Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-22
Abstract： Light Gradient Boosting Machine (LightGBM) and Random Forest (RF) algorithms were used to predict the apparent diffusion coefficient of Se(IV) in compacted bentonite. Seven instances of Se(IV) were measured using through-diffusion method. LightGBM (R2 = 0.98 and RMSE = 0.025) exhibited superior predictive accuracy with a training dataset consisting of 956 instances and eight input features from Japan Atomic Energy Agency (JAEA-DDB). Shapley Additive Explanation and Partial Dependence Plots analyses revealed valuable insights into the diffusion mechanism of adsorbed anion obtained by evaluating the relationships between the apparent diffusion coefficient and the dependency of each input feature.
Peer Review Status:
Awaiting Review
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-21
Abstract： The cooling storage ring (CSR) external-target experiment (CEE) is a spectrometer used in construction to study the properties of nuclear matter in high-baryon density regions at the Heavy-Ion Research Facility in Lanzhou (HIRFL). This study presents the design, simulation, manufacturing, and testing of a half-size prototype of a multi-wire drift chamber (MWDC) for the CEE. First, the performance of the MWDC connected to home-made electronics was simulated. The results demonstrated that an energy resolution of 18.5% for 5.9-keV X-rays and a position resolution of 194 um for protons can be achieved by the current design. Because the size of the largest MWDC reached 176 × 314 cm, a set of 98 × 98 cm prototypes was built using the new techniques. The positioning accuracy of the anode wires in this prototype exceeded 20 um. After optimization using commercially available electronic devices, the prototype achieved an energy resolution of 19.7% for a 55Fe X-ray source. The CEE-MWDC detector and electronics were simultaneously tested. An energy resolution of 22% was achieved for the 55Fe source; the track residuals were approximately 330 um for the cosmic rays. The results demonstrate that the current design and techniques meet the requirements of the CEE-MWDC array.
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-18
Abstract： [Background] Due to the independence of traditional neutron and density measurement instruments, in order to improve the safety and efficiency of geological information.[Purpose]Integrate the design of existing neutron and density instruments to merge the neutron density components And analyze in detail the gamma influencing factors in integrated design.[Methods] In order to investigate the influence of the distance between neutron and gamma sources on detector measurements, Monte Carlo simulation was used to analyze detector counts and energy spectra at different distances between neutron and gamma sources, and the results were validated under different rock and density conditions.[Results] Keeping the true instrument source distance, neutron source intensity and other parameters unchanged, the neutron radiation field has no significant impact on the density measurement results when the neutron and gamma sources are 410mm apart, and the absolute error of the inversion density is less than 0.015g/cm3. By changing the neutron source intensity to explore the impact of source intensity on integrated research, and simulating multiple neutron sources with different intensities, it can be found that as the neutron source intensity gradually increases, the optimal distance between the neutron source and gamma source gradually increases and presents a quadratic function relationship.[Conclusions] Based on such findings, the distance between the two sources can be flexibly determined based on the strength of the neutron source, enabling rapid performance evaluation of on-site instrument testing and providing theoretical guidance for integrated design.
