铀矿坑水样中铀电沉积层的表征

描述了硫酸铵溶液中铀矿坑水样品中铀的电沉积层特性。 电沉积液为10 ml 0.8 M的硫酸铵溶液, 电流密度0.6 A/cm2, pH值为2.5, 电镀1 h。 电沉积经化学分离后的水样品和电沉积的纯硝酸铀酰样品进行了比较, 并对二者分别做了红外(IR)光谱、 扫描电镜(SEM)、 元素分析以及α能谱测量。 IR谱上铀酰离子的反对称伸缩振动峰在887 cm-1附近, 使电沉积在不锈钢片上的铀主要以铀酰离子水合物的形式存在, 有一部分NH+4以NH3的形式替代水合物中的水, 使电沉积层中铀的化合物形式为UO2(OH)2·xNH3·yH2O或者UO2(OH)2-x·(ONH4)x·yH2O, 铀酰离子通过链的形式形成聚合结构。 SEM照片显示电沉积层均匀, 没堆积成团现象出现。 α谱表明电沉积层中铀的同位素主要是238U和234U, 相应的α能量峰4198和4773 keV很显著, 没其它峰的干扰。 Characteristics of electrodeposited uranium films of uranium ore water sample in ammonium sulphate was investigated in this work. The optimized electrodeposited conditions were as follows: electrolyte was ammonium sulphate of 0.8 M, and current density at the cathode was 0.6 A/cm2, electrolyte pH value was 2.5, the time of plating on the electrodeposition was 1 h. In this situation, the uniform, thin and adheresive films were produced by electrodeposition method. Two samples were made, one electrodeposition of pure uranyl nitrate, and another electrodeposition of uranium ore water sample after chemical separation. Characteristics of electrodeposited uranium films of uranium ore water sample after chemical separation was studied, making comparisons with electrodeposited films of uranyl nitrate. The analysis of film characteristics was done through infrared (IR) spectrum, scanning electron microscopy(SEM), element analysis and α spectrum measurment. According to Fourier transform infrared spectra, the asymmetric stretching vibration band of uranyl group is around 887 cm-1. In addition, according to IR spectrum, we know that uranium exists mainly as the form of hydrated polymeric compound in the film. Electrodeposited uranium films also included many NH+4. Polymeric structures of variable composition were present in the electrodeposited samples, with the unit monomeric formula UO2(OH)2·xNH3·yH2O or UO2(OH)2-x·(ONH4)x·yH2O. Scanning electron microscopy shows that the two samples have similar surface characteristics and no cluster is observed. The samples were also measured by spectrometer equipped with Passivated Implanted Planar Silicon(PIPS) detector. From the α spectrum, we know that isotopes of uranium in the film are 238U and 234U. 235U is not found in the α spectrum. It also shows that the chemical separation process can isolate uranium from other interfering elements effectively, the result of chemical separation is very satisfactory and electrodeposited process is rather efficient. Source electrodeposited in ammonium sulphate through optimized conditions satisfies the need of high resolution α spectrum.     

Design of multi-spectrum BRDF measurement system

A multi-spectrum bidirectional reflectance distribution function (BRDF) measurement system was developed with the adoption of single reference standard measurement method. An arm-adjustable corner device was designed for the BRDF system. Changing the distance to the sample by moving the detector arm made the device applicable to different wavelengths. The system could be used for the spectrum range from visible light (0.6328μm) to mid-far infrared (10.6μm), the facular size between 0.8-3 cm. The rotating limit of detector arm was±180°, the rotation range of sample holding table was 360°, and the angle resolution was 0.036°. A silicon carbide sample was measured using this system with reflectance zenith from -55°to 55°. According to the error analysis, the measurement uncertainty of this device was about 6.42%.     

