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1.
In this study total twenty samples (eight reference materials and twelve sediment samples) were analysed for their uranium content which is in the range of 1–17 μg/g, by neutron induced fissionography (NIF) method using solid state nuclear track detectors (SSNTDs) in comparison with the results of neutron activation analysis (NAA), delayed neutron counting (DNC) technique or fluorometric method. It is found that NIF method using SSNTDs is very sensitive for analysis of uranium.  相似文献   

2.
A perturbation method is proposed to obtain the effective delayed neutron fraction β_(eff) of a cylindrical highly enriched uranium reactor.Based on reactivity measurements with and without a sample at a specified position using the positive period technique,the reactor reactivity perturbation △ρ of the sample in β_(eff) units is measured.Simulations of the perturbation experiments are performed using the MCNP program.The PERT card is used to provide the difference dκ of effective neutron multiplication factors with and without the sample inside the reactor.Based on the relationship between the effective multiplication factor and the reactivity,the equation β~(eff)=dκ/△ρ is derived.In this paper,the reactivity perturbations of 13 metal samples at the designable position of the reactor are measured and calculated.The average β_(eff) value of the reactor is given as 0.00645,and the standard uncertainty is 3.0%.Additionally,the perturbation experiments for β_(eff) can be used to evaluate the reliabilities of the delayed neutron parameters.This work shows that the delayed neutron data of ~(235)U and ~(238)U from G.R.Keepin's publication are more reliable than those from ENDF-B6.0.ENDF-B7.0,JENDL3.3 and CENDL2.2.  相似文献   

3.
The experiments on transmutation of 129I and 237Np using uranium-lead targets surrounded by a paraffin moderator were performed at the Joint Institute for Nuclear Research (JINR, Russia). The targets were irradiated by 1.5 GeV and 7.4 GeV protons at the Synchrophasotron of JINR. In the frame of present work spatial and energy distributions of neutrons on the surface of the paraffin moderator were measured using SSNTD technique. It is shown that measured values of spetral indices do not pretend on the energy of incident protons but depend on the target composition. The presence of the uranium insertion softens neutron spectra.  相似文献   

4.
微波消解/ICP-MS测定水系沉积物中的9种重金属元素   总被引:8,自引:0,他引:8  
优化了微波消解进行沉积物样品前处理的方法,选择了HNO3-H2O2-HF体系。以Ge,In,Bi为内标元素,建立了电感耦合等离子体质谱(ICP-MS)同时测定Cr,Mn,Ni,Co,Cu,Zn,Cd,Sb,Pb九种重金属元素含量的方法。该方法的相关系数都在3个9以上,测定了国家标准物质ESS-1GSBZ50011-88土壤中的元素,测定值与标准值或参考值一致,相对标准偏差0.48%~5.73%,加标回收率98.0%~100.7%,检出限在0.011~0.328μg.L-1。利用建立的方法测定了白洋淀11个代表性点位的水系沉积物中的九种重金属元素含量,为环境中土壤及水系沉积物中重金属元素含量的测定提供了可靠的分析方法。  相似文献   

5.
The knowledge of the isotopic composition of man-made transuranium elements (TUE) in the environmental samples is of great interest because, on the basis of these data, statements about the origin of the TUE can be made. One of the most radiotoxic elements released during reactor accidents and nuclear weapons tests was plutonium with the alpha emitters 238Pu, 239Pu, 240Pu, 242Pu and the beta-emitter 241Pu which decays into 241Am. The determination of plutonium in “hot” particles from the Chernobyl reactor was accomplished by means of solid state nuclear track detectors registering the alpha particles and by alpha spectroscopy after chemical treatment. Furthermore, in order to perform a complete analysis of the isotopic composition one of the “hot” particles has been investigated by resonance ionization mass spectrometry which possesses an excellent sensitivity and a good isotopic resolution.  相似文献   

6.
Sealed can- and alpha-autoradiography techniques were used to estimate the effective and real contents of Ra-224 respectively in Egyptian black sand samples collected from Rosetta City in the Nile Delta at the North Coast of Egypt. The effective Ra-224 content was found to be 15 ± 3 Bq · kg?1. From the average chemical composition of the black sand samples, the range-energy relation for the alpha-particles of the thorium series was calculated. Assuming radioactive equilibrium, the real Ra-224 content for samples collected from different regions were found to range from 90 to 900 Bq · kg?1. As a result, the total emanation power was measured and then used to estimate grain diameter of the black sand. The average mass exhalation rate of the different locations in Rosetta City was also estimated.  相似文献   