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2024-05-16
Abstract： As a candidate material for fusion reactors, the main components of low activation ferrite steel (martensitic steel) are Fe and Cr. In actual working conditions, helium produced by fusion reactions will enter the material, causing microscopic defects and radiation damage, affecting the material's resistance to radiation (helium embrittlement phenomenon) and other physical properties. This article simulates the interface of Fe Cr alloy, the main material of the reactor, through first principles calculations. He atoms are doped at different substitution and interstitial sites, and the formation energy of each structure is calculated after optimizing its structure. The stability of He atoms at different positions on the Fe Cr interface is obtained. At the same time, by calculating the volume, it was found that He would cause significant lattice distortion at the Fe octahedral gap near the interface. Based on the analysis of electronic density of states, it is inferred that this is the result of the hybridization of He, Fe, and Cr atoms at specific positions, provide a theoretical basis for the next research on the microscopic defects and physical and chemical properties of nuclear grade stainless steel.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-15
Abstract： [Background]Active neutron interrogation (ANI) measurement systems can quantify the fissile mass of special nuclear materials (SNMs) using neutrons and are widely used in nuclear safeguard fields. However, the hydrogen-containing matrix in the waste drum reduces the signal of delayed neutrons and limits the fissile mass measurement precision of the ANI system. [Purpose]It is essential to ensure that the fissile mass evaluation of the SNM is independent of matrix material and to improve the assay performance of the ANI system in nuclear safeguard measurements. [Methods] Therefore, based on the flux monitor response, a new matrix correction method was developed on the basis of traditional correction methods in this work. [Results]It turned out that the effect of various hydrogen densities on the delayed neutron count rate differs. For U3O8 materials with different enrichment and distribution, matrix effect may result in an overestimation of up to ~7 times in the observed mass of 235U. For U3O8 materials with different 235U enrichments and distribution states, both the traditional correction method and the new correction method can effectively reduce the influence of the matrix material on the measurement of SNM mass. But compared with the traditional method, the new method can achieve better correction results. For the case where U3O8 material is located in the center of the matrix, the average relative deviation of 235U mass obtained by the new correction method is 13.6%, while for the case where U3O8 material homogeneous dispersed throughout the matrix, the average relative deviation of 235U mass obtained by the new correction method is 7.78%. [Conclusions]These results confirm the effective performance and practicality of the new correction method.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-12
Abstract： [Background]: The primary heat exchanger (PHX) used in the 10MWt Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory (ORNL), is a U-tube heat exchanger, where the shell side (hot side) contains the fuel salt from the primary loop, while the tube side (cold side) carries the coolant salt from the secondary loop. [Purpose]: This study aims to deepen the understanding and mastery of the operational characteristics of molten salt heat exchangers, and to accumulate experience in their design and operation within molten salt reactors. [Methods]: the MSRE-PHX is modeled based on the design parameters, theoretical calculations for shell and tube hear exchanger (Kern method and Bell-Delaware method), software simulation (HTRI Xchanger Suite) and computational fluid dynamics (CFD) simulation are performed, critical performance metrics, such as the heat transfer coefficient, the pressure drop, and the heat transfer power, are obtained and compared to the MSRE operation data. [Results]: The findings indicate that the discrepancies from theoretical calculations, HTRI software, and CFD simulations, are all within acceptable margins to the experimental data. Notably, the greatest variance was found with the Kern method, which showed a deviation in heat transfer quantity of about 15%, while the smallest discrepancy was observed in the overall heat transfer coefficient calculated using HTRI software, differing by merely 0.16% from the experimental data; [Conclusions]: All of the methods are suitable and applicable for designing and studying a molten salt shell and tube heat exchanger; moreover, the CFD simulation can provide fine localized details of the heat transfer and flow of the molten salt fluid. This offers substantial theoretical support and practical guidance for the future design and improvement of molten salt heat exchangers.
Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-05-12
Abstract： Background : Electron cyclotron resonance heating (ECRH) is an important heating and plasma current control method for the HL-3 tokamak. Microwave inject into plasma through the launcher, which is an important part of the ECRH system. Purpose : Design and test the ECRH launcher system of the HL-3 tokamak. Methods : Overall planning was carried out for the launcher system. Designed the transmission path and structure of the launcher. Simulated and calculated the effect of microwave injection. Tested the transmission angle and rotation speed of the launcher, and calibrated the rotation angle of the launcher. wz1 Results : The optical path design of the No. 2 upper launcher has been completed. The full range response time of the equatorial launcher is less than 90ms; The full range response time of the No. 1 upper launcher is less than 190ms. Conclusions : The optical path design of the No. 2 upper launcher meets the requirements. The control of the equatorial launcher and the No. 1 upper launcher is precise and fast, meeting the requirements for experimental use of the tokamak.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-12
Abstract： Accurate measurement of the control rod worth in physical tests is of great significance for the safe operation of the reactor. The research on the calculated method of multi-group space-time neutron kinetics based on hexagonal geometry was carried out, and the advanced dynamic rod worth measurement suitable for hexagonal geometry was studied. This method owns high accurate and fast, which has a wide range of applications. The results show that the deviation between the control rod worth measured by the method and the theoretical value is within 10%, which demonstrated that the calculation accuracy of this method is high. The results also show that the calculation time of the method is short, and the calculation efficiency is high.
Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-05-12
Abstract： Background The high voltage power supply is an important part of the neutral beam injection heating system, which determines the beam energy and the quality of the extraction beam current. With the gradual increase of voltage level, the PSM high voltage power supply cannot meet the experimental requirements. Purpose In order to realize the fast switching of injected power for neutral beam modulation, an inverter high voltage power supply based on super capacitor energy storage is proposed. Methods Super capacitor energy storage is adopted to reduce the required grid capacity and minimize the impact on the grid. The DC-DC resonant converter structure with soft-switching technology is used to improve the response speed of the power supply and reduce the switching loss of the switching devices. Design power module circuit topology, build system model and calculate relevant parameters based on power supply performance specifications. The charging circuit and main loop PSIM simulation model are established, and the power supply performance indexes are simulated and verified. Build the test prototype of inverter power supply module and complete the test of relevant performance indexes. Results and Conclusions After simulation and experimental verification, the power module is able to achieve a stable output of 1600V/50A, which meets the design requirements of 6MW/120kV.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-11
Abstract： The Dynamics beamline (D-Line), which combines synchrotron radiation infrared spectroscopy (SR-IR) and energy-dispersive X-ray absorption spectroscopy (ED-XAS), is the first beamline in the world to realize concurrent ED-XAS and SR-IR measurements at the same sample position on a millisecond time-resolved scale. This combined technique is effective for investigating rapid structural changes in atoms, electrons, and molecules in complicated disorder systems, such as those used in physics, chemistry, materials science, and extreme conditions. Moreover, ED-XAS and SR-IR can be used independently in the two branches of the D-Line. The ED-XAS branch is the first ED-XAS beamline in China, which uses a tapered undulator light source and can achieve approximately 2.5 × 1012 photons/s•300 eV BW@7.2 keV at the sample position. An exchangeable polychromator operating in the Bragg-reflection or Laue-transmission configuration is used in different energy ranges to satisfy the requirements for beam size and energy resolution. The focused beam size is approximately 3.5 μm (H) × 21.5 μm (V), and the X-ray energy range is 5–25 keV. Using one- and two-dimensional position-sensitive detectors with frame rates of up to 400 kHz enables time resolutions of tens of microseconds to be realized. Several distinctive techniques, such as the concurrent measurement of in-situ ED-XAS and infrared spectroscopy, time-resolved ED-XAS, high-pressure ED-XAS, XMCD, and pump–probe ED-XAS, can be applied to achieve different scientific goals.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-11
Abstract： Carbon-based nanomaterials have important research significance in various disciplines, such as composite materials, nanoelectronic devices, biosensors, biological imaging, and drug delivery. Recently, the human and ecological risks associated with carbon-based nanomaterials have received increasing attention. However, the biosafety of carbon-based nanomaterials has not been investigated extensively. In this study, we used different types of carbon materials, namely, graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and multiwalled carbon nanotubes (MWCNTs), as models to observe their distribution and oxidative damage in vivo.
The results of Histopathological and ultrastructural examinations indicated that the liver and lungs were the main accumulation targets of these nanomaterials. SR-μ-XRF analysis revealed that SWCNTs and MWCNTs might be present in the brain. This shows that the three types of carbon-based nanomaterials could cross the gas–blood barrier and eventually reach the liver tissue. In addition, SWCNTs and MWCNTs could cross the blood–brain barrier and accumulate in the cerebral cortex. The increase in ROS and MDA levels and the decrease in GSH, SOD, and CAT levels indicated that the three types of nanomaterials might cause oxidative stress in the liver. This suggests that direct instillation of these carbon-based nanomaterials into rats could induce ROS generation. In addition, iron (Fe) contaminants in these nanomaterials were a definite source of free radicals. However, these nanomaterials did not cause obvious damage to the rat brain tissue. The deposition of selenoprotein in the rat brain was found to be related to oxidative stress and Fe deficiency. This information may support the development of secure and reasonable applications of the studied carbon-based nanomaterials.
