相对论重离子核反应产生的中子能量和通量的固体径迹测定

在苏联杜布纳联合核子研究所同步稳相加速器上用CR-39探测器测量了44GeV ~(12)C+Cu(厚靶)核反应产生的中子能量和通量。测量表明.这一核反应释放的中子的平均能量为15.8±2.8MeV,当入射重离子数目为6×10~(11)时,与~(12)C束成～70°方向,距靶～60cm处的中子积分通量为(4.5±0.3)×10~9cm~2。这一方法可用来测量相对论重离子核反应释放的中子的角分布和每个入射重离子或每次核反应可产生的中子平均数目。     

合肥国家同步辐射实验室核物理实验区的辐射屏蔽设计和防护评价

本文主要介绍合肥国家同步辐射实验室(HNSRL)核物理实验区辐射屏蔽计算的方法及结果。对能量为400MeV、束流功率为6 kW 的电子束轰击靶时产生的轫致辐射和次级中子进行屏蔽计算;估算了靶室顶部次级中子的天空反射对周围辐射水平的影响;对靶室内的感生放射性气体(主要是~(13)N)的浓度进行了估计,确定了排放烟囱的高度。文中对靶室和核物理实验大厅提出了设置局部屏蔽和防护门等防护措施。     

600kV高压倍加器大厅内X-γ照射量率和能谱的初步测定

一、引言600 kV高压倍加器,通过T(d,n)~4He、D(d,n)~3He等核反应可产生14 MeV和2.5MeV的快中子,中子产额可达10~(11)n/s。其屏蔽设计情况,以及运行中可能产生的中子辐射场分布,在文献[1]中已有报道。在用该高压倍加器作引出质子束对光调束(质子束轰击铁靶)和离子注入等工作时,所产生的X、γ射线的照射将是主要的。测量和掌握高压倍加器上产生的快中子和X、γ     

重离子加速器在线测量实验区的屏蔽设计

本文主要介绍了重离子加速器核物理实验在线测量中为降低辐射本底而采用的多层组合屏蔽设计。计算了能量为700MeV 的~(12)C 重离子入射~(56)Fe 厚靶产生的中子产额(0.16n/离子)、能谱和角分布。采用铁(50 cm)、标准混凝土(150 cm)和硼砂层(1 cm)三层组合屏蔽,可在700MeV ~(12)C 重离子以7.5×10~(10)离子/s 流强入射~(56)Fe 厚靶下,把实验区的中子通量密度降低到1n/cm~2·s 左右。     

~(115)In中子非弹性散射截面的实验测量及蒙特卡罗修正

~(115)In是一种重要的活化材料,准确测量它的中子非弹性散射截面数据对中子注量监测具有重要意义。在四川大学原子核科学技术研究所2.5 MV静电质子加速器上,利用核反应D(d,n)~3He产生的单能中子,以~(197)Au作为标准,采用活化法测量了2.95 Me V、3.94 Me V、5.24 Me V能点的~(115)In中子非弹性散射截面。用Monte Carlo程序MCNPX(Monte Carlo N-Particle eXtended)对靶头材料、冷却水层和样品的包层材料等引起的多次散射效应及注量率衰减效应等进行了修正计算,得到最终结果与Loevestam的计算值符合较好,并且实验中可通过减小靶管、靶底衬、水层及样品的包层材料等厚度来减小多次散射效应和自屏蔽效应的影响。     

中能^12C重离子在Fe等厚靶上核反应的中子产额和能谱

本文调研了由测量和核内级联-蒸发模型理论计算得到的中能区重离子核反应中子发射微分截面数据,并依据这些结果计算给出了单核能为58.3和100MeV 的~(12)C 离子轰击~(56)Fe 厚靶产生的次级中子能谱、角分布和总产额。同时对现有数据做了较为细致的分析,为重离子的防护提供了一些基础资料。     

AB-BNCT中子靶物理设计分析

质子加速器适用于为硼中子俘获治疗提供中子源,其中子源强及能谱较反应堆中子源更具可调性。中子靶物理计算分析是加速器中子源设计的基础,为其提供粒子能量、流强等参数需求分析,并为靶体结构尺寸设计、中子慢化和屏蔽分析等提供前端参数。本文利用MCNPX蒙特卡罗程序,通过对质子打靶的中子产额和能谱、靶体能量沉积、打靶后靶材放射性活度和中子出射空间角分布等进行研究,提出能量2.5 MeV质子轰击100～200μm锂靶的设计,并用模拟计算数据论证其合理性。该设计中子源在1 mA流强质子轰击下,源强可达9.74×10~(11) s~(-1);拟设计15 mA、2.5 MeV质子束产生的中子源,在治疗过程中靶材放射性活度累积最大值约为1.44×10~(13) Bq。     

中能质子散裂中子源核子发射与能量沉积的计算

给出了用蒙特卡罗方法计算中能质子打在重核靶上产生的散裂中子源的物理图象、计算公式及所用核数据的来源,并对能量为800,1000,1500,2000MeV的质子打在~(186)W,~(208)Pb,~(232)Th,~(238)U靶上所产生的散裂中子源的中子数、能谱、空间分布、方向分布等进行了计算和分析。在计算中近似考虑了能量守恒,对于核反应结合能、原子核激发能及裂变能     

100千伏高压加速管

本文描述了一台100千伏高压加速管。在距离子源出口约2.5米远的靶上获得了大于150微安的离子流。靶点直径约7毫米。使用氘锆靶时,中子产额可大于5×10~6个/秒;使用氚锆靶时,中子产额可大于2×10~8个/秒。根据运行经验讨论了:(1)整流管工作情况;(2)在电压较低的加速器中(100—200千伏),电晕屏蔽罩的设计问题;(3)离子源寿命短的原因,并提出了改进方法;(4)聚焦过程中所遇到的一些问题和所作的一些实验结果;(5)水平型式加速管的优缺点。     

强流氘氚聚变中子源HINEG设计研究

强流氘氚聚变中子源HINEG(High Intensity D-T Fusion Neutron Generator)研发分两期:HINEG-Ⅰ为直流脉冲双模式,已成功产生中子强度1.1×10~(12)n/s的氘氚聚变中子,并实现连续稳定运行;HINEG-Ⅱ中子强度设计指标为10~(14)~10~(15)n/s量级,重点突破强流离子源和高载热氚靶技术。HNEG中子源可开展中子学方法程序与核数据、辐射屏蔽与防护、材料活化与辐照损伤机理和部件中子学性能等核能与核安全研究,同时也可在核医学与放射治疗、中子照相等领域拓展核技术应用研究。本文简要介绍HINEG总体设计方案与关键技术研究进展。     

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.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.     

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.