Removal of radionuclide Sr2+ ions from aqueous solution using synthesized magnetic chitosan beads

Strontium-90 is one of the main fission products, existing in the radioactive wastes produced in nuclear power plant. In this paper, a novel magnetic chitosan beads were synthesized, characterized and applied for removal of Sr²⁺ ions from aqueous solution. The SEM analysis indicated that the magnetic beads were in regular spherical geometry with about 1 mm diameter. The XRD and EDS analysis revealed that the chitosan beads were magnetic and can be used for the magnetic separation. The influencing factors of Sr²⁺ sorption onto magnetic chitosan beads were studied, including contact time, initial pH value, initial Sr²⁺concentration and sorbent dosage. The maximum adsorption capacity (q_m) of Sr²⁺ was calculated to be 11.58 mg/g using the Langmuir isotherm. The kinetic data were analyzed by intra particle diffusion model. The FT-IR study revealed that –NH₂ was mainly involved in Sr²⁺ sorption by magnetic chitosan beads.     

Improving the properties of poly(ethylene-co-vinyl acetate)/clay composite by using electron beam irradiation

Effect of electron beam irradiation on the thermal and mechanical properties of poly(ethylene-co-vinyl acetate) (EVA)/clay composites prepared by blending using solvent method has been investigated. The results show that the tensile strength increased continuously with increasing electron beam (EB) irradiation dose up to 200 kGy, thereafter decreased with further increase in dose, similarly increased with increasing the clay percentage until 50%, then decreases with further increase in clay percentage. Alternatively, elongation at break decreased continuously with increasing irradiation dose and clay percentage in the prepared composite. Conversely hardness increased continuously with increasing both clay percentage and irradiation doses. The thermogravimetric analysis revealed that thermal stability of the EVA/clay composites improved with increasing dose. The improvement in the mechanical and thermal properties is attributed to the formation of radiation-induced crosslinking as evidenced by the gel-content results. The adsorption capacity of EVA/clay composite for acid red 37 dye was 63.6 (mg/g) at adsorption conditions of: EVA/clay 50:50 (wt.%); dye concentration: 300 mg/l; sample dose: 0.05 g/25.00 ml; initial pH 7.0; temperature: 30 °C and equilibrium time: 8 h.     

Removal of Co2+ from radioactive wastewater by polyvinyl alcohol (PVA)/chitosan magnetic composite

Cobalt is one of the toxic radioactive elements and the removal of Co²⁺ from radioactive wastewater has received increasing attention in recent years. In this paper, polyvinyl alcohol (PVA)/chitosan magnetic composite was prepared and used for Co²⁺ removal. The effect of initial pH, contact time and initial Co²⁺ concentration on Co²⁺ adsorption was investigated. The kinetics, thermodynamic and isotherms of Co²⁺ sorption onto the composite were determined. The results showed that pseudo second-order equation could be used to describe the Co²⁺ removal process. The maximum sorption capacity was calculated to be 14.39 mg/g at pH 6.0 and 30 °C using the Langmuir model. The analysis of FTIR and SEM-EDAX were performed before and after Co²⁺ sorption onto the PVA/chitosan magnetic beads, revealing that the functional groups –NH₂ and –OH played main role in Co²⁺ sorption process. PVA/chitosan magnetic composite is promising adsorbent for removing Co²⁺ radioactive wastewater.     

Measurement and calculations of long-lived radionuclide activity forming in the fast neutron field in some ITER construction steels

Measurement and calculations of long-lived gamma-emitting radionuclide activity forming in the fission reactor fast neutron field were done, for some ITER construction steels. The activation was conducted in fast neutron irradiation channel of the MARIA research fission reactor (Poland). The dimensions of steel samples were 10 mm × 10 mm × 1 mm and mass was approximately 0.8 g. The neutron flux density was measured by means of activation foil method and unfolding technique; fraction of neutrons above 1 keV was 95%. The activation lasted 242 h and cooling took 100 days; the mean neutron flux density was 2.9E12 n/(cm² s) (neutrons above 500 keV are 53% of total) whereas total fluency 2.53E18 cm⁻². The activity measurements were done by means of gamma-ray spectrometry. Activity calculations were done by means of FISPACT-II code using the activation libraries EAF-2010 and TENDL-2011 and experimentally determined neutron flux. Measured activity of long-lived gamma emitting radionuclides was, in average, about 6.3 MBq/g 100 days after activation; the dominant radionuclides were ⁵⁸Co and ⁵⁴Mn (about 81% and 14% of total activity respectively). The C/E ratio differs for particular radionuclides and is in the range 0.86–0.92 for ⁵¹Cr, 0.93–1.21 for ⁵⁴Mn, 0.77–0.98 for ⁵⁷Co, 0.91–1.21 for ⁵⁸Co, 1.17–1.27 for ⁵⁹Fe, and 1.75–2.44 for ⁶⁰Co.     

