Subjects: Nuclear Science and Technology >> Nuclear Detection Technology and Nuclear Electronics submitted time 2024-05-21
Abstract： [Background]: In order to apply in different scenarios of silicon-photomultiplier-coupled scintillator detector, Preamplifiers need to fulfill different requirements. [Purpose]: This study aims to design high-bandwidth, low-noise preamplifiers to cater for different output modes of silicon-photomultiplier-coupled scintillator detector. [Methods]: Based on OPA855 and consideration of bandwidth and noise, a transimpedance amplifier (TIA) and a voltage feedback amplifier (VFB) were designed. The amplifier circuits were simulated and analysed using PSpice for TI software to obtain circuit parameters. Finally, the signal response and noise baseline level were measured, and signals of 241Am source were analysed using a silicon-photomultiplier-coupled Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG(Ce)) detector. [Results and Conclusions]: These preamplifiers have good gain stability. TIA's bandwidth is 101MHz lower than VFB's 381MHz, but its baseline noise level σnoise≅ 448.32μV is better than the VFB's σnoise≅ 680.96μV . In addition, TIA is suitable for energy measurements and small-area SiPM applications, while VFB is more suitable for time measurements and large-area SiPM arrays.
Subjects: Physics >> Nuclear Physics submitted time 2024-05-20
Abstract： Background : The molten salt pump is one of the main equipment in the thorium based molten salt reactor circuit system, responsible for driving the circulation of molten salt in the circuit. The safety and economy of reactor operation are influenced by the safety and reliability of molten salt pump operation. State monitoring is one of the effective methods to ensure the safe operation of the system. Purpose : In order to detect abnormalities in equipment and system operation timely and provide a basis for condition based maintenance, a study was conducted on the state monitoring and abnormal signal localization of the molten salt pump system. Methods :A desktop application for the real-time monitoring system of molten salt pumps was developed based on the Windows Presentation Foundation (WPF) and Model-View-ViewModel(MVVM). The system is consisted of modules such as monitoring model management, real-time monitoring and alarm, abnormal signal localization, and log query. Results : The relevant operating parameters of the molten salt pump system can be centrally monitored by the system, and the current operating status of the equipment can be displayed in real-time. Signal parameters that may cause abnormalities can be quickly provided after the abnormality occurred. Conclusions : The necessary operational information can be provided by the system for operators. The system is helpful for operators to make operational decisions. Compared to traditional DCS threshold alarms, the timeliness and effectiveness of monitoring have been improved. The foundation for the subsequent application implementation of intelligent operation support is laid.
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 >> 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 >> Engineering Technology of Fission Reactor submitted time 2024-04-07
Abstract： Background : For high-fidelity simulations of fluid dynamics in molten salt reactor, even though a supercomputer is able to suppress the period of each simulation, the consequent expense is still prohibitively costly. A possible way to overcome this limitation is the use of Reduced Order Modelling (ROM) techniques. Purpose : Evaluating the accuracy of the ROM methods for reconstructing the velocity and pressure fields. Methods : Two ROM methods based on the Proper Orthogonal Decomposition (POD) with both Galerkin projection, namely FV-ROM (ROM based on Finite Volume approximation ) and SUP-ROM (ROM with supremizer stabilization ), are established for fluid dynamics of molten salt reactor. Then, both methods are tested on the unsteady cases of liquid-fueled molten salt reactor (LFMSR). Results : The FV-ROM demonstrates notable advantages in both velocity prediction and computational efficiency. For laminar and turbulent transient simulations, the average velocity L2 relative errors are less than 0.5% and 0.6%, respectively, with acceleration ratios of approximately 1500 and 1000 times for single time steps. Conversely, the SUP-ROM scheme demonstrates significant prowess in pressure prediction, achieving remarkably low pressure average L2 relative errors of 0.20% and 0.38% for laminar and turbulent transient scenario, respectively. Conclusions : The integration of the SUP-ROM and FV-ROM for fluid dynamics computations of molten salt reactor could significantly enhances computational efficiency and ensure reliability and accuracy of transient simulation.