铀氧化物中238U含量的定量研究

准确定量铀氧化物样品中238U的含量对于裂变产额测量等工作具有重要意义,其定量方法的研究对于涉及238U的绝对测量的诸多实验都具有参考价值。利用四川大学2.5 MeV质子静电加速器产生的准单能中子对八氧化三铀样品进行中子活化,用高纯锗探测器测量活化产物的β衰变子体239Np的277.6 keV特征γ射线,利用已知的活化截面,算出样品中238U的质量占比为79.1%,不确定度为6.2%。利用电感耦合等离子体质谱法对样品中238U的含量进行了测量,其质量占比为59.2%。此外,基于EA3000元素分析仪、卡尔费休电位滴定仪和TGA-DSC2同步热分析质谱联用仪,测知样品中不含N元素,含水量在2.2%以下。并利用PIXE方法排除了样品中含有Al元素以上杂质,利用EPBS方法测知样品中U/O原子数比为1:3.6,误差约2%,推知样品中238U质量占比为80%,验证了活化法测得的238U含量。最终测得样品中238U的质量占比为79.1%,不确定度6.2%。对照按U3O8分子式折算的84.5%,考虑到水分含量等,此结果合理。The accurate quantification of 238U in uranium oxides is of great importance for measurements of fission yield. The study for the method of 238U quantification has significance to lots of experiments involving absolute measurement of 238U. The reaction (n, γ) in the triuranium octoxide samples was induced by T(p,n)3He quasi-monoenergetic neutrons provided by the 2.5 MeV proton electrostatic accelerator in Sichuan University. The 277.6 keV characteristic γ ray of 239Np that comes from β-decay of the activation product 239U was detected by a HPGe detector. With the known (n, γ) cross section, the mass percentage of 238U in samples was determined to be 79.1%, with the uncertainty of 6.2%. ICP-MS was also used in the quantification of 238U in samples, its result was 59.2%. Meanwhile, the samples were analyzed by other several methods and the results showed that less than 2.2% H₂O, no nitrogen, and no other impurity elements above Al were contained in the samples. EPBS was used to measure the atomic ratio of U and O and it was found that the mass percentage of 238U in samples was about 80%, verifying the result 79.1% of INAA.     

Growth and Characterization of a Kind of Nitrogen-Rich Niobium Nitride for Bolometer Applications at Terahertz Frequencies

Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2 μm × 2 μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb^3＋ and Nb^5＋, or Nb^4＋.     

Effects of rapid thermal annealing on the room-temperature NO2-sensing properties of WO3 thin films under LED radiation

WO3 thin films were sputtered onto alumina substrates by DC facing-target magnetron sputtering.One sample was rapid-thermal-annealed(RTA) at 600℃ in a gas mixture of N2:O2=4:1,and as a comparison,another was conventionally thermal-annealed at 600℃ in air.The morphology of both was investigated by scanning electron microscopy(SEM) and atomic force microscopy(AFM),and the crystallization structure and phase identification were characterized by X-ray diffraction(XRD).The NO2-sensing measurements were taken under LED light at room temperature.The sensitivity of the RTA-treated sample was found to be high,up to nearly 100,whereas the sensitivity of the conventionally thermal-annealed sample was about five under the same conditions.From the much better selectivity and response-recovery characteristics,it can be concluded that compared to conventional thermal annealing,RTA has a greater effect on the NO2-sensing properties of WO3 thin films.     