7.
The quartz glass open chromatographic columns with thermal gradient, which usually were used for the investigation of chemical properties of short-lived Z104 nuclides, were first used as the track detectors of spontaneously fissioning isotopes of elements 104, 105 and 106. The recoil nuclei of these elements were captured by the flow of gaseous chlorides then go to the quartz tube with reducing thermal gradient 400°C-100°C. The quartz tube was etched in 40% HF. The tracks due to spontaneous fission of isotopes 259104, 262105 and 263106 which were etched at the internal wall of quartz tubes were counted under optical microscope.  相似文献   

8.
The activity concentration of natural (238U, 232Th, and 40K) and artificial (137Cs) radionuclides was determined in 50 samples (obtained from the same station) from various species of mushrooms and soil collected from the Middle Black Sea Region (Turkey). The activities of 238U, 232Th, 40K, and 137Cs were found as 84 ± 16, 45 ± 14, 570 ± 28, and 64 ± 6?Bq?kg–1 (dry weight), respectively, in the mushroom samples and as 51?±?6, 41?±?6, 201?±?11, and 44?±?4?Bq?kg–1, respectively, in the soil samples for the entire area of study. The results of all radionuclide activity measurements, except those of 238U and 232Th in the mushroom samples, are consistent with previous studies. In the soil samples, the mean values of 238U and 232Th are above the world mean, and the activity mean of 40K is below the world mean. Finally, the activity estimation was made with both the soil and mushroom samples for unmeasured points within the study area by using the ordinary kriging method. Radiological distribution maps were generated.  相似文献   

9.
The method of 239Pu minor content determination based on subsequent activation with thermal neutrons and gamma-rays was applied for preparations chemically separated from soils, water, river sediments and some living species. The obtained level of sensitivity for routine analysis is proved to be equal 10−13 gram Pu per gram of sample.  相似文献   

10.
222Rn dissolved in drilling fluids of the KTB (Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland) pilot hole has been determined using solid state nuclear track detector (SSNTD) technique:The α-sensitive SSNTD CR-39 was used to measure the a-activity of 222Rn. Well-defined conditions for Rn-measurements could be established by employing a mica nuclear track microfilter to separate the detector containing air volume from the volume containing the water. This technique has been applied to determine quantitatively the 222 Rn-concentration as a function of depth of the borehole down to 4000 m.  相似文献   

11.
Severe radiation damages with the following substitution of connective tissue are the effect of high doses in microvolumes of the thyroid. Calcium, strontium and uranium deposited into these sections was more as compared to a normal tissue of the thyroid. An estimation of the microdistribution of fissile radionuclides was carried out using the method of fragmental radiography. The analysis of tracks done visually using a microscope magnification of 300 revealed the local density of fission fragments up to 103 mm−2. The irradiation of the surrounded cells which contain the hidden genetic damages, initiated by radioiodine, does not exclude their possible promoter role in thyroid cancerogenesis.  相似文献   

12.
CR-39 and LR-115 plastic nuclear track detectors in the can-technique have been employed in the field measurements of radon exhalation, Ra-226 and U-238 content in dry-soil air at numerous regions in Sudan (the Blue and White Nile and Mogran regions). Measurements gave an average radon exhalation from the soil to the atmosphere and Ra-226 content of (23.4 ± 2.60) kBq · m?2 and (123 ± 13.65) Bq · kg?1 respectively. A polyethylene permeable membrane cover was used to eliminate the contribution of thoron activity inside the can. Assuming a radioactive equilibrium between the U-series, the average U-238 content in the soil was found to be (9.92 ± 1.01) ppm. This survey may be used for uranium prospection in soil.  相似文献   

13.
Neutron scattering experiments were performed on 6 m LiCl solutions in order to obtain the solvation structure around the chloride ion. Molecular dynamics simulations on systems mirroring the concentrated electrolyte conditions of the experiment were carried out with a variety of chloride force-fields. In each case the simulations were run with both full ionic charges and employing the electronic continuum correction (implemented through charge scaling) to account effectively for electronic polarisation. The experimental data were then used to assess the successes and shortcomings of the investigated force-fields. We found that due to the very good signal-to-noise ratio in the experimental data, they provide a very narrow window for the position of the first hydration shell of the chloride ion. This allowed us to establish the importance of effectively accounting for electronic polarisation, as well as adjusting the ionic size, for obtaining a force-field which compares quantitatively to the experimental data. The present results emphasise the utility of performing neutron diffraction with isotopic substitution as a powerful tool in gaining insight and examining the validity of force-fields in concentrated electrolyte solutions.  相似文献   