Subjects: Physics >> Nuclear Physics submitted time 2024-01-09
J. Hu
Z.Y. Han
Y.J. Li
Z.H. Li
G. Lian
Y.P. Shen
S.Q. Yan
S. Zeng
B. Guo
W.P. Liu
Z. Bai
B.L. Jia
S.L. Jin
J.B. Ma
P. Ma
S.B. Ma
S.W. Xu
Y.Y. Yang
N.T. Zhang
X.D. Tang
Abstract： In Orgueil meteorites, an exceptionally high 22Ne/20Ne abundance ratio or even nearly pure 22Ne is ob#2;served, which is the so-called Ne extraordinary problem. Fossil material of extinct 22Na is believed to be the origin of extraordinary 22Ne, these 22Na nuclides were trapped in grains and incorporated into meteorites in stellar explo#2;sive event. Supernovae and neon-rich novae are the primary events, which are responsible for the production of 22Na through the explosive hydrogen burning process. 22Na(p, γ)23Mg and 19Ne(α, p) 22Na are two crucial reactions in the so-called NeNa-MgAl cycle and the rapid-proton process, which lead to the fast nucleosynthesis up to A=100 nuclide region and the outburst of novae and X-ray bursters. Since many proton resonance levels in odd-A compound nucleus 23Mg may be involved at nova temperature, existing measurements can only provide partial effective information on the 22Na(p, γ)23Mg reaction. Large uncertainties still exist in the astrophysical reaction rates of the two reactions at present. Thick target inverse kinematics method is a very effective way to scan the 23Mg proton resonance levels re#2;lated to the 22Na(p, γ)23Mg reaction via the excitation function of 22Na(p, p) elastic scattering, which could be obtained over a large energy range in one-shot measurement with low-intensity radioactive 22Na beam. In the present work, 22Na+p resonance scattering via thick target inverse kinematics was studied at RIBLL1 radioactive beam line in the HIRFL national laboratory at Lanzhou. A high-purity 22Na beam with an intensity of about 2 × 105 pps was produced via the 1H(22Ne,22Na)n reaction with an alcohol-cooled hydrogen gas target. Time-of-Flight by two plastic scintillator detectors and two parallel-plate avalanche counters were used to monitor the 22Na secondary beam before reaching the (CH2 )n target. The timing information is useful for beam particle identification and the position information is essen#2;tial for 22Na(p,p) elastic scattering kinematics reconstruction. Light recoil particles from 22Na+p reaction system were detected by two sets of double-sided silicon strip detector telescopes centered at 𝜃lab = 0° and 14°, respectively, while the heavy recoil particles were stopped in the (CH2 )n thick target. Two-body kinematics reconstruction of 22Na(p,p) elastic scattering is performed on the event-by-event basis, and an excitation function of 22Na(p,p) is obtained in the energy range of 𝐸c.m. = 1.5 to 4 MeV. Obvious proton resonance structure is observed in the 23Mg compound nucleus, which will be further analyzed with R-matrix nuclear theoretical model.
Subjects: Nuclear Science and Technology >> Nuclear Science and Technology submitted time 2023-06-21
Abstract： Molten salt reactor, as one of the important reactor types of the fourth generation advanced reactor, uses high boiling point molten salt as nuclear fuel, thus having the characteristics of high temperature output and normal pressure operation. The heat pipe molten salt reactor based on thermoelectric power generation has the advantages of molten salt reactor, heat pipe and thermoelectric power generation, that is, high output temperature, high thermoelectric conversion efficiency, simple structure, safety and reliability. Therefore, the reactor has great advantages in the field of energy system, which is an ideal energy source for outer space and deep-sea exploration missions. However, the dense arrangement of heat pipes due to the low thermal conductivity of molten salt in the core brings difficulties to the heat transfer design of thermal power generation in the condensing section of heat pipes. According to the design requirements of the reactor, this paper proposes a heat pipe-thermal power generation coupling system structure suitable for molten salt reactors and conducts heat transfer analysis. The condensing section of the core heat pipe is designed with the tower thermoelectric power generation system. There is a thermoelectric generator between the outer wall of the hot side tower and the inner wall of the cold side tower, and the gap between the generator is made of insulating material to reduce heat leakage. The heat transfer simulation of the four-layer tower thermoelectric power generation system suitable for the heat pipe molten salt reactor was carried out by Ansys Workbench. The analysis shows that when the system is running, the temperature distribution of the overall tower is uniform, the effective heat utilization rate is more than 96%, the system leakage heat is less than 4%, and the temperature difference between the two sides of the generator is greater than 490℃, which is conducive to improving the thermoelectric conversion efficiency. The design is feasible, which is conducive to promoting the application of thermoelectric power generation in the heat pipe molten salt reactor.