截面转动和接触点径向位移的大扰度随动模型所得的结果与有限元模拟更为接近。      

模拟水环境下的压紧弹簧刚度试验及计算模型的研究

在模拟水环境下,对堆内构件压紧弹簧的缩比试样进行了刚度试验,并与有限元模拟、基于小扰度理论模型和大扰度随动模型的分析结果进行比较分析。结果表明,当摩擦系数按文献实验测值0.189取值时,有限元模拟、基于小扰度的理论模型和大扰度随动模型计算所得的刚度值均与试验所得的相近;卸载稳定段的刚度均明显小于加载稳定段的,是加载时的0.6倍左右。有限元模拟分析进一步阐明,在压紧弹簧变形过程中,压紧弹簧的截面存在转动,它与垫板之间的接触点并不是固定的,在加载和卸载过程中存在来回的径向位移。并且压紧弹簧接触面上的摩擦力方向是相反的,使得压紧弹簧在加载和卸载过程的刚度存在较大的差别。较小扰度理论模型、考虑压紧弹簧截面转动和接触点径向位移的大扰度随动模型所得的结果与有限元模拟更为接近。      

螺旋管换热器传热管动力特性的试验及数值分析

介绍了模拟高温气冷堆蒸汽发生器螺旋式传热管的螺旋管动力特性试验模型;对单根螺旋管在不同支撑条件下的动力特性进行试验研究的方法;动力特性的一些规律;并用有限元方法对试验模型的固有频率进行了数据分析。由计算结果和试验结果比较看出,本文建立的有限元计算模型可对螺旋式传热管的固有频率进行有效的预测。     

SA335-P11钢高温断裂韧性试验中规则化方法的应用

运行温度下的弹塑性断裂韧性参数是核电厂含裂纹缺陷压力管道设计、评价和分析的重要数据输入。高温环境会对弹性卸载柔度法的准确性造成影响。基于载荷分离理论的规则化数据处理方法无需同步测量裂纹扩展量即可获得材料弹塑性断裂性能数据J-R阻力曲线,具有明显优势。根据美国材料与测试协会(ASTM)E1820标准,对核电厂主蒸汽管道材料SA335-P11钢的紧凑拉伸(CT)标准试样在280℃高温环境进行J-R阻力曲线测定。对试验载荷位移试验数据分别采用弹性卸载柔度法和规则化数据处理方法进行对比分析,验证在高温试验环境下的分析中规则化数据处理方法对传统弹性卸载柔度法的可替代性。     

乏燃料后处理屏蔽小室地震下安全性能分析

评估地震载荷下屏蔽小室的安全性能,需要检查屏蔽小室内部箱体结构的稳定性(滑移和倾覆)、完整性(应力和位移)以及地震载荷下外屏蔽层和箱体的密封性。本文采用有限元软件ABAQUS对屏蔽小室进行建模和抗震分析,包括对内部箱体在地震载荷下进行频谱分析,论证其整体的稳定性和完整性;分析外屏蔽层连接螺钉的受力来论证屏蔽层的密封性;分析箱体连接螺钉的受力来论证箱体的密封性。计算结果表明,地震载荷作用下屏蔽小室的整体强度是有保障的,密封边界螺钉的残余预紧力能够保证密封效果。     

安全壳喷淋泵的模态分析与试验验证

利用ANSYS有限元程序对安全壳喷淋泵进行模态分析,获得该结构的自振频率和振型;对安全壳喷淋泵进行动力特性测试并与分析结构进行比较。结果表明:理论计算的自振频率和振型与试验结果吻合较好,验证了该模型的有效性。     

柔度法计算Zr-4合金包壳管轴向裂纹应力强度因子的研究

基于虚拟裂纹闭合法，利用控制单变量变化的方法，对含对称双边缘裂纹的薄壁圆柱壳受对称集中力的情况进行了数值建模，得到了裂纹尖端的能量释放率，分析了Zr-4合金包壳管的预制裂纹长度和外部载荷对应力强度因子的影响作用。使用柔度法计算并获得了应力强度因子的近似计算公式，并与数值计算结果进行了对比验证，验证结果吻合较好。      

特殊机械密封结构的密封特性分析

使用MSC.Marc软件对国内某核电站改造项目中使用的特殊机械密封结构进行了有限元分析,对其密封特性有了新的了解.同时将计算结果作为后续应力分析和疲劳分析的边界条件,节省了试验或实际操作的成本.     

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.     

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。     

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.     

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.     

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.     

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.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

微型X射线管空气比释动能和能谱的测量

为研究微型X射线管的特性,通过电离室测量光管出射口30 cm远处的空气比释动能,使用高纯锗探测器分别测量了Ag过滤和Cu过滤下的X射线能谱。结果表明,空气比释动能随电流的增加有线性增加的趋势,能谱图明显的观察到银的两个特征X射线。完成了微型X射线管空气比释动能和能谱的测量方法以及实验测量的工作,为微型x射线管下辐射质的建立提够了条件基础。     

Gamma-ray attenuation technique for measuring void fraction in horizontal gas-liquid two-phase flow

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas-liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of 241Am with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas-liquid two-phase flow with high accuracy.