Nuclear Analysis最新文献

The concentration distribution in blend of polyethylene oxide (PEO)/polycaprolactone (PCL) and subsequent crystallization were investigated with differential scanning calorimetry, in-situ small angle X-ray scattering and wide angle X-ray scattering. By using PEOs with a molecular weight of 1 × 10⁶ g/mol (PEO1M) and 1 × 10⁵ g/mol (PEO100k), respectively, it is revealed that in initial blend the concentration of PEO1M in PEO-rich region is higher than that determined by miscibility. This non-equilibrium distribution induced by crystallization is maintained after melting, since slow relaxation of PEO1M hinders the redistribution process. Crystallization behavior of blend with 25 % of PEO1M at different melting temperatures was further investigated. The crystallinity shows no dependence on melting temperature, while the long period of PEO1M decreases continuously when melting temperature exceeds 140 °C. This decrease indicates more PCL chains diffuse into PEO-rich regions with increasing temperature and molten PCL chains reduce the entanglement number of PEO1M as solvent. Moreover, the periodicity of PEO1M lamellae becomes worse when crystallization proceeds faster, which is related to slower exclusion of PCL chains.

Although nuclear power plants produce about 20% of India's power, the risk posed by radioactive leakage is considerable. Radiation leakage detection devices must be installed in all nuclear power plants to ensure that avoidable catastrophes never occur again and that the loss of human life is prevented. A safe atmosphere for inhabitants and workers may be ensured by keeping a consistent radiation level in all applications that use radioactive material. Complementary Metal-Oxide Semiconductor technology, or CMOS, uses complementary and symmetrical MOSFETS for logic-based functions in various applications, such as analog circuits (CMOS sensors). The Internet of Things (IoT) extends the power of the Internet beyond computing devices to a multitude of other things, processes, and environments. The main objective of this paper is to find a better and more creative solution for radioactive leakage detection techniques over present-day techniques. In this paper, the Authors aim to integrate CMOS and IOT applications for radioactive leakage detection methods on an industrial level. Within this paper, we have given brief descriptions of CMOS and IoT with their types, functions, methodology, and applications. CMOS is considered to be the most sophisticated and precise technology that can be employed to measure radiation leaks of all types (alpha rays, beta rays, gamma rays, and neutrons). With the help of IOT, massive disasters can be averted using complex alert systems. A well-coordinated combination of the two technologies has the potential to vastly increase leak detection potential and consistency. The study's major goal is to develop new and improved technology for detecting released radiation in the industry in order to obtain real-time information about the material leaked, as well as the location of the leak and the quantity of leakage that occurred, in order to reduce the danger of a natural catastrophe.

The thermodynamic parameters of the complexes of Th with N-methylethylenediamine-N,Nʹ,Nʹ-triacetic acid (MEDTA; denoted as H₃L with three dissociable protons) were studied. Potentiometry and microcalorimetry were used to determine formation constants and enthalpies, respectively. Thermodynamic analysis revealed two successively formed complexes, namely, ThL⁺ and ThL₂²⁻ (L³⁻ denotes the totally deprotonated MEDTA). Results indicated that both complexation reactions were exothermic and driven by entropic force. The first stepwise reaction (Th⁴⁺ ​+ ​L³⁻ = ThL⁺) was mainly driven by entropy with minimal effect on enthalpy change. The second stepwise reaction (ThL⁺ ​+ ​L³⁻ = ThL₂²⁻) was more exothermic and showed less entropic change than the first stepwise reaction. The strong chelation of MEDTA would inhibit the hydrolysis of Th⁴⁺ and increase solubility.

