Hasil untuk "Nuclear engineering. Atomic power"

C. Kawan, S. Brezinsek, E. Wüst et al.

Tungsten (W) is the most promising plasma-facing material candidate for future deuterium–tritium (D–T) fusion reactors due to its favorable properties, such as low sputtering yield, low chemical reactivity, high melting point, and low intrinsic fuel retention. However, highly energetic neutrons from DT fusion reactions can cause displacement damage in the W lattice and enhance fuel retention. This affects the tritium cycle requirements and nuclear safety, as a tritium inventory builds up in the vessel. Therefore, diagnostics are required to quantify the D and T content in-situ in the plasma-facing and structural materials. Laser-induced Ablation Quadrupole Mass Spectrometry (LIA-QMS) is a promising method for quantifying fuel content with good spatial and depth resolution. LIA-QMS can be simultaneously applied with Laser-induced Breakdown Spectroscopy (LIBS). Combining both techniques provides the high depth resolution of LIBS with the quantification capabilities of LIA-QMS. This study compares D depth profiles recorded with pico-second LIA-QMS with Nuclear Reaction Analysis (NRA) with 3He beam on a displacement-damaged W sample. The comparison reveals the depth profiling capabilities, strengths, and weaknesses of LIA-QMS using picosecond lasers. A set of similarly self-damaged (10.8 MeV W3+ irradiated) ITER-grade W samples from PLANSEE was gently loaded with D in a low-temperature plasma at 370 K. The D concentration was varied by subsequent annealing of the samples at different temperatures in a vacuum after the D decoration. The ratio between D2 and HD, both contributing to the total D content, increases from 1:1 to 1:5, starting at the surface and extending to 4μm, with increasing depth. LIA-QMS shows a similarly high sensitivity (<0.05 at% D at a 15 nm average ablation rate (AAR)) as NRA (around 150-400 nm resolution). ps-LIA-QMS can be calibrated via a known amount of reference gas injections and deviates from the NRA results by a factor of 1.7 across all samples, which also includes non-volatile species. The laser-induced crater surface stays relatively flat for up to 4μm until surface structures start dominating the crater’s surface under the given laser parameters. μ-NRA in and around the craters shows complete removal of D inside the laser crater. Thermal effects due to the ps-pulses within the crater floor are indicated, but could not be quantified yet. In conclusion, this study shows a good agreement between ps-LIA-QMS, a potential in-situ method, and the reference ex-situ method NRA for D quantification. This paves the way for studies to investigate open questions about particle–wall interactions during the ablation process.

Chukwudi Azih

John Cui, Luke Lebel, Andrew Morreale et al.

Si Young Kim, Jung Han Kim

Seismic correlation can affect seismic probabilistic risk assessment results when components within the system have similar dynamic characteristics. While the fragility assessment methodology is well established, researches to evaluate and apply seismic correlation in fragility are still in progress. In this study, the seismic correlation coefficient (SCC) was quantitatively analyzed based on fragility assessment methods. In order to evaluate the SCC of several random variables associated with structure response in fragility assessment, a numerical analysis model of the structure was constructed and statistical analysis of the numerical results was performed. The SCC of the floor responses of the structural model considering random variables was evaluated from two perspectives. The first perspective involved applying variables individually or simultaneously when performing probabilistic structural analysis. The second perspective aimed to assess whether simplification of the structural analysis model affects the SCC. For this purpose, SCCs were calculated for each method and applied to a simplified failure sequence model to compare the combined fragility curves. The results of this study demonstrate the applicability of separation of variables method to the evaluation and generalization of the SCC for random variables of the fragility curve.

Shalu Atri, Kapil Verma, Bhawana Joshi et al.

