共查询到17条相似文献,搜索用时 218 毫秒
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在军备控制核查技术领域,核弹头内部炸药的探测是一项重要的研究。本文利用GEANT4软件研究了基于武器级铀的核弹头(即铀弹头)内部炸药的被动探测法(利用铀弹头内部裂变中子作为中子源)的可行性,计算得到了从铀弹头中出射的γ射线能谱,能谱的形状与预期相符,但由于铀弹头内部裂变中子与炸药中~(14) N反应产生的特征γ光子的事例率太低,该方法可能不适用于铀弹头的现场测量。因此又利用GEANT4软件研究了铀弹头内部炸药的主动探测法(利用铀弹头外部的中子源对铀弹头进行辐照)的可行性。研究结果表明,主动探测法可在1h内实现对铀弹头内部炸药中~(14) N的探测和确认,进而能为判定铀弹头内部是否含有炸药提供重要依据。 相似文献
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核弹头的拆卸认证是核裁军和军控核查中的一项重要研究内容。核弹头拆卸后,核查方将对拆卸出的特殊核材料和高爆炸药进行探测和认证,确保两者来源于核弹头。本文着重研究铀弹头(基于武器级铀的核弹头)内部拆卸出的炸药的认证方法,提出基于中子辐照法的炸药认证方案,并建立基于Geant4软件的数值模拟计算平台,利用该平台对该方案的可行性和效果进行模拟计算研究。研究结果表明,核查方应单方面设定辐照时间,设置适当的核弹头拆卸时间,并探测拆卸出的炸药中13N和11C核素的β+衰变,即可区分真实铀弹头中拆卸出的炸药和炸药赝品,进而为判断炸药是否来源于铀弹头提供重要依据。 相似文献
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一、氡及其子体的来源和放射学特性在本世纪初发现了放射性惰性气体氡,氡来自~(238)U衰变系中~(226)Ra的衰变,氡衰变生成四种短寿命放射性核素(图1),再进一步衰变,最后到铅的稳定同位素~(206)Pb。土壤和岩石中的镭是氡气的主要来源。在铀矿山和某些非铀矿山,由于矿石中含有镭,井下氡浓度很高,如通风不好,氡浓度会更高。 相似文献
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短寿命放射性核素~(11)C、~(13)N、~(15)O、~(18)F都是缺中子型核素,产生β湮没辐射,从而产生方向相反,角度为180°±0.25°的两个511keV的γ光子,具有高灵敏度、高分辨率的正电子发射型计算机断层(PECT),可采用符合线路进行探测。由于~(11)C、~(13)N、~(15)O是人体组织、天然与合成药物的组成元素,而~(18)F则可代替H、卤素、OH基而不改变药物的生物活性,因此,这类药物可研究其在体内的生理、生化、病理过程,其显像不仅是形态型而且是功能性的;不是二维平面显像而是三维立体显像。 相似文献
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中子照射稳定核素产生的放射性核素,其中有些与铀的裂变产物中的放射性核素是相同的,例如由(n,γ)反应产生的放射性核素:~(140)La、~(141)Ce、~(143)Ce、~(147)Nd等几十种核素都可在铀的裂变链中找到。因此,如果样品中含有铀,就会干扰这些核素的测定。地质样品中的花岗岩,其平均铀含量是3~4ppm;主要类型沉积岩中铀含量也在0.1~10ppm;铀在水中含量为1.5~8μg/l;就是在正常人的血液中还含铀0.9~1.8ng/l。因此,用中子活化分析测定质量数为70~160之间的核素时,必须注意裂变产物的可能干扰。 相似文献
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在中国原子能科学研究院提议的串列加速器升级工程中,将建造一台100 MeV强流负氢回旋加速器。作为必要的预先研究,我们计划研制其中心区模型,磁钢度为0.455 T·m。该中心区模型可将负氢离子加速到10 MeV,除了作为强流回旋加速器的先进技术研究外,还可用于生产PET常用的超短寿命放射性核素:~(11)C、~(13)N、~(15)O和~(18)F,由于它的高流强,将会有更高的放射性核素产额,预计一台这样的加速器,将能满足国内任何一个城市对~(18)F的需求。 相似文献
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为了对环境中放射性污染水平进行有效监测,需要对环境样品中铀放射性核素进行分析。本实验采用浓硝酸溶液加热浸取样品中的铀,UTEVA树脂对铀进行吸附并用稀盐酸溶液进行解吸,有机物TTA萃取制成α测量源,通过示踪剂铀-232的计数来校正铀(铀-234、铀-235和铀-238)的化学回收率。本方法实现了对环境样品中铀放射性核素的快速分析,同时进行了条件实验,确定了最佳测量条件:浸取液为8.0 mol/L硝酸溶液,解吸液为0.01 mol/L盐酸溶液,示踪剂用量为180 mBq。结果表明,当样品用量为0.5 g,测量时间100000 s时,该方法的最小可探测活度浓度为0.13 Bq/kg,满足环境样品中铀放射性核素的分析要求。 相似文献
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In the current situation of the increasingly serious terrorist activities, explosives were hidden inside the package by terrorists. The main task for international anti-terrorism is to detect the explosives hidden in the package timely and precisely. The chemical elemental composition of explosive is mainly C, H, O and N. Daily necessities are also composed of these four elements. There is a great difference for elemental ratio between daily necessities and the explosive. The atomic density and relative content of C, H, O and N can be determined, which can distinguish explosive from organics. A removable explosive detection device based on tagged neutron method was developed. The tagged neutron method (TNM) technique is mainly based on the principle of coincidence to reduce the background of spectrum. The contents of chemical elements (C, N, O) and the ratio of C/O and C/N in the explosive were determined by analyzing the characteristic gamma energy spectrum to determine the existence of explosives. The ING-27 neutron generator and Φ76×76 mm LYSO scintillator detectors are selected in the experiment. Explosives detection devices are used to measure the sample of explosives surrogate, organic and explosives placed behind organic in the package. The results show that this method can effectively distinguish between explosive TNT and organic dry milk powder. 相似文献
