• A novel method for gamma spectrum analysis of low-level and intermediate-level radioactive waste

    分类: 核科学技术 >> 辐射防护技术 提交时间: 2023-06-06

    摘要: The uncertainty of nuclide libraries in the analysis of the gamma spectra of low- and intermediate-level radioactive waste (LILW) using existing methods produces unstable results. To address this problem, a novel spectral analysis method is proposed in this study. In this method, overlapping peaks are located using a continuous wavelet transform. An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks. Combined with the adaptive sensitive nonlinear iterative peak, this method can effectively subtracts the background. Finally, a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library. Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152, a segmented gamma scanning experiment for a 200 L standard drum, and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides (Sb-125, Sb-124, and Cs-134) are conducted. The results of the experiments indicate that (1) the novel method and gamma vision (GV) with an accurate nuclide library have the same spectral analysis capability, and the peak area calculation error is less than 4%; (2) compared with the GV, the analysis results of the novel method are more stable; (3) the novel method can be applied to the activity measurement of LILW, and the error of the activity reconstruction at the equivalent radius is 2.4%; and (4) The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library. This novel method can improve the accuracy and precision of LILW measurements, provide key technical support for the reasonable disposal of LILW, and ensure the safety of humans and the environment.

  • Electromagnetic Fields of Moving Point Sources in the Vacuum

    分类: 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类: 天文学 >> 天文学 提交时间: 2024-05-22

    摘要: The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.

  • On the accuracy and efficiency of the reactor operation digital twin for parameter identification and state estimation

    分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-05-08

    摘要: 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 1 s), 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. 

  • Perhaps We Have Misunderstood the Maxwell’s Theory and the Galilean Transformations

    分类: 信息科学与系统科学 >> 信息科学与系统科学基础学科 分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类: 电子与通信技术 >> 光电子学与激光技术 分类: 物理学 >> 地球物理学、天文学和天体物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2024-04-08

    摘要: The Einstein’s theory of special relativity is based on his two postulates. The first is that the laws of physics are the same in all inertial reference frames. The second is that the velocity of light in the vacuum is the same in all inertial frames. The theory of special relativity is considered to be supported by a large number of experiments. This paper revisits the two postulates according to the new interpretations to the exact solutions of moving sources in the laboratory frame. The exact solutions are obtained using the classic Maxwell’s theory, which clearly show that the propagation velocity of the electromagnetic waves of moving sources in the vacuum is not isotropic; the propagation velocity of the electromagnetic waves and the moving velocity of the sources cannot be added like vectors; the transverse Doppler effect is intrinsically included in the fields of the moving sources. The electromagnetic sources are subject to the Newtonian mechanics, while the electromagnetic fields are subject to the Maxwell’s theory. We argue that since their behaviors are quite different, it is not a best choice to try to bind them together and force them to undergo the same coordinate transformations as a whole, like that in the Lorentz transformations. Furthermore, the Maxwell’s theory does not impose any limitations on the velocity of the electromagnetic waves. To assume that all objects cannot move faster than the light in the vacuum need more examinations. We have carefully checked the main experiment results that were considered as supporting the special relativity. Unfortunately, we found that the experimental results may have been misinterpreted. We here propose a Galilean-Newtonian-Maxwellian relativity, which can give the same or even better explanations to those experimental results.

  • Dynamic evaluation of a scaled-down heat pipe-cooled system during start-up/shut-down processes using a hardware-in-the-loop test approach

    分类: 物理学 >> 核物理学 提交时间: 2023-10-06

    摘要: Micro mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power generators and can be flexibly deployed in remote places to meet increasing electric power demands. However, previous steady-state simulations and experiments have deviated significantly from actual micronuclear system operations. Hence, a transient analysis is required for performance optimization and safety assessment. In this study, a hardware-in-the-loop (HIL) approach was used to investigate the dynamic behavior of scaled-down heat pipe-cooled systems. The real-time features of the HIL architecture were interpreted and validated, and an optimal time step of 500 ms was selected for the thermal transient. The power transient was modeled using point kinetic equations, and a scaled-down thermHeal prototype was set up to avoid modeling unpredictable heat transfer behaviors and feeding temperature samples into the main program running on a desktop PC. A series of dynamic test results showed significant power and temperature oscillations during the transient process, owing to the inconsistency of the rapid nuclear reaction rate and large thermal inertia. The proposed HIL approach is stable and effective for further studying of the dynamic characteristics and control optimization of solid-state small nuclear-powered systems at an early prototyping stage.