Latent fingerprint development techniques have been evolved with the use of methods like powder dusting, cyanoacrylate fuming, chemical methods, and application of small particle reagents. These all have been gradually compromised due to their growing drawbacks in terms of their stability, specificity and even toxicity. Nano materials have great potential in identification of latent fingerprints due to their unique optical, magnetic, electric, and other properties. Oxides, silicates and composite materials of Nano-dimensions have significant role in different areas of Forensic science. Fluorescent nanomaterial has drawn a lot of attention because of its superior optical and chemical properties. The present review has focused on exploring the magnetic, luminescent and magnetic-luminescent properties of different nanomaterials in the detection of latent finger prints. Various factors like impact of synthetic methodology, morphology and structural parameter of the nano materials on finger print visualization have also been discussed.

Xin Wang, Ze Xu, Yulan Liu et al.

The elastoplastic mechanical behavior of Zircaloy-4 (Zr-4) cladding, coated with chromium (Cr) or FeCrAl on its surface, is explored under the coupled effects of multi-field coupling. Utilizing the Finite Element Software ABAQUS, simulations are conducted to calculate the evolution of stress and strain over two complete fuel cycles. Comparisons are drawn between the coated and uncoated Zircaloy-4 cladding materials. The results indicate that the application of surface coatings significantly mitigates stress levels in the cladding during the first fuel cycle. During the second fuel cycle, all three types of cladding exhibit relatively minor plastic strain, which is attributed to the unloading and reloading process between cycles. Notably, the plastic zone propagates from the interior to the exterior of the cladding. When compared to traditional Zircaloy-4 cladding, the coated cladding exhibits improved elastoplastic mechanical behavior. The operational mechanism of the coating for different stresses in cylindrical coordinates and its response to unloading and reloading cycles are also investigated. Specifically, the coated claddings exhibit an evident delay in reaching full plasticity compared to uncoated claddings. Furthermore, FeCrAl coating material initially shows good performance, and it needs to be verified in more aspects in the future. Results and Conclusions in this paper can provide reference and guidance for future experiments.

J. Dobaczewski, B. C. Backes, R. P. de Groote et al.

Electromagnetic interactions serve as essential probes for studying and testing our understanding of the atomic nucleus, as they reveal emergent properties across the nuclear chart. We analyse their corresponding observables, which relate to charge and current distributions in nuclei expressed through their multipole components. We focus on theoretical results obtained within nuclear density functional theory (DFT) to derive self-consistent, symmetry-restored nuclear wave functions along with their spectroscopic multipole moments. We demonstrate how these compare with experimental data. We also discuss potential improvements in the formulation of magnetic dipole operators by including two-body meson-exchange contributions. Discussions of exotic symmetry-breaking moments emphasise their importance for understanding fine details of fundamental nuclear interactions. Detailed derivations are provided in the accompanying Supplemental Material.

Giuliano Giacalone, Jiangyong Jia, Vittorio Somà et al.

High-energy collisions involving the $A=96$ isobars $^{96}$Zr and $^{96}$Ru have been performed in 2018 at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) as a means to search for the chiral magnetic effect in QCD. This would manifest itself as specific deviations from unity in the ratio of observables taken between $^{96}$Zr+$^{96}$Zr and $^{96}$Ru+$^{96}$Ru collisions. Measurements of such ratios (released at the end of 2021) indeed reveal deviations from unity, but these are primarily caused by the two collided isobars having different radial profiles and intrinsic deformations. To make progress in understanding RHIC data, nuclear physicists across the energy spectrum gathered in Heidelberg in 2022 as part of an EMMI Rapid Reaction Task Force (RRTF) to address the following question. Does the combined effort of low-energy nuclear structure physics and high-energy heavy-ion physics enable us to understand the observations made in isobar collisions at RHIC?