In order to have a deep understanding of the tritium migration and release mechanisms in ceramic breeders, computer simulation of the tritium release behavior of Li₄SiO₄ ceramic breeder was performed by using an improved tritium release model. The influences of various factors, such as surface adsorbed water, water vapor in the purge gas, hydrogen in the purge gas, grain size and tritium production amount, on the tritium release process were systematically investigated. The simulation results have shown that: 1) The surface adsorbed water and water vapor in the purge gas can remarkably facilitate tritium release as tritiated water (HTO) in low temperature region (typically <450 °C); 2) Adding hydrogen to the purge gas is effective to promote tritium release as tritium gas (HT), but the effectiveness is sensitive to surface adsorbed water and water vapor in the purge gas; 3) Large grain size and tritium production amount can relatively weaken the effects of surface adsorbed water and water vapor in the purge gas. In general, the simulation results were consistent with the observations in tritium release experiments, which were helpful to further elucidate the complex behavior of tritium release from Li₄SiO₄.

Uranium oxides are tightly related to the whole nuclear fuel cycle in the nuclear industry. However, the understanding of the chemical states in mixed valence uranium oxides remains scattered and deserves more exploration. The current study aims to recognize the valences of uranium in U₃O₈ by a simple X-ray photoelectron spectroscopy (XPS) investigation. U₃O₈ mixed with TiO₂ was photocatalytically reduced under UV or X-ray irradiation, and the chemical states were in-situ determined by XPS. Under UV irradiation, the shoulder peaks at 380.9 eV (U 4f_7/2) and 392.7 eV (U 4f_5/2) gradually increased, and an enhancement in intensity was also observed at 399.6 eV, which is the characteristic of U(V) satellite. Therefore, it was proved that the shoulder peak originated from U(V), and U₃O₈ consists of U(V) and U(VI). Under the irradiation by X-ray, the main lines of U 4f shifted lower by ∼0.8 eV, and a new satellite at ∼397.6 eV appeared and grew with increasing irradiation time, proving the generation of U(IV). This in turn verified that the shoulder peaks in primary U₃O₈ should be U(V) rather than U(IV). Therefore, it was confirmed by the current study that there are two-U(V) and one-U(VI) in each U₃O₈ unit cell.

The neutron-induced cross sections are of great significance for the design of nuclear devices and advanced reactors for the nuclear energy production. At CSNS Back-n white neutron source, new measurements of the fission cross sections and total cross sections are performed with two sets of Day-one spectrometers based on the multi-cell fast fission ionization chamber (FIC). The neutron-induced ^236,238U fission cross sections relative to ²³⁵U from the fission threshold energy to 200 MeV were measured by using the TOF method and the Fast Ionization Chamber Spectrometer for Fission Cross Section Measurement (FIXM) in the single/double bunch mode of Back-n. The experimental uncertainties are analyzed in detail, and the results from the two modes are consistent. The measured ^236,238U/²³⁵U fission cross section ratios are compared with previous experiments and evaluations. The ^236,238U(n,f) cross sections are obtained based on the standard ²³⁵U fission cross section. The neutron total cross sections of carbon and aluminum in the energy region from 1 eV to 20 MeV have been measured by using the TOF method and transmission method based on the Neutron Total Cross Section Spectrometer (NTOX) in the double bunch mode. The total cross section results after unfolding are in good agreement with the previous measurements as well as the broadening of the ENDF/B-Ⅷ.0 evaluation with Gaussian function within the experimental uncertainty. The present results provide the experimental data for further measurements, relevant evaluations and the design of nuclear system.

With as goal of improving on traditional α-ZrP, four zirconium phosphonate materials were prepared as potential adsorbents for the removal of ⁹⁰Sr from nuclear wastewater. A typical sol–gel method was used, for phosphonates: hydroxy ethylidene diphosphonic acid (HEDP), amino tri-(methylenephosphonic acid) (ATMP), ethylene diamine tetra-(methylene phosphonic acid) (EDTMP), and diethylenetriamine penta-(methylenephosphonic acid) (DETPMP) to give ZrP-HEDP, ZrP-ATMP, ZrP-EDTMP and ZrP-DETPMP, respectively. These materials exhibit a similar crystalline phase to α-ZrP, but have a completely different morphology. After loading of these organophosphonate groups, the original sheet-morphology disappears, and the materials were consistent with smaller particles. However, the loading of organophosphonate groups expands the inter-layer distances. Remarkably, these materials have a stronger ability to remove Sr²⁺, with higher adsorption capacity than α-ZrP, especially ZrP-ATMP due to its wider layer distance. The maximum adsorption capacities for Sr²⁺ are 158 mg g⁻¹, 175 mg g⁻¹, 115 mg g⁻¹ and 76 mg g⁻¹for ZrP-HEDP, ZrP-ATMP, ZrP-EDTMP and ZrP-DETPMP, respectively, while that ofα-ZrP is 55 mg g⁻¹. The higher adsorption capacities of these zirconium phosphonate materials is attributed to their wider interlayer spacing, allowing more room for Sr²⁺ to move.