  • Semi-empirical and Semi-quantitative Lightweight Shielding Design Algorithm

    分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-06

    摘要: The lightweight shielding design of small reactors is a research hotspot. Based on a small helium-xenon-cooled solid reactor, the effects of thickness and number of shielding layers on the radiation dose are first studied. It is found that when photons are shielded first and the number of shielding layers is odd, the radiation dose can be significantly reduced. To reduce the weight of the shielding body, the relative thickness of the shielding layers is optimized by the genetic algorithm. The optimized scheme can reduce the radiation dose by up to 57% and helps reduce the weight by 11.84%. To determine the total thickness of shielding layers and avoid the local optimal solution, a formula that gives the relationship between the total thickness and the radiation dose is established through large-scale calculations, which has an error of 0.8%~7.45% compared with the Monte Carlo method. A semi-empirical and semi-quantitative lightweight shielding design algorithm is proposed to integrate the above works, and a code SDIC1.0 is developed to achieve the optimized lightweight shielding design for small reactors. It has been verified that the error between SDIC1.0 and Monte Carlo code RMC is about 10%, and the time has increased by 6.3 times.

  • Rapid Diagnosis Method for Transplutonium Isotopes Production in High Flux Reactor

    分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-05-31

    摘要: 本文提出了一种超钚同位素辐照生产过程的快速诊断方法,实现了Pu-238、Cm-242、Cm-244和Cf-252的产量提升。

  • On the transient models of the VITAS code: applications in the C5G7-TD pin-resolved benchmark problem

    分类: 核科学技术 >> 裂变堆工程技术 分类: 核科学技术 >> 核动力工程技术 提交时间: 2023-05-30

  • High-Resolution Neutronics Model for 238Pu Production in High-Flux Reactors

    分类: 核科学技术 >> 同位素技术 提交时间: 2024-04-26

    摘要: We proposed and compared three methods (filter burnup, single-energy burnup, and burnup extremum analysis) to build a high-resolution neutronics model for 238Pu production in high-flux reactors. The filter burnup and single-energy burnup methods have no theoretical approximation and can achieve a spectrum resolution of up to ~1 eV, thereby constructing the importance curve and yield curve of the full energy range. The burnup extreme analysis method combines the importance and yield curves to consider the influence of irradiation time on production efficiency, thereby constructing extreme curves. The three curves, which quantify the transmutation rate of the nuclei in each energy region, are of physical significance because they have similar distributions. A high-resolution neutronics model for 238Pu production was established based on these three curves, and its universality and feasibility were proven. The neutronics model can guide the neutron spectrum optimization and improve the yield of 238Pu by up to 18.81%. The neutronics model revealed the law of nuclei transmutation in all energy regions with high spectrum resolution, thus providing theoretical support for high-flux reactor design and irradiation production of 238Pu

  • Numerical and Theoretical Investigations of Heat Transfer Characteristics in Helium–Xenon Cooled Microreactor Core

    分类: 物理学 >> 核物理学 提交时间: 2023-09-07

    摘要: Heliumxenon cooled microreactors are a vital technological solution for portable nuclear reactor power sources. To examine the convective heat transfer behavior of heliumxenon gas mixtures in a core environment, numerical simulations are conducted on a cylindrical coolant channel and its surrounding solid regions. Validated numerical methods are used to determine the effect and mechanisms of power and its distribution, inlet temperature and velocity, and outlet pressure on the distribution and change trend of the axial Nusselt number. Furthermore, a theoretical framework that can describe the effect of power variation on the evolution of the thermal boundary layer is employed to formulate an axial distribution correlation for the Nusselt number of the coolant channel, under the assumption of a cosine distribution for the axial power. Based on the simulation results, the correlation coefficients are determined, and a semi-empirical relationship is identified under the corresponding operating conditions. The correlation derived in this study is consistent with the simulations, with an average relative error of 5.3% under the operating conditions. Finally, to improve the accuracy of the predictions near the entrance, a segmented correlation is developed by combining the Kays correlation with the aforementioned correlation. The new correlation reduces the average relative error to 2.9% and maintains satisfactory accuracy throughout the entire axial range of the channel, thereby demonstrating its applicability to turbulent heat transfer calculations for heliumxenon gas mixtures within the core environment. These findings provide valuable insights into the convective heat transfer behavior of a heliumxenon gas mixture in a core environment.