Jonathan Engel

This paper reviews the calculation of nuclear Schiff moments, which one must know in order to interpret experiments that search for time-reversal-violating electric dipole moments in certain atoms and molecules. After briefly reviewing the connection between dipole moments and CP violation in and beyond the Standard Model of particle physics, Schiff's theorem, which concerns the screening of nuclear electric dipole moments by electrons, Schiff moments, and experiments to measure dipole moments in atoms and molecules, the paper examines attempts to compute Schiff moments in nuclei such as $^{199}$Hg and octupole-deformed isotopes such as $^{225}$Ra, which are particularly useful in experiments. It then turns to ab initio nuclear-structure theory, describing ways in which both the In-Medium Similarity Renormalization Group and coupled-cluster theory can be used to compute important Schiff moments more accurately than the less controlled methods that have been applied so far.

Hyung Gon Jin, Suk-Kwon Kim, Sungbo Moon et al.

The blanket system is a crucial element in nuclear fusion power generation, tasked with tritium production and the efficient dissipation of the high thermal flux from the tokamak. Korea is in the process of developing the Helium Cooled Ceramic Reflector (HCCR) blanket, which stands as the forefront design among the nation's blanket systems. This paper presents accident analysis results of LOOP (Loss Of Offsite Power) accident for the HCCR blanket. Loss of power accident is one of the postulated events in the nuclear fusion system. This event may be caused by common failure of the external electrical grids or electrical faults in the site. The objective of this safety analysis is to assess the impact of the activation of an additional power supply within 90 seconds after an accident on the system temperature, and to evaluate the heat load that can be removed by the stagnated coolant in the CCWS (Component Cooling Water System) connected to the heat exchanger of the blanket system.

Jiulin Wu, Shuaibin Liu, Tao Hu et al.

The importance of determining the radon exhalation rate from water surface is emphasized by the increased use of radon and its daughter products as tracers in large-scale circulation studies of the atmosphere. There were many methods to measure radon exhalation from water surface. With the development of radon exhalation rate measurement methods and instruments on the surface of the soil, the rock and building materials, so the radon exhalation rate from water surface can be more accurately measured by applying these improved methods and instruments. In this paper, a cuboid accumulation chamber surrounded by foam boards and a RAD7 were used to measure the radon exhalation rate on the water surface at three different positions by Yixin lake. Each measurement was performed 2 h. The radon exhalation rate from the water surface was about 6 × 10−3 Bq m−2s−1. The thoron exhalation rate from the water surface also can be estimated, it is about 0.16 Bq m−2s−1. These results hint that the radon transmission from the lake bottom soil to water and then into the atmosphere.

WANG Guolian, LIU Xiaojing, HE Hui

BackgroundOscillatory conditions significantly affect the thermal-hydraulic characteristics of floating reactors, leading to changes in the growth of chalk river unidentified deposit (CRUD).PurposeThis study aims to investigates CRUD growth on fuel rod bundles under oscillatory conditions.MethodsFirstly, based on the data exchange method, the one-dimensional system program RELAP5 and the CFD (Computational Fluid Dynamics) program ANSYS Fluent were coupled to simulate the primary loop, and mathematical models of coolant flow and corrosion product deposition growth under oscillatory conditions were added to the simulation. Then, CRUD growth calculations and coolant flow mathematical models under oscillatory conditions were embedded into the multiscale simulation. Finally, the influences of oscillatory conditions on flow characteristics in rod bundle channels, fuel rod wall temperature, and CRUD growth were analyzed.ResultsThe simulation outcomes reveal that oscillation induces periodic variations in both the coolant flow rate and outer wall temperature of the rods. At lower axial heights, CRUD grows thicker on the rods near the peripheral wall. At higher axial heights, the CRUD distribution pattern tends to be consistent across all rods. The CRUD thickness distribution in the circumferential direction of the fuel rods tends to form an elliptical pattern in polar coordinates.ConclusionsFluctuations in flow rate and temperature can enhance erosion in the tangential direction of oscillation, diminish the deposition process, and result in varied CRUD distribution patterns at distinct positions.