2.8MeV中子诱发238U裂变的瞬发中子谱高能段实验测量

在中国原子能科学研究院的高压倍加器上利用中子飞行时间方法测量了2.8 MeV中子引起238U裂变的瞬发中子能谱,通过增大样品量和设计合适的屏蔽体提高了效应/本底比,使得测量数据的不确定度满足预期目标（在5.5～14 MeV能区内,能量间隔为0.5 MeV条件下能谱的不确定度小于10%）。将实验几何、中子源能量分布及角分布、探测效率、束流的时间结构等实验条件输入到MCNP程序里,模拟了出射的中子谱,模拟结果与测量结果在不确定度范围内一致,验证了在入射中子能量较低时238>U的裂变瞬发中子谱评价数据的可靠性。The Prompt Fission Neutron Spectrum (PFNS) of 238U induced by 2.8 MeV neutron was measured using the Cockcroft-Walton accelerator in China Institute of Atomic Energy (CIAE). The signal/background ratio was improved by increasing the amount of sample mass and using an appropriate shielding system. The final uncertainty of neutron energy spectrum in 5.5～14 MeV region is less than 10% with a bin size of 0.5 MeV which has reached this project's anticipation. The experimental geometry, the angular distribution and energy distribution of neutron source, the detection efficiency and time structure of deuteron beam were inputted into the MCNP code to simulate the outgoing neutron spectrum. The simulated results agree with the experimental ones within the uncertainty. The result indicates that the evaluated PFNS for 238U at low neutron energy is reliable.     

Synthesis of N-type semiconductor diamonds with sulfur,boron co-doping in FeNiMnCo-C system at high pressure and high temperature

A series of diamonds with boron and sulfur co-doping were synthesized in the Fe Ni Mn Co-C system by temperature gradient growth(TGG) under high pressure and high temperature(HPHT). Because of differences in additives, the resulting diamond crystals were colorless, blue-black, or yellow. Their morphologies were slab, tower, or minaret-like. Analysis of the x-ray photoelectron spectra(XPS) of these diamonds shows the presence of B, S, and N in samples from which N was not eliminated. But only the B dopant was assuredly incorporated in the samples from which N was eliminated. Resistivity and Hall mobility were 8.510 ?·cm and 760.870 cm~2/V·s, respectively, for a P-type diamond sample from which nitrogen was eliminated. Correspondingly, resistivity and Hall mobility were 4.211×10~5 ?·cm and 76.300 cm~2/V·s for an N-type diamond sample from which nitrogen was not eliminated. Large N-type diamonds of type Ib with B–S doping were acquired.     

The effects of Zn vacancies on ferromagnetism in Cu-doped ZnO films controlled by oxygen pressure and Li doping

Zn0.99Cu0.01O films were studied experimentally and theoretically.The films were prepared by pulsed-laser deposi tion on Pt(111)/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromag netic properties.The structural,magnetic,and optical properties were studied,and it was found that all the samples possess a typical wurtzite structure,and that the films exhibit room-temperature ferromagnetism.The sample deposited at 600℃and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83μB/Cu.The enhanced ferromagnetism in the(Cu,Li)-codoped ZnO is attributable to the existence of Zn vacancies(VZn),as shown by first-principles calcu lations.The photoluminescence analysis demonstrated the existence of V Zn in both Zn0.99Cu0.01O and(Cu,Li)-codoped ZnO thin films,and this plays an important role in the increase of ferromagnetism,according to the results of first-principles calculations.     

Measurements of effective delayed neutron fraction in a fast neutron reactor using the perturbation method

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.     

Perpendicular magnetic anisotropy of Pd/Co2MnSi/NiFe2O4/Pd multilayers on F-mica substrates

Pd/Co₂MnSi(CMS)/NiFe₂O₄(NFO)/Pd multilayers were fabricated on F-mica substrate by magnetron sputtering.The best PMA performance of the multilayer structure Pd(3 nm)/CMS(5 nm)/NFO(0.8 nm)/Pd(3 nm)was obtained by adjusting the thickness of the CMS and NFO layers.F-mica substrate has a flatter surface than glass and Si/SiO₂ substrate.The magnetic anisotropy energy density(K_eff)of the sample deposited on F-mica substrates is 0.6711 Merg/cm³(1 erg=10^-7 J),which is about 30%higher than that of the multilayer films deposited on glass(0.475 Merg/cm³)and Si/SiO₂(0.511 Merg/cm³)substrates,and the R_Hall and H_C are also significantly increased.In this study,the NFO layer prepared by sputtering in the high purity Ar environment was exposed to the high purity O₂ atmosphere for 5 min,which can effectively eliminate the oxygen loss and oxygen vacancy in NFO,ensuring enough Co-O orbital hybridization at the interface of CMS/NFO,and thus effectively improve the sample PMA.     