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-11
Abstract： [Background]:In response to the issue of neutron beam instability or misfire during the operation of the Thorium Molten Salt Reactor with a Particle and Neutron Source (TMSR-PNS), it is necessary to design and develop a neutron beam monitor with high counting rate, low neutron beam perturbation, and high neutron/gamma discrimination capability. [Purpose]: This study aims to investigate the influence of structural parameters of neutron beam monitors on their performance. [Methods]: Firstly, considering that the energy spectrum of TMSR-PNS mainly focuses on the energy range from thermal neutrons to 1 MeV, LiF was chosen as the neutron conversion material. The SRIM program was used to calculate the range of secondary charged particles in the neutron conversion layer and the scintillator, providing a preliminary reference for determining the thickness. Subsequently, a relevant physical model was established using Geant4, irradiating with neutrons and gamma rays of different energies. Finally, the simulation results were used to determine the effects of parameters such as neutron conversion layer thickness, scintillator thickness, metal shell, and the placement angle of the PMT on the detector performance. [Results]: The neutron conversion layer thickness of the scintillator is relatively suitable at about 2 µm for intrinsic detection efficiency. With a scintillator thickness of 2 mm and a discrimination threshold of 0.1 MeV, the detector demonstrates insensitivity to gamma rays. Additionally, by comparing the impact of different shell materials on electron generation by gamma rays, iron, which produces fewer electrons, was selected as the shell material. [Conclusions]: The influence of detector structural parameters on detector performance obtained in this study is of guiding significance, providing theoretical reference for the subsequent preparation of detectors.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-10
Abstract： [Background]: Electron cyclotron resonance heating (ECRH) is an important heating and plasma current control method for the HL-3 tokamak. Microwave inject into plasma through the launcher, which is an important part of the ECRH system. [Purpose]: Design and test the ECRH launcher system of the HL-3 tokamak. [Methods]: Design the transmission path and structure of the launcher. Simulate and calculate the effect of microwave injection. Test the transmission angle and rotation speed of the launcher, and calibrate the rotation angle of the launcher. [Results]: The optical path design of the No. 2 upper launcher has been completed. The full range response time of the equatorial launcher is less than 90ms; The full range response time of the No. 1 upper launcher is less than 190ms. [Conclusions]: The optical path design of the No. 2 upper launcher meets the requirements. The control of the equatorial launcher and the No. 1 upper launcher is precise and fast, meeting the requirements for experimental use of the tokamak.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-10
Abstract： Under high load conditions, the speed regulation system of the feedwater pump and the main/bypass valve regulation system of nuclear power units are coupled, resulting in control system oscillation, which poses a challenge to the reliability and durability of the actuator, and also affects the safe and stable operation of the nuclear power unit. Therefore, it is crucial to solve the coupling oscillation problem of control systems under high load conditions. Through in-depth analysis of the multi base fluctuation curve, it was found that the slow response characteristics of the executing mechanism and the inability to follow the response speed of the control system in a timely manner are the main reasons for the adjustment fluctuation. By evaluating the response characteristic curve of the actuator, optimizing the parameters of the valve actuator, implementing matching settings for proportional gain, speed gain, and minimum loop gain, optimizing the response characteristics in three aspects: good small signal follow-up, low large signal overshoot, and fast time response. And it improve the response and control characteristics of the actuator when it has both small and large signals. By adjusting the characteristics of the actuator, the fluctuation amplitude of the steam generator water level under high load was significantly reduced.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-09
Abstract： [Background]: In neutral beam injectors, the calorimetric target is one of the most important water-cooled components, responsible for receiving and measuring beam power. In addition, by using a built-in thermocouple array, the temperature rise at different positions of the target plate can be monitored in real-time, thereby obtaining the power density distribution of the extracted ion beam or neutral beam. [Purpose]: Develop a calorimetric target for the neutral beam injector in the HL-3 device, which can meet the requirements of target plate lifting and thermal load absorption. [Methods]: The design of the calorimetry target adopts a linear push rod mechanism to achieve lifting and lowering, and adopts a "W" - shaped target plate structure to achieve absorption of neutral beam energy. In addition, the fluid calculation module of Ansys Workbench was used to simulate the temperature distribution of the calorimetry target under full power operation. [Results]: Under full power operating conditions, the deflecting magnet is opened, and the maximum temperature rise of the calorimetry target is 526.4 degrees Celsius, which can be lowered to room temperature within half a minute, meeting the requirements for the use of the beam line. [Conclusions]: Successfully developed a calorimetric target that meets usage requirements.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-05-08
Abstract： Accurate and efficient online parameter identification and state estimation are crucial for leveraging Digital Twin simulations to optimize the operation of near-carbon-free nuclear energy systems. In previous studies, we developed a reactor operation digital twin (RODT). However, non-differentiabilities and discontinuities arise when employing machine-learning-based surrogate forward models, challenging traditional gradient-based in verse methods and their variants. This study investigated deterministic and metaheuristic algorithms and developed hybrid algorithms to address these issues. An efficient modular RODT software framework that incorpo rates these methods into its post-evaluation module is presented for comprehensive comparison. The methods were rigorously assessed based on convergence profiles, stability with respect to noise, and computational performance. The numerical results show that the hybrid KNNLHS algorithm excels in real-time online applications, balancing accuracy and efficiency with a prediction error rate of only 1% and processing times of less than 0.1 s. Contrastingly, algorithms such as FSA, DE, and ADE, although slightly slower (approximately 1s), demonstrated higher accuracy with a 0.3% relative L2 error, which advances RODT methodologies to harness machine learning and system modeling for improved reactor monitoring, systematic diagnosis of off-normal events, and lifetime management strategies. The developed modular software and novel optimization methods presented offer pathways to realize the full potential of RODT for transforming energy engineering practices.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2024-05-08
Abstract： The high level radioactive liquid waste (HLLW) storage building is an essential facility in the spent fuel reprocessing plant. and its stable operation is related to the production safety of the entire plant area. This article elaborates on the process system design of HLLW storage building based on design standards and engineering practice. including the HLLW storage and transportation system. circulating cooling water system. HLLW mixing system. dilution air and exhaust treatment system of the liquid waste storage tank. and so on. The overall layout form. process equipment and pipeline layout characteristics of HLLW storage building are introduced with the example of the actual project. Reference can be provided for designing of HLLW storage building and other nuclear chemical projects in the future.