DONG Tao;LIU Ximing;XING Guilai;WANG Zhentao;HUANG Yibin;LIU Jinhui;WU Zhifang

In large object radiation imaging system, the interaction between medium and high energy (MeV) X/γ-ray and matter is dominated by Compton scattering, which produces a large number of the scattered particles. And the influence of the scattered particles on the radiographic images has always been a tough problem that plagues the developers. And the rear collimator is commonly used to reduce the influence of the scattered particles and improve the quality of the radiographic images. At present, the relevant research mainly analyzes the distribution of the scattered particles in the detector array, but there is a lack of research on the distribution of the scattered particles on the surface of the inspected object. Based on the Monte-Carlo simulation model of the 60Co large object radiation imaging system, a common medium-density substance (iron plate) was selected as the inspected object, and the number distribution and energy distribution of the scattered particles were analyzed in detail when γ-ray penetrates iron plates from different positions and with different thicknesses. Also, the diffusion effect of the scattered particles and the shielding effect of the rear collimator on the scattered particles were analyzed. There are some results drawn in this paper. In the horizontal direction, the diffusion effect of the scattered particles caused by multiple Compton scattering is limited, and most of the scattered particles come from the area covered by the initial γ-ray beam on the object. About 90% of the scattered particles have a horizontal distribution range of 40-70 mm on the surface of the object, which will limit the shielding effect of the rear collimator. When the distance S between the iron plate (with the thickness of 100 mm) and the detector array is reduced to the limit of 500 mm for safe driving, there is approximately 39.74% of the scattered particles shielded by the rear collimator (Fe) with the collimation ratio of 20∶1 and the best thickness of 5 mm, while the ideal rear collimator absorbing all incident particles can shield about 63.21% of the scattered particles. When the distance S increases to 1 750 mm or more, the scattering effect of the rear collimator will be severe and cause an increase in the number of the scattered particles instead of performing its function of shielding the scattered particles, and a wider rear collimator may cause more serious scattering interference. Therefore, in the large object radiation imaging system, the scattering effect of the rear collimator cannot be ignored, and its shielding effect on the scattered particles is also limited.

D.E. Cherepanov, L.N. Vyacheslavov, V.A. Popov et al.

New generations of fusion devices need alternative plasma-facing materials. The currently approved material composition for the first wall and divertor of the ITER tokamak has a number of disadvantages: insufficient resistance to thermal shock, sputtering of microparticles into plasma and high atomic number Z of the armor material. A promising but largely untested idea is the proposal to use high-temperature ceramics as armor materials for the most heat-loaded plasma-facing components of new-generation fusion devices. Among the advantages of ceramics are the low Z and high enough resistance to intense heating. More research is needed that would help to understand how the material withstands high heat fluxes during transient plasma events. This work is devoted to the description of an experimental method that makes it possible to estimate the critical temperature at which the damage of ceramics begins as a result of a thermal shock of submillisecond duration. As a demonstration of the efficiency of the method, the critical temperature for hot pressed B4C under thermal shock was determined: its value was about 1200–1400 K.

W. Zholobenko, J. Pfennig, A. Stegmeir et al.

The understanding and the predictive capability for turbulence in the plasma edge and scrape-off layer (SOL) are crucial for the development of magnetic confinement fusion reactors. To this end, we characterise turbulent transport across the edge and SOL of the diverted ASDEX Upgrade tokamak in attached L-mode conditions by means of validated, global simulations. The collisionality is controlled by the divertor neutrals density, as their ionisation increases the plasma density and decreases the temperature. The radial E×B particle and heat transport, quantified by effective diffusivities, rises strongly with collisionality. The modest increase in fluctuation amplitudes is not a sufficient explanation. The reason is shown to be the destabilisation of resistive drift-ballooning modes, resulting in larger phase shifts between the pressure and electrostatic potential. The transport varies both radially and poloidally. Due to its ballooning nature, radial transport is close to zero on the inboard mid-plane. On the outboard mid-plane, significant transport is driven in the SOL by large filaments (blobs) with amplitudes of up to 250% of the mean, propagating ballistically from the separatrix to the wall. This non-local transport leads to large radial variations of diffusivities, as they do not necessarily correlate with the local gradient. Ion temperature fluctuations in the plasma edge are shown to be involved in blob seeding at the separatrix, and are the largest in the SOL. Radial diffusivities peak at the top and bottom of the device, since gradients are flatter there due to the flux expansion while the cross-field flow is sustained by streamers—a feature which should be considered in mean-field transport modelling. The increase of SOL E×B transport with collisionality is likely fostered by the simultaneously decreasing radial electric field, resulting from a flattened electron temperature profile. Large amplitude blobs are a hazard for plasma facing components of fusion reactors, but they could be restrained by control of SOL collisionality.