Experimental investigation on cryogenic hydrogen adsorption of molecular sieves

Tritium extraction system (TES) is one of the most important components in the helium cooled solid breeder test blanket modules (TBMs) of ITER. TES will extract various isotopic species of hydrogen by the liquid nitrogen cooled molecular sieve adsorber beds (MSB). The cryogenic hydrogen adsorption properties of several kinds of molecular sieves have been investigated at the pressure of hydrogen of 100 Pa, 200 Pa, and 0.2 MPa in order to offer the suitable molecular sieve for the MSB in TES. The saturated hydrogen adsorption capacities of the MS5A-2 and MS13X-2 have been measured at 100 Pa hydrogen pressure. To demonstrate the hydrogen extraction from continuous He–H₂ purge gases, the MS5A-2 has been tested in circulating 99.79% He–0.21% H₂ mixture with a flow rate of 16.8 L/min. The results show that the globular MS5A-2 with a diameter of 3–5 mm can adsorb/desorb hydrogen quickly. The saturated hydrogen adsorption capacity of MS5A-2 is 7.55 ml g^?1 (NTP) and MS5A-2 could effectively extract trace hydrogen from mixture gases. As a result, this type of molecular sieve can be the candidate of the one in the MSB in ITER TBM.     

Design and commissioning of a TF coil power system using deep-cycle batteries for versatile experiment spherical torus (VEST)

A toroidal field (TF) coil power system has been designed and successfully commissioned to be suitable for the research objectives of VEST (Versatile Experiment Spherical Torus) which was recently constructed at Seoul National University. The TF coil power system for VEST is fabricated using a series–parallel connection of 200 deep-cycle batteries with 100 A h capacity so as to generate flat-top TF field of 0.12 T on magnetic axis for sufficiently long time up to hundreds of milliseconds. Ten battery modules are designed to operate independently through 10 magnetic contactor (MC) switches so as to produce toroidal magnetic field with various amplitudes and waveforms. During the initial start-up experiments of VEST, the modulation capability of toroidal magnetic field is successfully verified, showing possibility of its versatile utilization on various experimental topics in the future.     

三乙四胺改性壳聚糖磁性树脂对Th(Ⅳ)的吸附特性

先利用水相/有机相（W/O）反相乳液体系原位制备磁性壳聚糖树脂,再经三乙四胺接枝改性,制备氨基化磁性壳聚糖树脂（TETA-MCS）。TETA-MCS具有氨基含量高,易于磁分离的优点,可有效吸附Th(Ⅳ)。FTIR分析表明,TETA-MCS中的氨基、羟基可与Th(Ⅳ)形成O,N-Th(Ⅳ)络合物。吸附为自发吸热过程,吸附动力学符合准二级动力学模型。吸附等温线分别用Langmuir、Freundlich和Tempkin模型拟合,其中Langmuir模型拟合最好,25 ℃时Th(Ⅳ)最大吸附容量达133.3 mg/g。TETA-MCS利用0.2 mol/L HNO3-0.1 mol/L EDTA脱附再生,可重复使用多次。     

Damage recovery in ZnO by post-implantation annealing

ZnO bulk samples were implanted with 200 keV-Co ions at room temperature with two fluences, 1 × 10¹⁶ and 8 × 10¹⁶ cm^?2, and then annealed in air for 30 min at different temperatures up to 900 °C. After the implantation and each annealing step, the samples were analyzed by Rutherford backscattering spectrometry (RBS) in random and channeling directions to follow the evolution of the disorder profile. The RBS spectra reveal that disorder is created during implantation in proportion to the Co fluence. The thermal treatments induce a disorder recovery, which is however, not complete after annealing at 900 °C, where about 15% of the damage remains. To study the Co profile evolution during annealing, the samples were, in addition to RBS, characterized by secondary ion mass spectrometry (SIMS). The results show that Co diffusion starts at 800 °C, but also that a very different behavior is seen for Co concentrations below and above the solubility limit.     