  • Development of multi-group Monte-Carlo transport and depletion coupling calculation method and verification with metal-fueled fast reactor

    分类: 核科学技术 >> 核科学与技术 提交时间: 2023-09-06

    摘要: The accurate modeling of depletion, intricately tied to the solution of the neutron transport equation, is crucial for the design, analysis, and licensing of nuclear reactors and their fuel cycles. This paper introduces a novel multi-group Monte-Carlo depletion calculation approach. Multi-group cross-sections (MGXS) are derived from both 3D whole-core modeling and a 2D fuel subassembly using the continuous-energy Monte-Carlo technique. Core calculations employ the multi-group Monte-Carlo method, accommodating both homogeneous and specific local heterogeneous geometries. The proposed method has been validated against the MET-1000 metal-fueled fast reactors, using both the OECD/NEA benchmark and a new refueling benchmark introduced in this paper. Our findings suggest that microscopic MGXS, produced via the Monte-Carlo technique, are viable for fast reactor depletion analyses. Furthermore, the locally heterogeneous model with angular-dependent MGXS offers robust predictions for core reactivity, control rod value, sodium void value, Doppler constants, power distribution, and concentration levels.

  • An efficient parallel algorithm of variational nodal method\\for heterogenous neutron transport problems

    分类: 核科学技术 >> 核科学与技术 提交时间: 2024-02-13

    摘要: The heterogeneous variational nodal method (HVNM) has emerged as a potential approach for solving high-fidelity neutron transport problems. However, achieving accurate results with HVNM in large-scale problems using high-fidelity models has been challenging due to the prohibitive computational costs. This paper presents an efficient parallel algorithm tailored for HVNM based on the Message Passing Interface standard. The algorithm evenly distributes the response matrix sets among processors during the matrix formation process, thus enabling independent construction without communication. Once the formation tasks are completed, a collective operation merges and shares the matrix sets among the processors. For the solution process, the problem domain is decomposed into subdomains assigned to specific processors, and the red-black Gauss-Seidel iteration is employed within each subdomain to solve the response matrix equation. Point-to-point communication is conducted between adjacent subdomains to exchange data along the boundaries. The accuracy and efficiency of the parallel algorithm are verified using the KAIST and JRR-3 test cases. Numerical results obtained with multiple processors agree well with those obtained from Monte Carlo calculations. The parallelization of HVNM results in eigenvalue errors of 31 pcm/-90 pcm and fission rate RMS errors of 1.22%/0.66%, respectively, for the 3D KAIST problem and the 3D JRR-3 problem. In addition, the parallel algorithm significantly reduces computation time, with an efficiency of 68.51% using 36 processors in the KAIST problem and 77.14% using 144 processors in the JRR-3 problem.

  • GA-based dynamical correction of dispersion coefficients in Lagrangian puff model

    分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》

    摘要: In atmospheric dispersion models of nuclear accident, the dispersion coefficients were usually obtained by tracer experiment, which are constant in different atmospheric stability classifications. In fact, the atmospheric wind field is complex and unstable. The dispersion coefficients change even in the same atmospheric stability, hence the great errors brought in. According to the regulation, the air concentration of nuclides around nuclear power plant should be monitored during an accident. The monitoring data can be used to correct dispersion coefficients dynamically. The error can be minimized by correcting the coefficients. This reverse problem is nonlinear and sensitive to initial value. The property of searching the optimal solution of Genetic Algorithm (GA) is suitable for complex high-dimensional situation. In this paper, coupling with Lagrange dispersion model, GA is used to estimate the coefficients. The simulation results show that GA scheme performs well when the error is big. When the correcting process is used in the experiment data, the GA-estimated results are numerical instable. The success rate of estimation is 5% lower than the one without correction. Taking into account the continuity of the dispersion coefficient, Savitzky-Golay filter is used to smooth the estimated parameters. The success rate of estimation increases to 75.86%. This method can improve the accuracy of atmospheric dispersion simulation.