Background structure in the Heidelberg-Moscow experiment on the search and investigation of double beta decay of 76Ge1

Independent analysis of the spectra from the Heidelberg-Moscow experiment has been carried out. A direct comparison of the peak intensities in the spectra allows for the conclusion that in the energy range up to 3200 keV the background is due to the detection of γ rays from the decay of trace impurities of anthropogenic and cosmogenic nuclides occurring in the apparatus between the HPGe detectors and the main (Pb and Cu) shielding. The ²²⁶Ra, ²¹⁴Pb, and ²¹⁴Bi γ rays observed in the spectra are shown to arise in the ²²⁶Ra rather than ²³⁸U decay chain. The estimates of the expected intensities of the weak ²¹⁴Bi γ rays in the spectrum region around Q _ββ(⁷⁶Ge) = 2039 keV do not contradict the observation of the peak at 2039 keV as claimed by Klapdor-Kleingrothaus and coauthors. The text was submitted by the authors in English.     

Dose assessment of bremsstrahlung induced by beta-emitting radioisotopes of uranium-238 series and lead in human tissues

In the natural uranium-238 decay series, pure beta isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb and ²¹⁰Bi are released. The few lead isotopes such as ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb are good beta emitters. In certain nuclear reactions of reactor these isotopes are released. These beta isotopes have maximum beta energies, which induce the bremsstrahlung radiation. The bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. The shapes of bremsstrahlung spectra are a basic ingredient in the understanding and quantification of beta-ray dosimetry. The bremsstrahlung spectra produced by these high-energy isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ²¹⁰Bi, ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb in bone, muscle and teeth are studied, and the computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth–dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The evaluated beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The efficiency, intensity and dose rate of bremsstrahlung induced by beta isotopes of natural uranium-238 decay series and beta-emitting lead isotopes in human tissues such as brain, breast, heart, kidney, liver, muscle, pancreas and bone have also been studied in the present investigation. The values of bremsstrahlung dosimetric parameters are low for pancreas, but they are high for bone. For all studied tissues these parameters are high for ²³⁴Pa, but low for ²¹⁰Pb.     

GaP:(Bi,N)晶体中束缚激子的辐射复合及能量转移

本文研究了在4.2K—147K温度范围内GaP:(Bi,N)晶体的光致发光光谱的精细结构,积分强度及其随温度的变化,并将它们与GaP:Bi,GaP:N光谱进行比较。首次发现在GaP:(Bi,N)晶体中激发能量从孤立N中心和NNi对(i≥3)中心到Bi中心的转移,增大了Bi束缚激子态的浓度,使Bi发射带增强。     

Radioactivity concentration measurement and analysis in construction floor materials of Korea

In this study, the radioactive concentrations contained in samples of commonly used building floor materials were measured. This result can be used as basic information for public health and the environment. Among building floor materials, samples of induction blocks, cement bricks, artificial granite blocks and compact high-pressure blocks were chosen and used. A detailed gamma nuclide analysis was performed with a multichannel analyzer by putting these samples on a high-purity germanium detector which is a semiconductor detector. In order to measure the concentration of radionuclides, a spectrum file was obtained by analyzing the concentration of gamma radionuclides and setting the measurement time as 1000, 4000, 7000 and 10,000?s. According to the study results, K-40, Bi-214, Pb-214, Ra-226 and U-235 were detected in the induction blocks measured at 10,000?s and K-40, Th-230, Bi-214, Pb-214, Ra-226 and Na-22 were detected in the cement bricks measured at 10,000?s. K-40, Bi-214, Pb-214, Th-234, U-235 and Ra-223 were detected in the artificial granite blocks measured at 10,000?s and K-40, Bi-214, Pb-214, Th-234, Ra-226, Ra-223 and Mn-54 were detected in the compact high-pressure blocks. In conclusion, low-level radioactivity was detected in building floor materials, so it is thought that measures to reduce radioactivity and further studies on this will be needed.     