14.
Thorium-to-uranium ratios have been determined in different soil samples using CR-39 and LR-115-II solid-state nuclear track detectors (SSNTDs). A calibration method based on determination of SSNTD registration sensitivity ratio for α-particles of thorium and uranium series has been developed. Thorium and uranium contents of the standard soil samples have been determined and compared with its known values. There is a good agreement between the results of this method and the values of standard samples. The method is simple, inexpensive, non-destructive and has a wide range of applications in environment, building materials and petroleum fields.  相似文献   

15.
三种浙产特色药材炮制前后微量元素与重金属的含量研究   总被引:1,自引:0,他引:1  
用微波消解-电感耦合等离子体质谱法(ICP-MS)同时测定了3种浙产特色药材炮制前后Mn, Fe, Cu, Zn, Cr, As, Cd, Pb的含量。该方法的加样回收率在95.2%~106.3%之间,相对标准偏差RSD在0.69%~2.34%之间。试验结果显示,3种药材炮制前后对人体有益的微量元素Mn, Fe, Zn的含量均较高;而有害重金属元素Cu, Cd, Cr, Pb, As的含量均低于《中国药典》的限量标准,炮制加工均使其中的微量元素及重金属含量有所变化,不同的炮制方法在个别元素含量上存在差异。炮制后除Pb的含量明显下降,Cu, As, Cd基本不变外,其他元素的含量均有不同程度的增加,这种差异可能与药材的炮制方法有关。该测定结果为进一步探讨3种浙产特色药材的炮制方法与其功效的相关性提供了科学依据。  相似文献   

16.
ICP-OES和ICP-MS测定中日两国大米中27种矿质元素含量   总被引:6,自引:0,他引:6  
收集了16种中国大米和11种日本大米,经过微波消解或干灰化法处理后,采用电感耦合等离子体发射光谱法(ICP-OES)和电感耦合等离子体质谱法(ICP-MS)测定了其中Al,As,B,Ba,Ca,Cd,Co,Cr,Cs,Cu,Fe,Hg,K,Mg,Mn,Mo,Na,Ni,P,Pb,Rb,S,Se,Sr,Tl,V和Zn等27种矿质元素的含量,并用生物标准参考物质大米(GBW10010)评价了分析方法的准确度。研究结果表明,基于碰撞反应池技术(CCT)的ICP-MS能有效降低一些多原子离子对低m/z元素离子计数的干扰;与日本大米相比,中国大米中Al,S,Sr等元素含量显著偏高,而B,Cd,Cs,Mg,Mo,P,Pb,Zn等元素含量显著偏低(P0.05),采用聚类分析(最小方差法)对矿质元素含量进行处理,可正确判别两国大米。另外,还发现大米中Mg和P含量之间存在很强的线性相关性,相关系数高达0.9552。  相似文献   

17.
Polarization energy dispersive X‐ray fluorescence spectrometry was used in the determination of Pb, As and Cd, as well as Cr, Cu, Zn, Ni and other minor and trace elements in the soil samples taken from a polluted area by lead mine exploitation. Two difficulties have to be overcome. One is strong overlap of Pb Lα over As Kα and another is lack of suitable certified reference materials. The different excitation conditions and analytical lines were tried to reduce the impact of overlap of Pb Lα over As Kα. When KBr was used as the second target, compared with Zr, the proportion from Pb Lα was reduced about six times. Even so, however, the overlap was not reduced enough to be ignored. The inductively coupled plasma atomic emission spectrometry and mass spectrometry methods were used to analyze parts of soil samples and provide data for compensating lack of reference materials. By this method, the analytical concentration range of Pb, As and Cd were significantly extended. The analytical range of Pb, As and Cd were 1.4 µg/g~4.2%, 0.6 µg/g~9.3% and 0.5 µg/g~1500 µg/g, respectively. The high concentrations of Pb, As and Cd were found in the samples in the vicinity of the Pb‐Zn mine. The concentrations of Pb, As, Cd, Zn and Cu were higher than the Class III in the Chinese environmental quality standard for soils. The highest concentrations of Pb, As, Cd and Zn in the soil samples were 14 960, 2726, 65 and 9439 µg/g, respectively. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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