核电厂安全壳极限抗压承载力及影响因素分析

核电厂安全壳极限抗压承载力、影响因素及其规律是核电结构安全评估、事故处理和结构设计的关键问题。本文以某安全壳为例,采用损伤塑性模型模拟混凝土的力学性能,双线形应力-应变模型模拟钢衬里和预应力钢束的材料非线性,基于ABAQUS软件系统地分析了核安全壳极限抗压承载力,并给出了结构自重、预应力、钢衬里等因素的影响规律。研究表明,当内压增大到0.87 MPa时,安全壳筒壁上部混凝土开始进入塑性;当内压增大到1.02 MPa时,钢衬里最大拉应变超过限值3 000×10-6,安全壳达到极限状态。在各种影响因素中,预应力和钢衬里对安全壳的极限内压和破坏形式起着关键作用。本文研究结果对核安全壳极限承载能力分析、结构设计和安全评定等方面具有一定的参考价值。     

考虑预应力损失影响的安全壳安全性能研究

预应力损失对安全壳在内压作用下的安全性能影响不可忽略，本文通过考虑安全壳不同龄期下的预应力损失来研究安全壳在设计基准期内40年及设计基准期后60年不同内压水平作用下的安全性能。采用ABAQUS有限元软件建立了精细化安全壳三维有限元分析模型，通过非线性有限元方法分析了钢衬里屈服、预应力筋屈服、混凝土裂缝演化等性能指标。研究结果表明，考虑预应力损失后，安全壳混凝土开裂与钢衬里失效时，所能承受的内压荷载减小；安全壳在极限内压作用下的变形表现为穹顶向外膨胀以及洞口向内收缩；安全壳穹顶部分在极限内压下破坏严重；考虑预应力损失后，安全壳变形明显增大。但安全壳在设计内压(0.4 MPa)作用下仍有足够的安全裕度。     

严重事故下预应力混凝土安全壳非线性分析及性能评估

预应力混凝土安全壳作为核电厂重要防泄漏屏障,对保证核电厂正常运行、确保人员安全至关重要。本文基于顺序热力耦合方法对严重事故工况下预应力混凝土安全壳进行非线性有限元分析,考虑了温度和内压荷载共同的影响,分析了安全壳结构典型不连续区域和连续区域的位移响应。研究表明:安全壳混凝土不连续区域位移响应沿厚度方向上差异较为显著,而连续区域处的差异相对较小;安全壳泄漏失效模式由设备闸门位置控制,50%和95%分位水平的内压分别为1.266 MPa和1.072 MPa;破口失效模式由筒体某一位置控制,50%和95%分位水平的内压分别为2.224 MPa和1.883 MPa;本文所分析的预应力混凝土安全壳的内压承载力满足最小安全裕度不小于2.5的要求。      

核岛安全壳截锥体中模拟浇筑自密实混凝土时钢衬里的应力监测与分析

为保障自密实混凝土浇筑过程中核岛安全壳的完整性和稳定性,建立了安全壳截锥体的同尺寸1/8模型,进行自密实混凝土现场浇筑,并对其中钢衬里表面的应力进行监测和模拟计算。研究结果表明,随着自密实混凝土浇筑高度的增加,钢衬里所受应力逐渐增大,在浇筑至应变点位置时,钢衬里应力值发生突增;而采用水平角钢加固后对钢衬里横向和竖向表面应力都具有明显的改善作用。     

某核电厂LOCA下预应力混凝土安全壳响应规律初探

核电厂LOCA发生后,预应力混凝土安全壳结构内温度场分布具有明显的非线性特征,但现行的混凝土安全壳设计规范未对LOCA下温度和应力的组合作用提出具体的计算方法。基于用ANSYS程序建立的包含预应力钢束的混凝土安全壳结构的有限元模型,本文计算了LOCA下不同时刻安全壳壳壁内的温度场分布,并与理论值进行了比较,验证了计算模型的正确性。初步分析了高温、高压作用下安全壳结构变形的规律,总结了混凝土温度效应和预应力系统的作用,可为安全壳结构设计提供参考。     