ZHAO Ri;LIU Na

In view of the limitations of existing gamma spectrum analysis methods on nuclides identification and activity evaluation, a special deep learning model was proposed which consists of 51 layers and more than 107 parameters. Based on multitude residual convolutional modules, this model can extract characteristics of whole gamma spectrum hierarchically and comprehensively and keep its numerical stability at the same time. The output of this model was also specially designed so that it can predict the energy and quantity of the gamma rays emitted by nuclides directly, no longer rely on the preset nuclide library. After model construction, the testing experiment was carried out. A NaI-type Whole-Body-Counter was chosen to measure the gamma spectrum of human body. The corresponding digital model was constructed and lots of simulated spectra were generated by Monte Carlo simulation method. For training, the data set was acquired by setting the energy and quantity of gamma ray source particles randomly in each spectrum, and for testing, 9 radionuclides were selected to determine the source particle setting during testing data set simulation. When testing, besides the constructed deep learning model, three existing methods were also tested for comparison. Results show, deep learning model performs best with 93.3% nuclide identification rate and 8.6% average activity predicting error, while traditional peak-analysis method identifies the least nuclides (62.3% identification rate), and gives most inaccurate activity values (28.3% average error), and spectrum-reconstruction method and shallow ANN model also show their limitation when analysis is carried out, with 78.2%, 81.3% identification rate and 18.7%, 14.8% average activity error respectively. In real measurement experiment, a human physical phantom containing 134Cs, 137Cs, 57Co, and 60Co was measured for 10 times, and results of the four involved methods were compared. Result indicates that deep learning model identifies 6 gamma rays contained in the spectrum correctly and predicts the activities of four nuclides with less than 10% error. In contrast, peak-analysis method incorrectly treats the scattering structure in the low energy spectrum region as a gamma ray related peak, and the activity evaluation errors of the three compared methods were all relatively high. The reasons of the performance difference among the involved methods were further discussed. The peak-analysis method utilizes only the peak region characteristic in the spectrum ignoring the rest part, so the weak and overlapped peaks are easy to be missed and false peak structures can also be identified incorrectly. Meanwhile, its activity assessing process involves continuum subtraction and net counts fitting procedures, which could introduce high uncertainty. Spectrum-reconstruction method though reconstructs the nuclide emitting spectrum based on whole measured spectrum, and it cannot ensure its accuracy due to the numerical difficulty of the inverse-solving problem. Shallow ANN model, when applied to nuclides identification among limited nuclide categories, shows good results in previous research. However, it’s unable to retain the performance when predicting more complex information in this paper, because of its very limited ability on characterizing and learning. The results of testing based on simulated as well as measured spectrum confirm the accuracy and reliability of the deep learning model for gamma spectrum analysis. Based on enhanced characteristic extracting ability and highly numerical stability, the proposed method is possible to be implemented in various radiation detecting applications in future.