Hydrogen-induced disproportionation characteristics of Zr(1 − x)Hf(x)Co(x = 0, 0.1, 0.2 and 0.3) alloys

Doping hafnium to partially substitute zirconium in ZrCo is a promising strategy to improve the ability to resist hydrogen-induced disproportionation. Herein, Zr(1 ? x)Hf(x)Co(x = 0,0.1,0.2, and 0.3) alloys were fabricated by arc melting and the effect of hafnium substitution ratio and temperature on their hydrogen-induced disproportionation was studied. Additionally, the disproportionated products were characterized by XRD, DSC and TDS. Results showed that disproportionation rate and the extent of disproportionation decreased with hafnium substitution ratio increasing from 0 to 30% and increased with temperature increasing from 400 °C to 550 °C. It was exciting that Zr0.7Hf0.3Co alloy had much better ability of anti-disproportionation than ZrCo in hydrogen pressure of about 200 kPa when temperature increasing from 400 °C to 550 °C, which was practical for tritium application.     

Effect of magnetic field on the growth of Be films prepared by thermal evaporation

Grain refinement of beryllium deposits is studied as a significant subject for beryllium capsule in the Inertial Confinement Fusion project. The Be films were prepared on the Si (1 0 0) substrates by thermal evaporation with and without a magnetic field, respectively. The two separate groups of prepared Be films were characterized. The results showed the grain diameter in the Be film transited from 300 nm to 18 nm and the surface roughness of the Be film decreased from 61 nm to 3 nm by application of the magnetic field during the deposition process of Be coating. However, the Be film grown with the magnetic field was easily oxidized in comparison with that grown without magnetic field due to the refined grains, and the oxidation was gradually decreased with the increase of etching depth in the Be film. The reason for grain refinement of Be film was also qualitatively described.     

Expanding argon plasma interacting with lithium surface

In this thesis, the interaction between Ar Plasma and lithium is studied by Langmuir probe and Spectrometer. We have studied the effects of the applied discharge current, the gas flow rate, the magnetic field on emission spectrum, electron temperature and electron density. The experimental results show that spectrum intensity, electron temperature and electron density all increase with the increasing discharge current, gas flow rate or magnetic field when the other experimental conditions were fixed, and it is also found that the intensity of Li-670.78 nm increases slowly at first and then increases rapidly, at last, it tends to be stable figure at the beginning of experiment. What is more, spectrum of lithium (670.78 nm) is also detected at the first diagnostic window (viewing window).     

Sorption studies of uranium and thorium on activated carbon prepared from olive stones: Kinetic and thermodynamic aspects

Activated carbon prepared by the chemical activation of olive stone was examined for the sorption of uranium and thorium from aqueous solutions. Precursor/activating agent (ZnCl₂) ratio (1:2) and 500 °C carbonization temperature were used for the preparation of the sorbent. The total sorption capacities were found to be 0.171 and 0.087 mmol g^?1 for uranium and thorium, respectively. The sorption of uranium and thorium was studied as a function of shaking time, pH, initial metal ion concentration, temperature and adsorbent concentration in a batch system. The sorption followed pseudo-second-order kinetics. ΔH° and ΔS° values for thorium and uranium sorption were calculated from the slope and intercept of plots of ln K_d versus 1/T. The positive values of ΔH° indicate the endothermic nature of the process for both metals and decrease in the value of ΔG° with rise in temperature show that the sorption is more favorable at high temperature.     

Oxidation of Zircaloy-4 by oxygen and the production of water

The interaction of isotopic oxygen (¹⁸O₂) with Zircaloy-4 (Zry-4) at 150 and 300 K has been studied using Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD) methods. AES reveals the oxidation of the Zry-4 surface, reflected in shifts of the Zr(MNV) and Zr(MNN) features by about 5.5 and 3.0 eV, respectively, for both adsorption temperatures. The O(KLL)/Zr(MNN) Auger peak-to-peak height ratios as a function of exposure show the same trends at both temperatures. Following ¹⁸O₂ adsorption at 150 or 300 K, TPD experiments show hydrogen desorption near 400 K that is attributed to the presence of a surface-stabilized form of hydrogen. Additionally, water (H₂¹⁸O and H₂¹⁶O) desorption below 200 K and above 700 K is observed after 150 K oxygen adsorption. However, after oxygen adsorption at 300 K the only significant desorption features are from isotopic water (H₂¹⁸O). These findings indicate that mass transport involving the near-surface region contributes to the observed desorption, and that this behavior is dependent on the original adsorption temperature. Charging experiments using D₂ prior to and after ¹⁸O₂ adsorption were also performed and support our conclusions about the role of surface–subsurface mass transport in this system.     