Mapping the inhomogeneity of the U and Th distributions — using sample size concept in the field conditions

Indigenously fabricated portable gamma-ray spectrometer (PGRS) is used for the measurement of gamma activity of ²¹⁴Bi (1.76 MeV) and ²⁰⁸TI (2.62 MeV), under field conditions in Mohar area, Shivpuri Distt. (MP). The energies are discriminated by using a Nal (TI) crystal of size 1.75″ × 2″. PGRS used to map the primordial elemental distributions shows reversals of concentration of thorium and uranium (represented by radium group) in field and lab analysis in many samples, which is attributed to the inhomogenity of distribution of these elements in the area. The concept of difference in the volume of dish shaped field sample and the randomly picked up sample from the field grid point (400 gm in lab analysis) is utilized to interpret the inhomogenity of these elements. However interpretations are based on the assumption that these primordial elements (U, Th) are in secular equilibrium and the terrain has low topographic relief.      

Bi-induced vibrational modes in GaAsBi

We have studied GaAs_1−xBi_x (up to x3%) using Raman scattering with two different polarization configurations. Two Bi-induced phonon modes are observed at 186 cm⁻¹ and 214 cm⁻¹ with increasing Raman intensity as the Bi concentration increases. By comparing Raman selection rules for the observed Bi-induced phonon modes with those for the substitutional N vibrational mode (GaN mode) in GaAsN, the phonon mode at 214 cm⁻¹ is identified as originating from substitutional Bi at the As site in GaAsBi.     

Radon loss from encapsulated sediments in Ge gamma-ray spectrometry for the annual radiation dose determination in luminescence dating

In Ge gamma-ray spectrometry for the annual radiation dose determination in the luminescence dating of sediments, the picture of ²²⁶Ra enrichment or depletion (in the ²³⁸U decay series) obtained via measurement of its ²¹⁴Pb and ²¹⁴Bi daughters may be disturbed by the ²²²Rn-content of the sample being decreased due to manipulations such as drying and pulverizing. Therefore, it is common practice to start the measurement only about 1 month after encapsulating the material, after which the ²²⁶Ra(1600 a)- ²²²Rn(3.82 d) mother-daughter equilibrium is re-established. Evidently, this only holds on condition that no significant escape of Rn occurs out of the sediment after making it up for counting. In order to experimentally investigate this effect, in the present work measurements were carried out with various types of dried and pulverized sediments that were either encapsulated in screw-cap polystyrene vials or in sealed glass containers, or that were mixed with molten wax followed by solidification in a cylindrical geometry. From the results obtained, it could be concluded that preparation and counting of the sediment-wax mixture is the method of choice.     

用不同强度皮秒脉冲相关技术测量甲酚紫吸收恢复时间

以Ar+离子锁模激光器同步泵浦R6G染料激光器作光源,用不同强度皮秒脉冲相关的泵涌—探测技术测得甲酚紫甲醇溶液的吸收恢复时间为162±3.5ps.并且用三能级模型对这一动力学过程进行了理论分析.     

Large enhancement of Faraday rotation by localized surface plasmon resonance in Au nanoparticles embedded in Bi:YIG film

A large enhancement of the Faraday rotation, which is associated with localized surface plasmon resonance (LSPR), was obtained in a sample with Au nanoparticles embedded in a Bi-substituted yttrium iron garnet (Bi:YIG) film. On a quartz substrate, Au nanoparticles were formed by heating an Au thin film, and a Bi:YIG film was then deposited on them. A sample containing the Au nanoparticles produced by 1000 °C heating showed a resonant attenuation with narrower bandwidth in the transmission spectrum than nanoparticles of other samples formed by low-temperature heating. The sharp resonant Faraday rotation angle was 4.4 times larger than the estimated intrinsic Bi:YIG film at the LSPR wavelength; the angular difference was 0.14°. A discrepancy in the bandwidth between the transmission attenuation and the resonant Faraday rotation is discussed.