Analysis of Uranium Enrichment in Environment Samples Using HPGe γ-ray Spectrometry

In this work a method for determination of uranium enrichment in environmental samples was studied and the minimum detectable activities of 235U in environmental samples (including soil, water, swipe)     

Synthesis of TBP-coated magnetic Pst-DVB particles for uranium separation

Magnetically assisted chemical separation process is an efficient method used widely in separating radionu- clides and heavy metals in environmental samples. It is simple, compact and cost-effective, with less sec- ondary waste streams. Tributyl phosphate （TBP）-coated magnetic poly （styrene-divinylbenzene） （Pst-DVB） nano-particles were synthesized and characterized by transmission electron microscopy, scanning electron mi- croscopy, vibrating sample magnetometer, thermogravimetry and Fourier transform infrared spectrometry. The application of TBP-coated magnetic Pst-DVB particles in separating low concentration of uranium from aque- ous media was evaluated, and the equilibrium adsorption isotherm was investigated. Our results indicate that the TBP-coated magnetic Pst-DVB particles may be of potential application for uranium separation.     

Measurement of the natural ^36Cl and ^236U in uranium mineral with accelerator mass spectrometry

The concentration of the natural ultra-trace radionuclides CI and U in the uranium depended on the neutron flux.In this article,a method for measuring ³⁶C1 and ²³⁶U in the same uranium mineral with accelerator mass spectrometry was developed in China Institute of Atomic Energy,providing a protocol of the potential application of ²³⁶U in uranium mining,environmental,and geological research.The two samples were from Guangxi and Shanxi province,China,and their ratios ³⁶Cl/C1 and ²³⁶U/²³⁸U were measured.More experimental data conduced to understand the natural nuclides in the uranium mineral.We plan to conduct more efforts on the research.     

Nuclear Safeguards Techniques Non-destructive Assaying for Attributes of Fast Neutron Reactor＇s Fresh Fuel

We have adopted active neutron coincidence method and y-ray measurement method in order to measure the attributes of fast neutron reactor＇s fresh fuel. An improved uranium neutron coincidence collar （UNCC） was used for measuring the ^235U enrichment distribution of the 2 pieces fuel assembles. The measured results show curve＇s trend is the same as the fact of distribution. Fig. 1 shows the assembly＇s neutron coincidence counting rate.     

CHEMICAL SPECIES OF IRIDIUM AND OTHER TRACE ELEMENTS IN THE CRETACEOUS-TERTIARY BOUNDARY CLAYS AND ITS IMPLICATION

The geological samples: Cretaceous- Tertiary (K- T) boundary clays, meteorites, volcanic lava, and ultrabasic rock were separated into carbonate, metal, sulfide, oxide, silicate and acid- resistant residue by a selective chemical dissolution procedure developed in our laboratory. Some conclusions were drawn by analyzing the chemical speciation of anomalous iridium in the above samples and especially by studying the characteristics of mineral components in those residue phases. (1) It is impossible that the anomalous Ir was caused by geochemical enrichment; (2) The iridium enrichment in the K- T boundaries did not necessarily associate with kerogen; (3) The volcano activity has participated in the extinction event at the end of Cretaceous; (4) Extraterrestrial impact was the trigger of K- T event. Then, we proposed a mixed model by which the extant anomalous Ir in K- T boundary clays was interpreted as a combined effect of extraterrestrial impact, volcano eruption and post- depositional redistribution.     

Preparation of ^151Sm Standards for AMS Measurement

^151Sm （T1/2=90 a） is a kind of long-lived fission products. It was applied to the industry, agriculture, national defence and many other fields. The measurement of ^151Sm is very significant in environment science, and life science, etc. The content of Sm in samples is very low especially in biological samples （10^-6-10 ^-9）, so AMS is the best choice for the measurement of Sm with high sensitivity. But AMS is a kind of relative measurement method which needs standards to calibrate. The preparation of ^151Sm standards is described in this paper.     

DBC solvent extraction of U(VI) from thiocyanate medium

1 INTRODUCTIONFOr many years much effort has been invested in studying the solvent extraction ofactfordes, such as thoriuxn, neptunium, americium, and uranium with crown eth..,.ll'ZJAmong those papers on extraction of uranium with crown ethers, most experbontswere performed in HCI or HNO3 .edi..[1-9] It was considered that the urhaum(VI)was extracted as a form of complex aulon UO,CI.' in HCI and chlorides media.[4'9]Even thiocyanate is somewhat similar to halogen in chemical proper…     

Analytic fitting and simulation methods for characteristic X-ray peaks from Si-PIN detector

A semi-empirical detector response function （DRF） model is established to fit characteristic X-ray peaks recorded in Si-PIN spectra, which is mainly composed of four components： a truncated step function, a Gaussian-shaped full-energy peak, a Gaussian-shaped Si escape peak and an exponential tail. A simple but useful statistical distribution-based analytic method （SDA） is proposed to achieve accurate values of standard deviation for characteristic X-ray peaks. And the values of the model parameters except for the standard deviation are obtained by weighted least-squares fitting of the pulse-height spectra from a number of pure-element samples. A Monte Carlo model is also established to simulate the X-ray measurement setup. The simulated flux spectrum can be transformed by Si-PIN detector response function to real pulse height spectrum as studied in this work. Finally, the fitting result for a copper alloy sample was compared with experimental spectra, and the validity of the present method was demonstrated.     