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The detection technology of concealed bulk explosives is related to social security and national defense construction and has important research significance. In this paper, an element analysis method of concealed explosives based on thermal neutron analysis is proposed.This method could provide better reconstruction precision for hydrogen, carbon, and nitrogen ratios, making it possible to discriminate explosives from other compounds with the same elements but different proportions, as well as to identify the types of concealed bulk explosives. In this paper, the basic principles and mathematical model of this method are first introduced, and the calculation formula of the element number ratio(the ratio between the nucleus numbers of two different elements) of the concealed explosive is deduced. Second, a numerical simulation platform of this method was established based on the Monte Carlo JMCT code. By calibrating the absorption efficiencies of the explosive device to c rays, the element number ratios of a concealed explosive model under the irradiation of thermal neutrons were reconstructed from the neutron capture prompt c-ray spectrum. The reconstruction values were in good agreement with the actual values,which shows that this method has a high reconstruction precision of the element number ratio for concealed explosives. Lastly, it was demonstrated using the simulation study that this method can discriminate explosives,drugs, and common materials, with the capability of determining the existence of concealed bulk explosives and identifying explosive types. 相似文献
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Utilization of nuclear explosives can produce a significant amount of energy which can be converted into electricity via a
nuclear fusion power plant. An important fusion reactor concept using peaceful nuclear explosives is called as PACER which
has an underground containment vessel to handle the nuclear explosives safely. In this reactor, Flibe has been considered
as a working coolant for both tritium breeding and heat transferring. However, the rich neutron source supplied from the peaceful
nuclear explosives can be used also for fissile fuel production. In this study, the effect of using thorium molten salts on
the neutronic performance of the PACER was investigated. The computations were performed for various coolants bearing thorium
and/or uranium-233 with respect to the molten salt zone thickness in the blanket. Results pointed out that an increase in
the fissile content of the salt increased the neutronic performance of the reactor remarkably. In addition, higher energy
production was obtained with thorium molten salts compared to the pure mode of the reactor. Moreover, a large quantity of
233U was produced in the blanket in all cases. 相似文献
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快中子活化分析检测爆炸物方法研究 总被引:1,自引:1,他引:0
叙述了快中子活化法检测隐蔽爆炸物的原理、方法及其优点。采用K-400高压倍加器产生的14MeV快中子对TNT、黑索金、硝胺及土制炸药等4种炸药、10余种常见物品和用土壤层覆盖的TNT样品进行快中子活化分析,测定各种样品的氮氧含量,建立被测物单位质量氮和氧计数率的二维分布,取得了爆炸物识别特征区,并用计算机模式识别方法进行判别。结果表明,此方法误判率和漏判率较低。Monte-Carlo模拟结果显示,在距中子源15m以外,基本无辐射剂量,被测物经检测1h后,总剂量小于环境本底剂量。本方法可用于远程控制快中子活化多探测器阵列检测爆炸物。 相似文献