核电厂安全壳结构钢衬里力学行为研究进展

钢衬里作为核电厂安全壳结构的重要防泄漏部件，对保证核电厂安全运行及人员安全至关重要。本文从试验研究，数值模拟分析以及理论分析三方面对钢衬里力学行为相关研究进行系统总结。综合国外著名安全壳模型试验结果，阐述了钢衬里在事故压力荷载下的撕裂机理。详细对比多轴应力状态系数的不同计算方法，同时指出目前关于钢衬里力学行为问题研究不足及需要深入研究的问题。通过文献综述对比发现：局部区域变形集中是造成钢衬里撕裂的主要原因，钢衬里局部连接几何条件、锚固系统以及钢衬里与混凝土之间相互作用是影响钢衬里撕裂的主要因素。三种钢衬里撕裂准则对应考虑的影响因素不尽相同，钢衬里多轴应力状态系数三种计算方法差别较大，综合相关钢衬里撕裂判定准则研究成果，提出了建议的钢衬里撕裂准则，且本文建议的钢衬里撕裂准则与美国核管会导则RG.1.216准则吻合程度很好。此外，深化钢衬里撕裂机理研究，在此基础上发展安全壳泄漏概率安全评价方法是后续研究工作的重点。     

秦山核电厂预应力混凝土安全壳的结构研究和设计

回顾和总结了秦山核电厂的预应力混凝土安全壳设计全过程,简单地介绍了对预应力钢丝束的试验,描述了结构型式、设计基准和分析方法,并扼要地指出了混凝土防裂考虑和后张体系及钢衬里设计的概貌,介绍了对秦山核电厂安全壳结构极限承载性能所进行的模型试验及非线性分析研究。最后介绍了秦山核电厂安全壳的整体性试验,指出秦山核电厂的安全壳试验实测值与预期值相符,结构性能良好,气密性也完全符合要求。     

百万千瓦级核电厂安全壳结构设计与试验研究

通过建立符合先进核电厂安全壳结构特点的线性和非线性有限元分析模型,得出合理的安全壳预应力张拉顺序,计算出安全壳在设计事故内压、严重事故内压状态下的工作生能及其极限承载能力,并与110的大比例尺结构模型试验结果相互比较,取得一致的结论先进核电厂安全壳符合国际上极限承载力≥25倍设计内压的合格标准.从而验证了先进核电厂安全壳概念设计的合理性.     

某核电机组安全壳打压试验期间安全壳外加应变计数据分析研究

全寿命监测安全壳的变形是评估其安全状况的重要手段,对于预埋监测应变计的失效则需在壳外壁加装应变计,然而,替代应变计的监测数据是否能合理反映内部变形规律是亟待解决的关键问题。以CPR1000某核电机组为研究对象,基于ANSYS建立了安全壳结构三维精细化模型,采用实体力筋法和降温法来模拟预应力筋以及预拉力的施加;通过整体式模型考虑混凝土中普通钢筋的影响,以及节点耦合来实现钢衬里与混凝土的相互作用。进而结合该机组大修打压试验期间预埋应变计的监测数据,验证所建立模型的合理可靠性;并通过对混凝土和预应力筋的参数敏感性分析,进行模型材料参数的修正。最后,在典型荷载作用下探讨安全壳结构内部和外部变形之间的关系及变化规律。计算结果表明:当混凝土弹性模量取45 GPa,其他参数取初始值时,修正模型的计算应变值与现场监测结果吻合较好,且沿远离设备舱口的壁厚呈线性分布。在安全壳外墙上增加应变片的监测结果可以很好地反映内部变形规律,说明替代方案是可行的。     

基于ANSYS的核电厂安全壳结构非线性有限元分析

对核电厂预应力混凝土安全壳结构进行了内压作用下的非线性有限元分析.详细介绍了ANSYS中的混凝土单元SOLID65及混凝土材料的本构关系,并对非线性求解过程中影响收敛的因素进行了分析；同时,以福清核电厂5、6号机组内层安全壳为工程实例进行有限元计算.结果表明,15 m至30 m标高范围内的径向位移大于其他高度的径向位移,标高25 m左右径向位移最大；内压加至0.42MPa,模型结构仍处于受压状态,满足使用要求.分析表明,福清核电厂5、6号机组安全壳结构在设计内压作用下是安全的,可为安全壳整体性试验提供参考.     

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。     

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.     

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.     

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

正~~     

Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.