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用有源(主动)的方法研究了贫化铀及其组合系统的中子诱发裂变缓发中子的探测技术。在不同质量和不同屏蔽体条件下测量和比较了贫化铀系统的裂变缓发中子随时间的分布,进一步分析了有源探测的入侵性和可核查性。探讨了采用缓发中子区分核与非核、贫化铀和浓缩铀系统的方法。 相似文献
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符合中子法测量贫化铀部件质量技术研究 总被引:1,自引:0,他引:1
分别采用有源(主动)及无源(被动)符合中子法研究了贫化铀半球壳部件质量的测量方法与技术。采用井型中子符合计数器对不同质量的贫化铀部件进行了符合中子计数的测量,主动法测量选取Am-Be源作为诱发中子源,通过屏蔽体减小源中子偶然符合计数的影响,根据测量结果求出的贫化铀部件线性拟合质量与标称质量最大相对偏差达11.71%,而被动法测量的拟合质量最大相对偏差仅为4.05%。证明了由于与主动法相比减弱了形状的影响,采用被动法测量贫化铀部件质量精度更高且更为可靠。 相似文献
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本文综述了利用~(252)Cf中子活化元素分析技术在工业过程控制中的应用现状、特点、前景和我国面临的任务。 相似文献
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缓发中子伴随核裂变产生,通过对它的测量估算核裂变数是一需实验检验的新方法。在中国原子能科学研究院微堆辐照235U样品,采用3He正比计数器测量缓发中子,并通过缓发中子数反推得到铀样品的总裂变数。利用高纯锗γ谱仪测量被辐照样品发射的缓发γ射线,通过缓发γ射线数得到样品总裂变数。对两种测量方法得到的结果进行了对比和分析,结果表明,用缓发中子法和缓发γ法对同一样品测量的结果一致,缓发中子法可作为一种辅助诊断方法。 相似文献
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在分析中子活化瞬发γ产生机理及瞬发γ射线强度计算方法基础上,提出了应用MCNP程序计算模拟核部件自发裂变中子活化放出瞬发γ能谱的直接模拟与分步模拟方法,对两种方法的计算结果及特点进行了比较分析。计算了模拟核部件核材料自发衰变产生的γ能谱,并与瞬发γ能谱进行了比较分析。本文结果可为核部件认证技术研究提供参考。 相似文献
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自1985年以来,仪器中子活化分析方法以及重建的500kW大叻核研究反应堆一直用于地质和环境样品的分析。该法具有灵敏度高、精度可靠,效率高的特点,所以满足了越南国内地质调查的需要。本文概述了越南在地球化学研究中应用仪器中子活化分析测定铀和钍含量所取得的主要结果。 相似文献
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蒙特卡罗方法模拟反符合屏蔽γ谱仪 总被引:1,自引:0,他引:1
本文用蒙特卡罗方法模拟反符合屏蔽γ谱仪中γ射线、电子及其二者级联簇射,给出了探测效率、沉积能谱、响应函数和能量分辨。计算结果同实验相符。可为设计反符合屏蔽γ谱仪提供理论数据。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(1):45-46
The effect of the presence of a reentrant hole for extracting the neutron beam from within experimental systems of two different geometries is analyzed theoretically with use made of multi-group 2- dimensional discrete Sn method without resorting to bold assumptions for neutron transport nor drastic simplification of geometry. One of the two experimental systems is a rectangular light water prism 12 cm high of 40 × 40 cm2 cross section, poisoned with Cd and/or In, and provided with a 1, 2 or 3 cm diameter reentrant hole. The other system is a 1″ thick natural uranium plate sandwiched between two layers of pure light water, each 4.6 cm thick, which also is provided with a 1cm diameter reentrant hole. The following is concluded by comparing the angular neutron flux with and without the reentrant holes. With the first experimental system, perturbations of the order 10~25% is caused, which is particularly strong below about 0.3 eV, except when the hole diameter is 1cm. The perturbation effect increases as the reentrant hole becomes larger in diameter and shallower in depth. In the case of the second experimental system, the effect results in about 2% increase of the neutron flux at the bottom of the reentrant hole when the bottom is located in the natural uranium plate. On the other hand, if the bottom is in the light water region, the neutron flux is reduced by about 2~4% at the peak of the thermal neutron spectra. 相似文献
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用MAT 262热表面电离型同位素质谱计测定了铀的同位素丰度比。环境样品采用HNO3 HF HClO4混合溶液溶解后,用TBP色层法进行分离纯化,再经电镀制备成供质谱用的测量源。结果表明,所测环境样品中铀的质量分数为:河水,8×10-8;长青树树叶,1×10-7;表层土壤,(5~11)×10-6。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(4):382-385
Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(11):488-494
A method was developed for recovering the fission product 133Xe from several kinds of reactor-irradiated U targets, including Al-U alloy, metallic U, and uranium oxides. In order to observe the release of 133Xe from U compounds at high temperatures, irradiated targets were heated at 500°~1,000°C in vacuum or under gas flow. The liberated 133Xe was trapped on charcoal beds, and the release rate of 133Xe from the compounds was determined by measuring the activity accumulating in the traps. More than 90% of the 133Xe was liberated from the alloy upon melting and from metal and uranium oxide upon oxidation. The isolated Xe was purified by a system embodying cold traps and cryogenic distillation. The final products were sealed in ampoules. They proved to possess radiochemical purity exceeding 99.9%, and less than 1 μ/ampoule (1 ml) of non-radioactive gaseous contaminants. 相似文献