Potential application of a nanocomposite:HCNFe@polymer for effective removal of Cs (I) from nuclear waste

This study highlights new opportunities for the preparation of Cobalt Hexacyanoferrate(CoHCNF)@poly aniline nanocomposite as an adsorbent to efficiently remove Cs (I) ions from water. A chemical co-precipitation method was utilized to prepare CoHCNFe@poly aniline nanocomposite nanostructure. The TEM and SEM images of the product showed that it consists of semi-spherical particles with sizes ranging from 50 to 500 nm. Experimental parameters affecting Cs (I) sorption such as pH, adsorbent dosage, contact time, initial concentration of metal ion and temperature were studied. The maximum adsorption capacity (q) for cesium ions obtained from the Langmuir model at room temperature and 60 °C were 92.12 and 181.81 mg g⁻¹ respectively. It is clear that this adsorbent has effective removal properties for adsorption of Cs(I) from radioactive waste compared with other adsorbents.The kinetic data were analyzed by the pseudo-first-order and the pseudo-second-order kinetic models; consequently, the pseudo-second-order model was the best to describe the adsorption of Cs (I) ions. The equilibrium data were fitted to the three isotherm models: Freundlich, Langmuir and Dubinin–Radushkevich (D–R), and as a result the Langmuir model produced the best fit for the experimental data. Thermodynamic parameters showed that the adsorption of Cs (I) ions onto the nanocomposite was endothermic and spontaneous. The mechanism of Cs (I) ions sorption was discussed.     

Characterization of plasma jet ejected from a parallel-plate rail gun for simulating edge localized mode

A small plasma gun with parallel-plate configuration is fabricated to generate a bunch of plasma which is similar to ELM (edge localized mode) plasma, by taking advantages of its simplicity and cost-effectiveness. Prior to explore how to control the ELM-like plasma so as to relieve heat load on the divertor target, characteristics of a plasma jet ejected from the plasma gun are investigated using a quadruple Langmuir probe which is appropriate for measuring rapidly varying plasma parameters such as electron density, temperature, and ion velocity at the same time. The plasma density and ion velocity measured at 112 mm away from the exit are 3 × 10¹⁹ m^?3 and 11 km/s, respectively, which seem to be suitable for investigating next step research on the control of ELM-like plasma using various methods such as electromagnetic waves and high-voltage pulses. Also, the quadruple Langmuir probe is proven to be adequate for use in such experiments.     

三聚磷酸钠交联壳聚糖/纳米Fe~0复合膜对U(Ⅵ)的吸附特性

制备了三聚磷酸钠交联壳聚糖/纳米Fe~0(CS-Fe)复合膜,并将其用于吸附U(Ⅵ),考察了pH值对CS-Fe复合膜吸附U(Ⅵ)的影响,以及吸附动力学和吸附等温线。结果表明,吸附等温线符合双位点Langmuir模型,以CS-Fe复合膜的磷酸基团为主要吸附位,纳米Fe~0为次要吸附位。吸附动力学符合准二级模型,表明化学吸附是控速步骤。CS-Fe复合膜对U(Ⅵ)的饱和吸附容量(208.8mg/g)远高于壳聚糖膜对U(Ⅵ)的饱和吸附容量(131.6mg/g),这是由于壳聚糖促进了纳米Fe~0的分散以及纳米Fe~0还原U(Ⅵ)的共同作用。     

Study and optimization of boronization in Alcator C-Mod using the Surface Science Station (S3)

