CARR堆冷中子导管的模拟和优化设计

应用蒙特卡罗模拟技术对中国先进研究堆两条冷中子导管的设计方案进行了模拟和优化研究。 对于特征波长为0.2 nm的冷中子导管中CNG1,研究了堆内导管、弯导管和直导管分别使用~(58)Ni和超镜作镀膜材料的不同设计方案,表明超镜导管不仅可以提高中子特别是短波中子的传输效率     

中子三轴谱仪输入谱模拟与优化计算

根据冷中子源及其后续中子导管的布局与参数,采用蒙特卡罗方法模拟计算了中子三轴谱仪的输入谱,获得了中子束均匀性、发散度及注量率等参数。模拟结果表明：冷源与导管人口间距离L不宜小于0.1m,在距离为0.5m时导管出口处注量率达到最大3.96×10^8cm^-2s^-1。;中子注量率及发散度均随导管超镜因子m增大而增大,m值由1.5增大到3后,其水平方向的发散度几乎不变,垂直方向最大发散度增大约87.7％,注量率增大25％;垂直方向和水平方向的发散均可以用高斯分布来描述,但水平方向的发散伴有离散峰;在m为1.5,L为2m情况下,束流水平和垂直方向的最大发散度分别为0.85°和0.81°,中子注量率为2.86×10^8cm^-2s^-1;得到了针对三轴谱仪的导管优化参数。     

冷中子导管模拟和参数优化计算

根据冷中子源及后续中子导管的布局参数,采用蒙特卡罗方法模拟计算了冷中子导管C3出口处中子柬均匀性、准直性及注量率等数据。优化表明：a）冷源与后续导管入口间距离应尽可能短;b）中子注量率及发散度均随导管超镜因子m值增大,m值由1．5增至3．0,其Y方向发散度增大24％,注量率提高61％;c）垂直于导管弯曲面方向的发散可以用高斯分布来描述,而导管偏转方向则呈条纹状发散;d）在m=1．5、冷源与堆内导管入口距离为2．29m情况下,束流垂直发散宽度为O．86°,中子注量率为2．44×10^2cm^-2．S^-1。     

中子反射谱仪前端导管优化

基于两种中子反射谱仪设计(A:前端为8.0 m垂直聚焦导管,入口200mm,出口40 mm;B:前端为1.6+3.4m水平偏转垂直聚焦导管,入口100mm,出口50mm),对其前端偏转/聚焦导管进行了中子束模拟,结果表明:1)在特征波长为0.4 nm的冷中子导管末端,没有必要再次偏转束流以减低本底;2)与建议方案相比,概念设计中的注量下降了52.8%,而水平方向发散度增大了24.1%,垂直方向发散度减小60.7%;3)聚焦导管长度应不低于6.0 m,导管聚焦超镜m值在2.0-2.5最佳,两侧超镜m值对束流几乎无影响,使用中子束高度应不低于150mm可达到较好的注量率和发散度.     

中国先进研究堆冷源尺寸对冷中子导管出口处中子注量率的影响

应用蒙特卡罗方法研究了中国先进研究堆冷中子源尺寸对58Ni和超镜冷中子导管出口处中子注量率的影响,使用2个不同软件获得了一致的模拟结果。对于58Ni导管,需要18cm×30cm的冷中子源尺寸才可使积分中子注量率和直到2nm波长的中子注量率达到饱和,对于m=2的超镜导管对应的尺寸为22cm×36cm。     

中国先进研究堆中子散射工程中子导管模拟研究

为使依托中国先进研究堆（CARR）进行的冷中子散射实验拥有更高质量的中子束流,本工作对中子散射工程中的中子导管系统各参数进行分析研究,并首次在国内应用等效中子导管理论,结合解析计算确定出优化的导管方案。同时,应用VITESS程序对各导管方案得到的中子束流进行了模拟,在综合考虑导管系统几何布局及中子束流的发散度影响后,探讨出若干符合实际的设计方案。尔后,利用导管位置计算程序NGPS,计算出各导管方案中每个导管单元的位置坐标。最终,根据各项指标对模拟的各导管方案进行对比,优选出CNGA、CNGB、CNGD3套中子导管系统的最佳参数,为即将进行的中子导管系统的设计和安装提供理论参考。     

75 MeV/u~(12)C离子束在辐射生物实验区产生的中子角分布

本文应用Ａｌ为阈探测器在兰州重离子研究装置（ＨＩＲＦＬ）的辐照终端上研究了７５ＭｅＶ／ｕ１２Ｃ离子束在辐射生物实验区产生的能量大于６ＭｅＶ的中子角分布。实验中束流经２４μｍ的Ｎｉ窗及由１０μｍ镀金的Ｍｙｌａｒ膜组成的平行板电离室后进入实验区,７个２０ｍｍ×５ｍｍ的阈探测器放置在距Ｎｉ窗２５ｃｍ处的不同角度上（６．５°～３６．０°）,束流强度为３ｎＡ,活化样品测量用高纯锗探测器。结果表明,实验区产生的中子具有明显的前冲分布,测得的中子注量率分布,在与束流方向夹角６．５°～３６．０°范围内,大致呈指数衰减。这为进一步开展的重离子治癌研究提供了辐射防护的实验依据。     

导管中冷中子传输过程的数值模拟

中子导管是利用中子全反射原理将中子束以很小的传输损失传递到远离中子源处的物理装置。利用蒙特卡罗方法模拟中子在导管中输运过程,在中子导管的设计和实验应用中可发挥重要作用。某座反应堆上正建设包括有3束导管的冷中子导管系统,以蒙特卡罗方法为基础,开发出该导管系统的数值模拟程序,并利用该程序计算得到该导管各个输出口的中子注量率及能谱分布,为布置在导管周围的中子散射谱仪和其它应用装置的设计提供了必要的输入条件。     

用大角度伴随粒子法测量聚变中子产额及其校对实验

描述了用大角度（178.2°）伴随α粒子方法测量绝对D-T 聚变中子产额及其校对实验。为此,设计和加工了一套三叉管校对靶室,α粒子探测器分别置于与D∧ 束成90°、135°和178.2°的方向上,测量和比较了三个方向的α粒子谱和绝对中子产额。分析了实验误差来源,并对实验结果进行了讨论。     

CMRR中子自旋回波谱仪引束导管模拟研究

中国绵阳研究堆(China Mianyang Research Reactor,CMRR)采用由弯导管和直导管组成的引束导管偏转第三条冷中子管(C3)冷中子束第二端口(C32)上部区域内的中子束流,为自旋回波谱仪提供中子束。应用中子射线追踪程序McStas 2.5对引束导管进行蒙特卡罗模拟,从弯导管通道个数、曲率半径以及超镜因子三个方面,考察引束导管设计方案以验证其设计可行性。结果表明:1)弯导管通道个数设计值合理;2)弯导管曲率半径取值在谱仪与屏蔽体安装空间可接受情况下,应尽量大;3)弯导管超镜因子取2.5时,引束导管出口与样品处中子通量可达到最大强度。根据模拟计算结果,弯导管超镜因子设计值偏大,引束导管设计方案总体具有可行性。     

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.     

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.