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在裂变99Mo的生产工艺中,常用Al2O3色层法分离纯化99Mo。为建立Al2O3色层法从低浓铀(LEU)靶件中分离裂变99Mo的工艺,考察吸附时间、温度、酸度、预处理方式等对Al2O3吸附Mo效果的影响。研究采用Al2O3色层法从不同浓度HNO3溶液中分离Mo。测定Al2O3色层法对Al和主要杂质元素Sr、Ru、Zr、Te、Cs、I的去污系数。研究结果表明,在0.05~0.1 mol/L HNO3介质中Al2O3对Mo有出色的吸附性能,Mo吸附率在99%以上,在NH4OH溶液中Al2O3不吸附Mo。经500 ℃活化3 h预处理得到的Al2O3-C具有更大的比表面积,且在HNO3浓度大于0.1 mol/L时相比于150 ℃活化3 h预处理得到的Al2O3-B以及未经高温预处理得到的Al2O3-A对于Mo有更好的吸附性能。采用该工艺,通过Al2O3色层法从模拟的LEU靶件溶液中提取Mo,Mo回收率大于90%,Al2O3色层法对裂变杂质元素Ru、Sr、Zr、Te、Cs等的去除率均大于99.99%,对131I的去除率大于92%。由此可见,Al2O3在HNO3介质中对Mo的吸附率高,能够有效地去除99Mo产品中的杂质核素,适用于从低浓铀靶件中分离裂变99Mo。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(3):231-244
The extraction of uranium from sea water by the adsorption on the mixture of titanic acid and bentonite making the uranium rich deposit on the sea bottom is described. The purpose of this work is the minimization of energy required for contacting the vast volume of sea water with the adsorbent. Unique features of bentonite are applied to the coagulation of adsorbent forming the particles of suitable size in the sea water to make uranium rich deposit on the sea bottom close to the land. The concentration of uranium in the deposit is about 380 times that of sea water, and the loss of titanium is about 2% of the total amount of titanium which is used with the bentonite of ten times as much as it. The depths of sea necessary to make uranium rich deposit for the various conditions were calculated and the result was obtained that 50 m was sufficient for this method. As a trial of the second stage of concentration of deposited uranium, the continuous RIP method was carried out in counter-current fluidized bed which was operated without reversal of flow. The results reported in this paper are based on the laboratory scale experiments using the artificial sea water and on the calculations concerned with the rate of adsorption in agitated systems. 相似文献
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Vareeporn Ratnitsai Doonyapong Wongsawaeng Nares Chankow 《Journal of Nuclear Science and Technology》2013,50(9):1151-1161
Enhancement of uranium extraction from seawater using chromic-acid-treated amidoxime adsorbent was studied. Chromic-acid-treated amidoxime fibers were synthesized based on the simultaneous irradiation grafting method at a low temperature. Low-density polyethylene (LDPE) fibers were treated with chromic acid for up to 90 minutes. After the treatment, the fibers were submerged in 60:40 acrylonitrile:methacrylic acid monomer by volume and irradiated with 40 kGy γ-ray. The maximum grafting efficiency of about 90% occurred at 20 minutes of acid treatment time, as a significant enhancement of 30% compared to the literature-reported value of about 70%. When submerged in shallow seawater with an average temperature of 30 °C for 4 weeks, the amidoxime adsorbent exhibited the adsorption capacity of 2.06 g-U/kg-adsorbent, which was 37% higher than the literature-reported value. These significantly increased grafting and adsorption efficiencies were attributed to the increased surface area of chromic-acid-etched LDPE fibers. Moreover, for the submersion up to 8 weeks, the adsorption increased to 2.15 g-U/kg-adsorbent. The adsorption capacity was evaluated to reduce to about 65% after eight cycles of repeated usage. Uranium concentrations in Thailand's seawater collected at various depths and locations were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) to be about 3 ppb everywhere. 相似文献