A Surface Science Station (S³) on the Alcator C-Mod tokamak is used to study and optimize the location and rate of boron film deposition in situ during electron cyclotron (EC) discharge plasmas using 2.45 GHz radio-frequency (RF) heating and a mixture of helium and diborane (B₂D₆) gasses. The radial profile of boron deposition is measured with a pair of quartz microbalances (QMB) on S³, the faces of which can be rotated 360° including orientations parallel and perpendicular to the toroidal magnetic field B_T ～0.1 T. The plasma electron density is measured with a Langmuir probe, also on S³ in the vicinity of the QMBs, and typical values are ～1 × 10¹⁶ m^?3. A maximum boron deposition rate of 0.82 μg/cm²/min is obtained, which corresponds to 3.5 nm/min if the film density is that of solid boron. These deposition rates are sufficient for boron film applications between tokamak discharges. However the deposition does not peak at the EC resonance as previously assumed. Rather, deposition peaks near the upper hybrid (UH) resonance, ～5 cm outboard of the EC resonance. This has implications for RF absorption, with the RF waves being no longer damped on the electrons at the EC resonance. The previously inferred radial locations of critical erosion zones in Alcator C-Mod also need to be re-evaluated. The boron deposition profile versus major radius follows the ion flux/density profile, implying that the boron deposition is primarily ionic. The application of a vertical magnetic field (B_V ～0.01 T) was found to narrow the plasma density and boron deposition profiles near the UH resonance, thus better localizing the deposition. A Monte Carlo simulation is developed to model the boron deposition on the different QMB/tokamak surfaces. The model requires a relatively high boron ion gyroradius of ～5 mm, indicating a B⁺¹ ion temperature of ～2 eV, to match the deposition on QMB surfaces with different orientation to B_T. Additionally, the boron ion trajectories become de-magnetized at high neutral gas throughput (～0.5 Pa m³ s^?1) and pressure (～2 Pa) when the largest absolute deposition rates are measured, resulting in deposition patterns, which are independent of surface orientation to B_T in optimized conditions.     

Concept design on RH maintenance of CFETR Tokamak reactor

CFETR which stands for Chinese Fusion Engineering Testing Reactor is a superconducting Tokamak device. The concept design on RH maintenance of CFETR has been done in the past year. It is known that, the RH maintenance is one of the most important parts for Tokamak reactor. The fusion power was designed as 50–200 MW and its duty cycle time (or burning time) was estimated as 30–50%. The center magnetic field strength on the TF magnet is 5.0 T, the maximum capacity of the volt seconds provided by center solenoid winding will be about 160 VS. The plasma current will be 10 MA and its major radius and minor radius is 5.7 m and 1.6 m respectively. All the components of CFETR which provide their basic functions must be maintained and inspected during the reactor lifetime. Thus, the remote handling (RH) maintenance system should be a key component, which must be detailedly designed during the concept design processing of CFETR, for the operation of reactor. The main design work for RH maintenance in this paper was carried out including the divertor RH system, the blanket RH system and the transfer cask system. What is more, the technical problems encountered in the design process will also be discussed.     

10 years of engineering and physics achievements by the Large Helical Device project

This article reviews 10 years of engineering and physics achievements by the Large Helical Device (LHD) project with emphasis on the latest results. The LHD is the largest magnetic confinement device among diversified helical systems and employs the world's largest superconducting coils. The cryogenic system has been operated for 50,000 h in total without any serious trouble and routinely provides a confining magnetic field up to 2.96 T in steady state. The heating capability to date is 23 MW of NBI, 2.9 MW of ICRF and 2.1 MW of ECH. Negative-ion-based ion sources with the accelerating voltage of 180 keV are used for a tangential NBI with the power of 16 MW. The ICRF system has full steady-state operational capability with 1.6 MW. In these 10 years, operational experience as well as a physics database have been accumulated and the advantages of stable and steady-state features have been demonstrated by the combination of advanced engineering and the intrinsic physical advantage of helical systems in LHD. Highlighted physical achievements are high beta (5% at the magnetic field of 0.425 T), high density (1.1 × 10²¹ m^?3 at the central temperature of 0.4 keV), high ion temperature (T_i of 5.2 keV at 1.5 × 10¹⁹ m^?3), and steady-state operation (3200 s with 490 kW). These physical parameters have elucidated the potential of net-current free helical plasmas for an attractive fusion reactor. It also should be pointed out that a major part of these engineering and physics achievements is complementary to the tokamak approach and even contributes directly to ITER.     

Development of a high energy pulsed plasma simulator for the study of liquid lithium trenches

To simulate detrimental events in a tokamak and provide a test-stand for a liquid-lithium infused trench (LiMIT) device [1], a pulsed plasma source utilizing a theta pinch in conjunction with a coaxial plasma accelerator has been developed. The plasma is characterized using a triple Langmuir probe, optical methods, and a calorimeter. Clear advantages have been observed with the application of a coaxial plasma accelerator as a pre-ionization source. The experimental results of the plasma gun in conjunction with the existing theta pinch show a significant improvement from the previous energy deposition by a factor of 14 or higher, resulting in a maximum energy and heat flux of 0.065 ± 0.002 MJ/m² and 0.43 ± 0.01 GW/m². A few ways to further increase the plasma heat flux for LiMIT experiments are discussed.