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2024-05-08
Abstract： In this study, to efficiently remove Pb(II) from aqueous environments, a novel L-serine-modified polyethylene/polypropylene nonwoven fabric sorbent (NWF-serine) was fabricated through the radiation grafting of glycidyl methacrylate and subsequent L-serine modification. The effect of the absorbed dose was investigated in the range of 5–50 kGy. NWF-serine was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Batch adsorption tests were conducted to investigate the influences of pH, adsorption time, temperature, initial concentration, and sorbent dosage on the Pb(II) adsorption performance of NWF-serine. The results indicated that Pb(II) adsorption onto NWF-serine was an endothermic process, following the pseudo-second-order kinetic model and Langmuir isotherm model. The saturated adsorption capacity was 198.1 mg/g. NWF-serine exhibited Pb(II) removal rates of 99.8% for aqueous solutions with initial concentrations of 100 mg/L and 82.1% for landfill leachate containing competitive metal ions such as Cd, Cu, Ni, Mn, and Zn. Furthermore, NWF-serine maintained 86% of its Pb(II) uptake after five use cycles. The coordination of the carboxyl and amino groups with Pb(II) was confirmed using X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis.
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2024-05-08
Abstract： As the main component of low-activation ferrite/martensite steel in candidate materials for fusion reactor, Fe-Cr alloy will enter the material and produce micro-defects under actual working conditions, which will cause radiation damage and affect the radiation resistance and other physical and chemical properties of the material. In this paper, the interface of Fe-Cr alloy, which is the main material of reactor, is simulated by first-principles calculation. He atoms are doped in different gap positions and substitution positions. The formation energy is calculated after structural optimization, and the stability of He atoms in different positions is obtained. At the same time, the calculation of volume shows that the lattice aberration of He at the interstitial position of Fe octahedron near the interface is caused by the hybridization of He, Fe and Cr atoms at specific positions.
Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-07
Abstract： [Background]: With the deepening of oil and gas exploration, the research on the design and measurement methods of X-ray density logging tools, as a new generation of controllable sources, has attracted widespread attention. [Purpose]: Based on the prototype of ultra-slim gamma logging tool, the gamma source is replaced with an X-ray source. [Methods]: The specific content includes: 1) simulating and matching the energy spectrum of the X-ray source; 2) comprehensively guiding the forward design of the key parameters of the tool through indicators such as detection efficiency, formation sensitivity, and detection depth; 3) conducting X-ray density measurements based on the multivariate forward and inverse modeling method, and comparing them with gamma density logging results. [Results]: The results show that when the short and long-spaced detectors’ source distances of the X-ray tool are set to 110mm and 290mm, it can achieve comparable or even higher detection indicators compared to gamma tool. Compared with gamma logging, X-ray logging has better formation sensitivity, vertical resolution, and formation measurement accuracy. The formation density and Pe are within 0.015g/cm3 and 0.2b/e, respectively. Especially in the barite mudcake scenario, the accuracy of Pe measurement has been improved by 47%. [Conclusions]: These studies provide reference for tool forward design and X-ray density measurement.
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