Determination of boron concentration in uranium fuel samples by ICP-OES following a separation step by cation exchange resin

The boron content of uranium fuel samples with boron concentrations in the range of 0.05–10 μg/g was determined using inductively coupled plasma optical emission spectrometry(ICP-OES) after the uranium was separated by cation exchange. The samples were dissolved in 3 M HNO_3 on a hot plate at 150℃ and evaporated to near dryness. The residues were redissolved in 0.2 M HNO-_3 and passed through a column loaded with Dowex 50WX8-400 resin. Uranium was adsorbed on the resin,while boron was easily eluted with 0.2 M HNO_3. The boron content of the effluent was determined using ICPOES. Several strategies were employed to improve the reliability of the experimentally determined boron content.The addition of mannitol and proper control of the evaporation process were shown to be effective in preventing boron loss during sample dissolution and evaporation. The memory effect was eliminated by flushing the system with 1.5% ammonia for 30 s between successive sample runs,and the matrix match method was used to eliminate the matrix effect arising from mannitol during the ICP-OES analysis. The accuracy of the results of the analysis was determined by addition recovery tests and by comparison with the results of three Chinese certified reference materials(GBW04242, GBW04243, and GBW04232). Using the method we developed, the limit of detection for boron was as low as 0.05 μg/g in uranium fuel samples, and the relative standard deviations for 0.1–0.5 g uranium samples with 0.05–2 μg/g of boron were within 9%.     

ELECTRON SPIN RESONANCE DATING FOR THE AGE OF PEKING-MAN, LOC.1, ZHOUKOUDIAN, BEIJING

In this paper, we used ESR dating method to measure the accumulative dose of the fossil teeth samples, which are contemporaneous with the Peking-Man. The internal annual dose rate of samples are got by neutron activation analysis and the environmental annual dose rate by highly sensitive TL dosimeters to be embedded in cave deposits in the site. The results of ESR dating are corresponded with the dating results obtained by U-series, FT, TL and paleomagnetic stratigraphical methods on the 3rd, 4th, 7th and 10th layers. Calculation of using different models, the close-equilibrium model, the linear uranium accumulation model and radon loss-linear uranium accumulation model, for travertine, deer teeth and rhinoceros tooth, we obtained the age of the First Peking- Man in the nth layer is 578 ka and gave ages of other layers, from the 1st to the 13th layer in Peking- Man site.     

Development of Vehicle Security Portal for Special Nuclear Material and Other Radionuclides

After indoor debugging the vehicle portal special nuclear material monitor was mounted at the outdoor scene in 2005. The tests of detection sensitivity of the monitor for high enrichment uranium（HEU） and low-burnup plutonium with different type of vehicles have been performed. The tests of statistical false alarm rate and stability of the monitor have been performed too.     

High-Density Polyethylene(HDPE) Surface Treatment Using an RF Capacitive Atmospheric Pressure Cold Ar Plasma Jet

In this study,a high-density polyethylene（HDPE,5-mm-thick,0.95 g/cm3） surface was treated using an RF capacitive atmospheric pressure cold Ar plasma jet.By using this Ar plasma jet,a hydrophilic HDPE surface was formed during the plasma treatment.In particular, the effects of an additive gas（N₂ or O2） on the HDPE surface treatment were investigated in detail.It was shown that the addition of N2 or O2 gas had an important influence on the HDPE surface treatment.Compared to pure Ar plasma treatment,a lower value of water contact angle （WCA） was obtained when a trace of N2 or O2 gas was added.It was also found that besides the quantities of active species in the plasma jet,the treatment temperature played an important role in the HDPE surface treatment.This is because surface molecular motion is not negligible when the treatment temperature is close to the melting point of the polymer.     

Study on Analysis of Isotopic Ratio of Uranium in Uranium-Bearing Particle by FT-TIMS

Environmental sampling is an important technique for international nuclear sateguaras, The isotopic compositions of uranium-bearing particles must be analyzed in uranium enrichment facility for safeguards Many techniques were used in analysis of uranium containing particles, and FT-TIMS （fission track- thermal ionization mass spectrometry） is one of them.     