G. V. Kulakov, A. Vatulin, S. A. Ershov et al.

G. Bochek, А.A. Kapliy, S. Kiprich et al.

The use of detection modules based on a silicon planar uncooled detector and a scintillator in combination with readout electronics makes it possible to create detection complexes for spectrometric detection of X-ray and gamma radiation in various fields of research, including nuclear physics, nuclear power engineering, high-energy physics, medicine, etc. The results of a study of detection complexes with silicon detectors with an active area of 22 and 55 mm and cesium iodide scintillators doped with thallium in the energy range from 50 keV to 0.662 MeV are presented.

ZHU Xin;WANG Zhiming;LUO Changkai;NI Lei;ZHONG Chunlai;FAN Tieshuan

A key question about the fission process of a heavy nucleus is to probe the nuclear potential energy landscape and its evolution from the single groundstate compound nucleus over the top of the fission barrier and further to the scission point, finally terminating in the formation of fission fragments. In this work, a macromicroscopic model was established to calculate the fission properties for uranium elements. The total potential energy as a function of deformation parameters was divided into a smoothly varying macroscopic part and a microscopic part representing quantum effect correction. The nuclear shape was described by the SwiateckiNix threequadraticsurface (3QS) parametrization, which could accurately represent the nuclear shape evolution all the way from the ground state to the scission configuration. The macroscopic part of the nuclear potential energy was calculated by the LSD (LublinStrasbourg drop) model. In the microscopic part, the foldedYukawa potential was used as the independent particle potential, whereas the shell correction method of Strutinsky and the smooth BCS pairing model were used to calculate the deformation energy of the compound nucleus. For the 234U compound nucleus, a potential energy surface (PES) with 5 906 250 lattice points was calculated and analyzed in a fivedimensional deformation space given by the 3QS parametrization. The watershed algorithm was used to search the fission paths on the fivedimensional PES for 234U. For different nuclear shapes, there are two well separated fission paths, asymmetric and symmetric, which share the same inner barrier and deviate at the point of second minimum, and finally end at two different points of the PES. During reaching scission points, the asymmetric fission pass will cross a new barrier with lower height than the outer barrier, but the height of the new barrier needs to be crossed is higher than the outer barrier for the symmetric fission path. The heights of fission potential barrier and the nuclear shapes at special positions, such as the saddle point and the scission point, were given for 234U. The comparison of our results, the inner barrier height and outer barrier height, with available experimental data and other’s theoretical results confirms the reliability of our calculations. The calculated results of this work, especially the outer barrier in the large deformation area, are in good agreement with the experimental data of RIPL library and Moller’s calculation, which means that the 3QS parametrization might be closer to the real nuclear shape than the generalized Lawrence shape description specially in the large deformation region.

Haiyan Peng, Fu Jin, Chao Li et al.

Purpose: To build an image-scanning protocol of Catalyst HD and to investigate the impacts of different colors on gains (Ga), integral times (Ti), and setups using this system. Methods: Thirty-eight cards with different skin tones were studied, and the color difference ΔE was calculated based on a reference color in the RGB (R: red, G: green, B: blue) space. Correlations were investigated among ΔE, Ga, and Ti. After routine setup verification, the card position changed from −5 mm to 5 mm with a step size of 2 mm, and they were measured by Catalyst HD simultaneously. The position differences were calculated to evaluate setup errors. Results: As Ga changed from 100% to 1000%, the natural logarithmic function of Ti (lnTi) linearly decreased with a constant slope of −0.002. If the reference color had an RGB value of (200, 172, 153), lnTi increased linearly with slopes of 0.006 and 0.007 for the main and side cameras respectively, as ΔE increased. Moreover, there were significant positive correlations between measured positions and true values. The correlation coefficient rpos changed as a sigmoid function of ΔE. There was a ΔE threshold of 254.0 for color detection. The detection was different for different colors. Additionally, rpos depended on the RGB values, curvature, edge and area of a region-of-interest. Conclusions: There are close correlations among ΔE, Ga, and Ti, and ΔE has an impact on setup accuracy using Catalyst HD.