水压缸活塞环密封运动阻力研究

针对控制棒水压驱动机构单缸步进动态过程，根据水压缸活塞环密封机构的特点，分析水压缸单缸步进过程中运动阻力的来源，建立运动过程的动态理论模型。利用控制棒水压驱动机构单缸性能实验的结果，推导出水压缸单缸步进过程中运动阻力的变化过程。通过对运动阻力参数和步进过程中缸内压力以及步升速度动态参数的分析，得到了水压缸单缸步进过程中运动阻力的计算模型。由该模型计算所得步进动态位移曲线与控制棒水压驱动机构单缸步进实验位移曲线吻合得很好。本研究结果为控制棒水压驱动机构单缸步进过程的动态模拟以及控制棒水压驱动机构在步进过程中各部件的应力分析奠定了理论基础。     

水力步进缸静态保持流量的数值计算

以控制棒水力驱动系统为研究对象．采用商用流体力学计算程序CFX5对水力步进缸槽对孔部位,排气孔和迷宫漏流分别进行了数值计算．以获得步进缸的静态保持流量数值计算结果表明：槽对孔部位的流量是水力步进缸静态保持流量的主要部分．决定了水力步进缸静态保持流量随外套位置的变化规律;排气孔流量和迷宫流量所占的份额很小．其对步进缸静态保持流量的影响也很小：随着温度升高．水力步进缸的最小静态保持流量和最大静态保持流量都逐渐增大．这与实验结果吻合。     

水力驱动控制棒静态特性理论分析

对水力驱动控制棒步进缸的静态保持特性进行了理论分析。揭示了水力步进缸的静态保持流量范围和其随温度的变化规律 ,分析了静态特性与步进缸设计参数之间关系。结果表明 :步进缸的设计参数 ,重量、对孔、迷宫、放气孔尺寸等 ,确定了其静态保持流量范围 ;水密度随温度的变化 ,决定了最大、最小静态保持流量的温度特性     

控制棒水压驱动机构水压缸步降过程研究

水压缸是控制棒水压驱动机构的关键部件,根据水压缸步降运动过程特点,将水压缸步降过程缸内压力变化划分为步降前卸压过程和步降降压过程两个阶段,分别建立了两个阶段压力变化理论模型.其中,步降降压过程理论模型结合水压缸步降运动学模型,又得到了水压缸步降过程动力学模型.理论模型计算结果与控制棒水压驱动机构单缸步进性能实验结果进行了对比,结果表明,在实验配重载荷工况下,理论压力变化和位移曲线很好地符合了实验曲线,从而为水压缸步降压力变化过程影响因素的确定及控制棒水压驱动系统步进时间的获得提供了理论基础.     

水力驱动控制棒静态特性实验研究

对水力驱动控制步进缸的静态保持特性进行了大量实验研究。获得了水力步进缸的静态保持流量范围和其随温度的变化规律,分析了静态特性与步进缸设计参数之间的关系。结果表明：步进缸的设计参数（重量、对孔尺寸）确定其静态保持流量范围;随温度的升高、最大、最小静态保持流量有所增加;同一温度下不同步位上的静态保持流量范围趋于一致。     

水力驱动控制棒步进动态过程的研究

通过实验获得了水力驱动控制棒步进的动态过程.揭示了水力驱动控制棒的作用机理,详细分析了其动态特性与控制棒、组合阀性能参数及组合阀操作之间关系.结果表明:控制棒的步进是组合阀输出的流量脉冲、压力波,和步进缸运动产生的大阻尼压力振荡的共同作用过程;步进缸的性能参数限定了其静止平衡状态的流量范围,和其步进过程吸收流量脉冲和压力波的能力,而组合阀的性能参数决定了步进缸静止平衡、延时平衡、流量脉冲和压力波的量值,两者的合理匹配确定了控制棒的步进状态.     

水压缸活塞环密封流动阻力研究

根据控制棒水压驱动机构水压缸活塞环密封结构的特点,分析了水压缸活塞环的泄漏途径,建立了活塞环密封泄漏流阻的理论计算模型,并结合水压缸活塞环密封处的压差计算模型,推导出水压缸密封结构的流阻计算公式。利用控制棒水压驱动机构单缸性能实验的结果,拟合求得了流阻公式中的系数,并将公式计算流阻与实验结果进行了对比。结果表明:在实验工况下,二者吻合得很好。研究结果为控制棒水压驱动机构水压缸活塞环密封结构的设计和分析提供了理论基础。     

5MW THR控制棒水力驱动系统的设计及实验研究

控制棒水力驱动系统是不同于一般水动力堆使用的电磁-机械式传动系统的新型传动装置。它以反应堆冷却剂(水)为工作介质,经泵加压后,注入安装在压力壳内的水力步进缸,通过流量来控制水力步进缸外套作步进式运动,拖动与之相联的中子吸收元件。5MW HTR 是世界上首座使用这种传动的反应堆。采用该传动是为得到更好的安全特性,更可靠的驱动特性和良好的经济性。     

控制棒水压驱动系统冷态性能实验研究

控制棒水压驱动系统是清华大学为低温核供热堆NHR200发明的新型的内置式控制棒驱动技术,该驱动系统由水压驱动机构、组合阀、控制棒和缓冲器等组成。控制棒水压驱动系统冷态性能是控制棒步进时间和系统驱动压力选取的基础。本文分析了控制棒水压驱动系统的组成和工作原理,完成了全尺寸控制棒水压驱动系统冷态性能实验,包括水压缸最小落棒压力实验、提升缸带载步进实验和快速落棒实验等。在实验结果的基础上分析了关键特性参数的变化规律和机理。结果表明：最小落棒压力是保持驱动机构销爪正常工作所需的最小驱动压力,其对应于压力时程曲线上峰值波动过程的变化起点;步升和步降过程压力拐点分别对应位移到位点,随着驱动水压的增加,水压缸充压拐点压力逐渐增加,步升时间、充压拐点时间逐渐减少。实验研究成果为控制棒水压驱动系统的设计、优化和工程应用奠定基础。     

核电厂二回路热力系统的参数优化

提高核电厂的热效率可带来巨大的经济效益。本文采用定功率法对核电厂二回路热力系统进行热平衡计算。以二回路蒸汽压力和冷凝器传热端差为优化变量,在满足蒸汽发生器蒸汽产量、高低压缸功率比和低压缸排汽压力在某一范围内变化的约束条件下,寻求核电厂效率的最大值。文章对优化变量的敏感性进行分析,利用新型混合粒子群算法进行优化计算后,核电厂效率提高了0.5%,优化效果显著。     

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。     

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.     

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%。     

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.