Interaction between uranium and humic acid （Ⅰ）： Adsorption behaviors of U（Ⅵ） in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) >SHA (HA from the surface) >THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was achieved at a suitable uranium concentration (10 mg·L-1 U(Ⅵ) for SHA and THA, 20 mg·L-1 U(Ⅵ) for FHA), the adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g) ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5-6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

Study of some marine bivalves as the biomonitor candidates for environmental assessment of the Jianzhou Bay by NAA and AAS

Some kinds of marine bivalves were selected as the biomonitor candidates to study the possibility of the environmentalassessmentof the jiaozhou Bay with biomonitors.The contents of 29 elements in bivalve samples were determined by neutron activation analysis and atomic absorption spectrometry.It is found that clam is a suitable kind of marine bivalves as a biomonitor to evaluate the environmental quality of the Jiaozhou Bay.the environmental status of some sampling sites in this marine area wastentatively assessed by the biomonitors of calm and mussel.     

Synthesis of Novel Chelating Agents for Actinide Ions

The synthesis of novel chelating agents for actinide ions is very important to the therapy of internal pollution of uranium and plutonium. This report describes the reactions between 1, 3, 5-benzenetricar- bonyl trichloride and desferrioxamine B （DFO） in aqueous solution. Firstly, DFO was protected as FeDFO, then, 1, 3, 5-benzenetricarbonyl trichloride was mixed with FeDFO in the ratio of 1 ： 3.     

IRIS reactor core with thorium fuel

This work is aimed at running the first IRIS reactor core with mixed thorium dioxide fuel（ThO₂-UO₂ and ThO₂-PuO₂）.Calculations are performed by using Dragon 4.0.4 and Citation codes.The results show the multiplication factor(K_eff) for central and peripheral assemblies as a function of burnup.To ensure the proliferation resistance,the value of ²³⁵U enrichment is < 20%.The K_eff is calculated using Dragon 4.0.4 for a single fuel rod and the model developed to fuel assembly,while the whole core was calculated using Citation code.For a fuel burnup,the use of increased enrichment fuel in the IRIS core leads to high reserve of reactivity,which is compensated with an integral fuel burnable absorber.The self-shielding of boron is in an IRIS reactor fuel.The effect of increased enrichment to the burn-up rates,and burnable poison distribution on the reactor performance,are evaluated.The equipment used in traditional light water reactors is evaluated for designing a small unit IRIS reactor.     

Study of Metal and Ceramic Thermionic Vacuum arc Discharges

The thermionic vacuum arc （TVA） is a new type of plasma source, which generates a pure metal and ceramic vapour plasma containing ions with a directed energy. TVA discharges can be ignited in high vacuum conditions between a heated cathode （electron gun） and an anode （tungsten crucible） containing the material. The accelerated electron beam, incident on the anode, heats the crucible, together with its contents, to a high temperature. After establishing a steadystate density of the evaporating anode material atoms, and when the voltage applied is high enough, a bright discharge is ignited between the electrodes. We generated silver and Al2O3 TVA discharges in order to compare the metal and ceramic TVA discharges. The electrical and optical characteristics of silver and Al2O3 TVA discharges were analysed. The TVA is also a new technique for the deposition of thin films. The film condenses on the sample from the plasma state of the vapour phase of the anode material, generated by a TVA. We deposited silver and Al2O3 thin films onto an aluminium substrate layer-by-layer using their TVA discharges, and produced micro and/or nano-layer Ag-Al2O3 composite samples. The composite samples using scanning electron microscopy was also analysed.     

Development of Vehicle Security Portal for Special Nuclear Material and Other Radionuclides

After indoor debugging the vehicle portal special nuclear material monitor was mounted at the outdoor scene in 2005. The tests of detection sensitivity of the monitor for high enrichment uranium(HEU) and low-burnup plutonium with different type of vehicle…     

Remote open-path laser-induced breakdown spectroscopy for the analysis of manganese in steel samples at high temperature

A remote open-path laser-induced breakdown spectroscopy(LIBS) system was designed and studied in the present work for the purpose of combining the LIBS technique with the steel production line. In this system, the relatively simple configuration and optics were employed to measure the steel samples at a remote distance and a hot sample temperature. The system has obtained a robustness for the deviation of the sample position because of the open-path and alloptical structure. The measurement was carried out at different sample temperatures by placing the samples in a muffle furnace with a window in the front door. The results show that the intensity of the spectral lines increased as the sample temperature increased. The influence of the sample temperature on the quantitative analysis of manganese in the steel samples was investigated by measuring ten standard steel samples at different temperatures. Three samples were selected as the test sample for the simulation measurement. The results show that, at the sample temperature of 500 ℃, the average relative error of prediction is 3.1% and the average relative standard deviation is 7.7%, respectively.