  • Adsorption behaviors of iodide anion on silver loaded macroporous silicas

    分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》

    摘要: A macroporous silica-based silver loaded adsorbent was synthesized by grafting the silver complexes of thiourea (Ag(tu)3NO3) into a silica-based copolymer support (SiO2-P). The adsorbent was used to uptake iodide anions (I-) by batch and column techniques. The kinetic and saturated adsorption experiments were carried out by varying the shaking times and initial concentration of I-. The experiments found that the kinetic adsorption of I- was controlled by a pseudo second order model and the saturated adsorption of I- was controlled by the chemisorption mechanism, which followed a Langmuir adsorption equation. The breakthrough curve of I- had a S-shaped profile. The column efficiency was estimated to be over 90%.

  • Electrolytic reduction of Re(VII) using a flow type electrolysis cell and its possibility of radiopharmaceuticals application

    分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》

    摘要: The electrochemical properties of perrhenate were studied in hydrochloric acid solution via cyclic voltammetry by disk glassy carbon electrode. The electroreduction of perrhenate was performed at a constant potential -0.33 V (vs. Ag/AgCl) with a potentiostat by a flow type electrolysis cell. It was found that the change of rhenium ion concentration before and after electrolysis was negligible. This means almost no rhenium or rhenium oxides were deposited on the carbon fiber electrode during the electroreduction. The rhenium ion solution changed from colorless into yellow-brown after electrolysis process. UV-Visible spectrophotometry was used to characterize the oxidation states of Re before and after electrolysis. Some obvious peaks were detected after electrolysis, indicating that Re(VII) was reduced to Re(V). The complex behavior and stability of Re(V)-HEDP were discussed for the purpose of electroreduction of Re(VII) or Tc(VII) on radiopharmaceuticals production.

  • Adsorption behavior of Zr(IV) and Hf(IV) on a silica-based macroporous TODGA adsorbent

    分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》

    摘要: In order to separate Zr(IV) and Hf(IV) in acidic solution, several kinds of silica-based macroporous adsorbents were synthesized. Their adsorption selectivity for Zr(IV) and Hf(IV) in HCl solution was investigated, and the TODGA adsorbent for the two elements had the largest adsorption difference. The effects of acid type, HCl concentration, and temperature on the adsorption behavior of Zr(IV) and Hf(IV) onto the TODGA adsorbent were conducted by batch experiments. It was found that H+ exhibited a quite strong influence on adsorption capacity of Zr(IV) and Hf(IV). Isotherm fitting showed that the Langmuir model agrees well with the experimental data. The thermodynamic parameters indicate that the adsorption processes for both elements are endothermic reactions. The TODGA adsorbent had the higher adsorption selectivity for Zr(IV) over Hf(IV) and could be promising for their mutual separation.

  • Ensemble Bayesian Method for Parameter Distribution Inference: Application to Reactor Physics

    分类: 物理学 >> 核物理学 提交时间: 2023-11-18

    摘要: The estimation of model parameters is an important subject in engineering. In this area of work, the prevailing approach is to estimate or calculate these as deterministic parameters. In this study, we consider the model parameters from the perspective of random variables and describe the general form of the parameter distribution inference problem. Under this framework, we propose an ensemble Bayesian method by introducing Bayesian inference and the Markov chain Monte Carlo (MCMC) method. Experiments on a finite cylindrical reactor and a 2D IAEA benchmark problem show that the proposed method converges quickly and can estimate parameters effectively, even for several correlated parameters simultaneously. Our experiments include cases of engineering software calls, demonstrating that the method can be applied to engineering, such as nuclear reactor engineering.