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The ocean is essential to country’s strategic interests and common destiny of mankind, and therefore equipment of various kinds is urgently needed for all-around and multi-dimensional ocean observation and exploration. This article brief introduced the two technological approaches of nuclear energy supply for underwater observation and exploration equipment and relevant exchange technologies of nuclear heat to electric power, quantitatively summarized the applicability of nuclear energy supply on all kinds of equipment, discussed the nuclear safety issues thereon, and then recommended that the technology research of radioisotope fabrication and separation and the construction of relevant facility, the development of individual reactor and the construction of relevant common facility, the technology research of thermoelectric conversion, and the research of relevant nuclear safety issues, should be special supported.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： Nuclear energy is essential for energy supply and national security. Compared with hydropower, optoelectronics, and wind power, as the clean energy replacing fossil fuels in the future, nuclear power takes great advantage in technology maturity, economical efficiency, as well as sustainability and natural environment flexibility. Come so far, except for a few reactors used for district heating and seawater desalination, nuclear energy is mainly used for power generation. With the development of technology, especially the gradually matured and applied fourth-generation nuclear energy system, nuclear energy is expected for a comprehensive utilization in different areas. This paper elaborates the current status and future development trend of nuclear energy utilization from the highefficient power generation, high-temperature steam electrolysis, water desalination, district heating, and high-temperature industry process. Finally, it is expected that in the near future nuclear energy will occupy an important position in the hybrid-energy system.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： As one of the most promising next generation reactors, the molten salt breeder reactor (MSBR) with excellent inherence security has attracted more and more attentions in recent years due to energy shortage and the security problem of traditional nuclear reactor. The most significant service characteristic of the structural material used in MSBR is the existence of FLiNaK molten salt compared with other nuclear reactors. FLiNaK molten salt is very corrosive to the structural material in the reactor, and affects the safety operation of nuclear power plants. A polycrystalline Ni-Mo-Cr-Fe superalloy was developed and used as an important structural material in MSBR at Oak Ridge National Laboratory (ORNL), but the corrosion mechanism of the alloy in FLiNaK molten salt has not been determined since the study terminated in 1970' s as some politic reasons. Alloy served in harsh environments, often using protective coating to improve the corrosion properties. While few works about the coating corrosion resistance in FLiNaK molten salt were reported at present. Al2O3 and Cr2O3 coatings usually have excellent corrosion resistance in molten salt, such as sulphate, nitrate and halide molten salt. But, whether the oxide film has corrosion resistance in FLiNaK molten salt has not been determined. In this work, the corrosion mechanism of alloy in FLiNaK molten salt was studied by using immersion corrosion experiment through the method of SEM, EDS and XRD. The influence of Al2O3 coating on corrosion resistance in FLiNaK molten salt was also investigated. The results show that the Al2O3 coating does not affect the exsolution corrosion characteristics of Cr and Mo elements in FLiNaK molten salt at 700 ℃ for 400 h. The different is that naked alloy exhibits intergranular corrosion characteristic, and the alloy with Al2O3 coating exhibits spot corrosion characteristic. The Al2O3 coating cannot improve the corrosion resistance of the alloy in FLiNaK molten salt. The Al2O3 film dissolved in molten salt and resulted in the exposure of the alloy surface. The corrosion rate was increased since the formation of corrosion cell between oxide film and the exposed alloy surface.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： The effect of extensometer induced cold-tesile deformation on microstructure and mechanical properties of Ni-based high temperature alloy GH3535 were investigated by means of OM and TEM as well as measurement of true stress-true stain curves. It was found that GH3535 alloy shows characteristics of strong work hardening; cold deformation can result in significant increase of its strength and hardness, whereas decrease of its ductility. With the increase of deformation degree grains were elongated along the deformation direction and twins became profusely lager. The work hardening kinetics of GH3535 alloy is constant with Ludwigson model, dislocation slipping and twin are the main deformation mechanism. With the increase of deformation degree the slip behavior of dislocations changes from single slip to cross slip. When the deformation degree below 30% the work hardening is mainly caused by the dislocation long-range stress field and twin, conversely, for the deformation degree above 30% work hardening is mainly caused by the dislocation short-range stress field and deformation twin.
Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract：介绍了聚焦太阳能热发电中熔融盐应用概况和腐蚀问题，综述了熔融硝酸盐、碳酸盐、氯盐、氟盐、氢氧化物等几种太阳能热发电传热储热候选熔盐腐蚀研究现状与进展，讨论了太阳能领域熔盐腐蚀研究存在的主要问题及进一步的研究方向。
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