To study inverse effect of hydrogen isotopes in LaNi₅ for hydrogen isotope separation at ambient temperature, temperature dependence of hydrogen isotope effect in LaNi₅－H(D) system was investigated in the temperature range -70 °C to 3 °C. Isotherms of hydrogen isotopes were tested in an automated Sieverts apparatus with a thermostat, and pressure differences were studied between H₂ and D₂. Isotope exchange process was carried out and H₂－HD－D₂ equilibrium was judged by online chromatography, separation factors were calculated to investigate the thermodynamic isotope effect. In the H₂, D₂ isotherms, average time interval (0.5h) between each equilibrium point was relatively short due to high precision temperature control. From the plateau pressures at a constant hydrogen (or deuterium) concentration in LaNi₅ (2D or 2H atoms/mole of LaNi₅) the partial molar enthalpies, ⊿H, and entropies, ⊿S of formation were calculated. ⊿H and ⊿S kept good accordance with the values from references, which indicated good performance of the Sieverts apparatus. The isotope exchange equilibrium was reached within 1h. The results showed that ratio between H₂ pressure and D₂ pressure, r(H－D) = P(D₂)/P(H₂), dropped as temperature decreased and the inverse effect was found (r(H－D)<1.0) below -5 °C according to the absorption branch of isotherms, whereas the effect was estimated to appear below 60 °C from the desorption branch. The separation factor of the H₂－HD－D₂ mixture, decreased as temperature increased and the inverse effect happened below -20 °C. The inverse effect was affected by the isotherm hysteresis and HD existence.

Estimation of both the surface tritium and tritium in bulk in key materials of fusion reactors is of great importance for tritium safety and the management of tritium-contaminated material. For the further quantitative analysis of tritium in solids, the elaborate BIXS spectra were calculated based on Monte Carlo simulation. Four types of tritium depth profile were considered to evaluate the quantitative estimation method. It is found that the attenuation of X-rays in tungsten depends on both the energy of X-rays and the depth of X-rays. The evaluation of tritium amount in surface layer indicated that the intensity of Ar(Kα) peak could be used to evaluate the surface tritium within 400 nm from the surface in most cases and the deviations were less than 9% in the calculation. The intensity of both W(Lα) X-rays and the high energy X-rays can be employed to roughly estimate the total tritium amount. For linearly decreasing and exponentially decreasing distribution, the maximum calculation deviations were 24.9% and 28.8%, respectively. While for Gaussian distribution, the maximum deviations were 146% and 53%, respectively. And it can also be used for tritium estimation in other materials.

The motion of a single bubble in a 2-D vertical channel filled with stagnant or moving fluid is simulated for various sets of conditions using the computational fluid dynamics(CFD) method. The volume of fluid (VOF) model is applied to track the interface of the bubble. Corresponding results are compared with experimental and theoretical studies, and good agreement is achieved. Two-phase flows composed of various fluids are simulated to check the impact of physical properties on bubble dynamics, and buoyancy is found to have a key influence on the bubble rising behavior, including both the trajectory and the terminal rising velocity. The dimensionless number Bu is introduced to characterize this effect, and a larger Bu leads to a larger bubble rising velocity. Three other dimensionless numbers Eo, We, and Mo are introduced to study the bubble deformation which can be characterized by aspect ratio E, and an approximately linear relationship is found between E, Eo, and bubble size. Inertial force is proved to influence the bubble motion significantly in moving fluid, whose velocity dominates the bubble terminal speed. The simulation of motion for two bubbles is also performed and investigated detailedly.