  • Anisotropic propagation speed of light on rotating Earth's surface - theoretical derivation, implications for definition of meter, and crucial experiment

    分类: 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 提交时间: 2023-07-05

    摘要: Whether the speed of light at the surface of rotating Earth is isotropic or not is both an important theoretical problem and one that has significant implications for scientific practices. Especially the unit of length, a meter, is defined as the length of the path travelled by light in vacuum in 1/299792458 of a second, on the basis that the speed of light is constant, c = 299792458 m/s. By applying the GPS range equation whose correctness has been fully verified by GPS practices, we found that the speed of light on rotating Earth's surface is neither constant nor isotropic, but    rE c' c v d , where rE v is the local linear velocity of Earth's rotation, and d is the unit vector of the light propagation's direction. It follows that the anisotropy of the speed of light at the Earth's surface has a significant impact on the definition of the meter. For example, at the equator, in 1/299792458 of a second the length of the eastward light path is 3.1 m shorter than the westward one's. Based on this, and the difference between Earth rotation's Sagnac effects on the equator and the meridian, we propose a crucial experiment to examine the anisotropy of the speed of light: let a stable pulsed laser emitting pulses in two opposite directions, use the ultrafast imaging techniques for visualizing, measuring and comparing the spacing of the pulses in opposite directions. Then we can decisively conclude whether the speed of light is anisotropic or not.

  • Extraction of lanthanides from nitric acid solution using isobutyl-BTP/ionic liquid system

    分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》

    摘要: Extraction behavior of lanthanides (La, Eu, Dy, Lu) from HNO3 solution was studied using a novel extraction system with hydrophobic ionic liquid being diluent and isobutyl-BTP being extractant. Compared with that in isobutyl-BTP/cyclohexane extraction system, application of ionic liquid as the extracting phase provided unprecedented enhancement of the extraction performance of isobutyl-BTP for lanthanides. It was found that the isobutyl-BTP/[Cnmim][NTf2] extraction system is favorable to get good extraction at low acidity condition (isobutyl-BTP/ [Cnmim][NTf2] (n=2, 6, 8) systems, isobutyl-BTP/[C2mim][NTf2] extraction system provides the best extraction performance and fastest extraction kinetics within 5 min towards Dy3+. The extraction is spontaneous endothermic and temperature is good for extraction. The transfer of lanthanides, in isobutyl-BTP/[C2mim][NTf2] extraction system, proceeded via a cation exchange mechanism, in contrast to extraction of neutral complex in the cyclohexane system.

  • Dissection of mechanisms of Chinese medicinal formula Realgar-Indigo naturalis as an effective treatment for promyelocytic leukemia

    分类: 生物学 >> 生物医药 提交时间: 2017-05-10

    摘要: To enhance therapeutic efficacy and reduce adverse effects, practitioners of traditional Chinese medicine (TCM) prescribe a combination of plant species/minerals, called formulae, based on clinical experience. Nearly 100,000 formulae have been recorded, but the working mechanisms of most remain unknown. In trying to address the possible beneficial effects of formulae with current biomedical approaches, we use Realgar-Indigo naturalis formula (RIF), which has been proven to be very effective in treating human acute promyelocytic leukemia (APL) as a model. The main components of RIF are realgar, Indigo naturalis, and Salvia miltiorrhiza, with tetraarsenic tetrasulfide (A), indirubin (I), and tanshinone IIA (T) as major active ingredients, respectively. Here, we report that the ATI combination yields synergy in the treatment of a murine APL model in vivo and in the induction of APL cell differentiation in vitro. ATI causes intensified ubiquitination/degradation of promyelocytic leukemia (PML)-retinoic acid receptor #1; (RAR#1;) oncoprotein, stronger reprogramming of myeloid differentiation regulators, and enhanced G1/G0 arrest in APL cells through hitting multiple targets compared with the effects of mono- or biagents. Furthermore, ATI intensifies the expression of Aquaglyceroporin 9 and facilitates the transportation of A into APL cells, which in turn enhances A-mediated PML-RAR#1; degradation and therapeutic efficacy. Our data also indicate A as the principal component of the formula, whereas T and I serve as adjuvant ingredients. We therefore suggest that dissecting the mode of action of clinically effective formulae at the molecular, cellular, and organism levels may be a good strategy in exploring the value of traditional medicine.