放射源远程遥控搜寻系统的设计及实验验证

设计了由辐射剂量仪、遥控机器人和手机或信号无线发送接收器等构成的远程遥控搜寻丢失放射源的机器人系统。采取两种方法(手机QQ视频和信号无线发送与接收)实现剂量仪数据和机器人坐标位置的远程无线实时获取。根据放射源辐射场分布规律,建立了辐射场剂量率分布数据库;设计了简单易行的机器人行走路线,快速获取9点剂量率数据;通过比较数据之间的关系和查询数据库确定放射源的具体位置,从而快速找到丢失的放射源,大大降低放射源对搜寻人员的辐射伤害,遥控距离达30 m,辐射剂量降低900倍。     

某高校放射源库辐射场的MCNP模拟及分析

采用非现场检测方法,给出某高校放射源库的辐射场分布,并计算出该放射源库的最大存储量,提出防护优化建议。利用MCNP(Monte Carlo N particle transport code)程序模拟计算放射源库辐射场分布,并与实测值对比,验证模拟值的可靠性。结果表明,MCNP程序模拟结果与现场实测值的误差基本保持在10%,能给出较精确的辐射场分布及源库最大存储量。结果提示:利用MCNP程序模拟放射源库及其周围辐射场,能在不进入辐射场的情况下,有效获取任意点处的剂量率;该高校放射源库采取的防护措施能保证在任意关注点处剂量率均小于国家标准限值;对于~(137)Cs的最大存储能力为4.88×10~(13) Bq,对于~(60)Co的最大存储能力为9.99×10~(10) Bq。     

泊松克里金算法在核辐射场重构中的应用研究

为验证泊松克里金法在核辐射场重构中的应用效果,本文对泊松克里金算法在辐射场剂量率插值计算中的计算原理进行了研究,结合代理模型对泊松克里金算法进行了求解。通过SuperMC软件建立虚拟辐射场,对泊松克里金算法的参数影响进行了分析,筛选出二次多项式基函数和GAUSS误差相关模型。采用6150AD-b闪烁体探测器对实际放射源进行测量,并利用实测辐射场剂量率数据和福岛周边空间剂量率数据对泊松克里金算法在核辐射场重构中的可行性进行了验证。结果表明：小范围简单辐射场中,样本数据量为网格点数的1/10时,平均相对误差在10%以内;大范围辐射场中,辐射热点区域略有偏移,平均相对误差为141.69%。以上结果表明,该方法在快速、低成本解决未知放射源辐射场的重构问题中有一定的潜力。     

密封容器中钚部件定位误差对轴对称性判断的影响研究

对称属性是武器用钚部件的一个重要属性.从武器上拆卸下的钚部件通常装在特定的密封容器罐内,当具有轴对称结构的钚部件的对称轴与容器罐对称轴重合时,容器罐外各对称探测点γ辐射场强度服从正态分布,根据γ辐射场强度分布的正态性可以判断容器罐内钚部件的轴对称性.容器罐内钚部件定位系统会有一定误差,当误差达到一定程度时,容器罐外γ辐射场分布将发生变化,各对称探测点7辐射场强度不再服从正态分布,进而会导致对钚部件轴对称性的误判.文章理论模拟了两轴平行偏离情况下容器罐外γ辐射场分布情况,用W检验法研究了钚部件定位系统误差对钚部件轴对称性判断的影响.     

通过γ辐射强度的变化规律定位核元件技术研究

利用标准面源来模拟核材料库的γ辐射场,从实验和理论两方面研究了移走某一放射源后四个不同监测位置γ辐射强度的变化规律。结果表明,移走监控对象中某一放射源后,不同检测位置γ辐射强度的变化规律是唯一的,并与理论计算符合得很好。据此完全可以确定核材料的变化情况。     

核辐射实验室环境辐射评估及其核信息共享平台构建

利用辐射仪测量实验室的辐射剂量率,得出核辐射测量实验室环境辐射场分布规律及核信息共享平台的构建。实验采用单一变量原则,利用不同屏蔽材料对不同放射源进行屏蔽。结果表明:核辐射测量实验室辐射场呈现辐射状分布,辐射剂量与距离,屏蔽材料的性质以及辐射时间有关,并提出了核辐射测量实验的优化方案:即将核辐射信号共享,将放射源、高压电源、闪烁探测器、前置放大器作为共享仪器,通过核信息共享器将核信息输送到各个实验台,然后对核信息进行测量、分析。     

~(137)Cs γ辐照器光阑的优化设计

利用蒙特卡洛方法模拟计算了不同锥角外光阑准直孔条件下~(137)Caγ辐射场的均匀性和散射剂量,对外光阑进行了优化设计。通过实验与模拟计算验证了经光阑准直限束后辐射场的径向均匀性,在距离放射源中心1 m处得到了均匀性好于99%,直径大于10cm的均匀野。~(137)Csγ辐射场轴向剂量的模拟计算值、测量值与平方反比规律理论值对比差异均小于1%。使用光阑后辐射场的均匀性及轴向剂量分布规律达到了建立~(137)Csγ标准辐射场的需求。     

均匀介质中γ成像三维图像重建

将γ相机的小孔成像模型类比成平行束模型,在代数重建法(ART)的基础上,加入衰减补偿,实现了均匀介质γ成像的三维图像重建。对比加入衰减补偿和未加入衰减补偿所重建放射源的位置和强度分布,得出介质对γ相机成像三维图像重建的影响:屏蔽介质只会影响重建后放射源的强度分布,不会影响放射源的位置分布。通过MC模拟数据的重建结果表明,本方案是切实可行的。     

核级设备鉴定装置γ辐射场计算平台开发

为更广泛、更方便地解决实际工作中的辐射场计算问题,采用有效可靠的计算模型以及计算机数据管理和数据可视化技术,并利用贪心算法快速求解复杂方程,开发了通用的γ辐射场计算平台,该平台实现了放射源管理、三维显示放射源布置和辐射场剂量率水平以及自动生成布置方案等功能。实验表明,用该平台自动生成的方案布置的γ辐射场能够满足核级设备γ辐照鉴定的要求。      

多放射源3D搜寻定位系统设计与模拟

为实现对多个放射源的搜寻定位,设计了用于确定放射源坐标的探测系统。探测系统基于方位角测量,用Na I探测器辨别γ放射源的方向。利用MCNP软件进行多放射源搜寻定位模拟实验,结果表明探测系统能够在多个放射源形成的辐射场中实现对放射源的搜寻并确定其空间坐标,且坐标偏差较小。探测系统可用于搜寻丢失的γ放射源并尽快确定其空间坐标。     

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。     

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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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.