Preparation and Properties of the Fast-Curing γ-Ray-Shielding Materials Based on Polyurethane

Minxuan Ni,Xiaobin Tang,Hao Chai,Yun Zhang,Tuo Chen,Da Chen 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.6

In this study, fast-curing shielding materials were prepared with a two-component polyurethane matrix and a filler material of PbO through a one-step, laboratory-scale method. With an increase in the filler content, viscosity increased. However, the two components showed a small difference. Curing time decreased as the filler content increased. The minimum tack-free time of 27 s was obtained at a filler content of 70 wt%. Tensile strength and compressive strength initially increased and then decreased as the filler content increased. Even when the filler content reached 60 wt%, mechanical properties were still greater than those of the matrix. Cohesional strength decreased as the filler content increased. However, cohesional strength was still greater than 100 kPa at a filler content of 60 wt%. The γ-ray-shielding properties increased with the increase in the filler content, and composite thickness could be increased to improve the shielding performance when the energy of γ-rays was high. When the filler content was 60 wt%, the composite showed excellent comprehensive properties.

Low-noise reconstruction method for coded-aperture gamma camera based on multi-layer perceptron

Rui Zhang,Xiaobin Tang,Pin Gong,Peng Wang,Cheng zhou,Xiaoxiang Zhu,Dajian Liang,Zeyu Wang 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Accurate localization of radioactive materials is crucial in homeland security and radiological emergencies. Coded-aperture gamma camera is an interesting solution for such applications and can be developed into portable real-time imaging devices. However, traditional reconstruction methods cannot effectively deal with signal-independent noise, thereby hindering low-noise real-time imaging. In this study, a novel reconstruction method with excellent noise-suppression capability based on a multi-layer perceptron (MLP) is proposed. A coded-aperture gamma camera based on pixel detector and coded-aperture mask was constructed, and the process of radioactive source imaging was simulated. Results showed that the MLP method performs better in noise suppression than the traditional correlation analysis method. When the Co-57 source with an activity of 1 MBq was at 289 different positions within the field of view which correspond to 289 different pixels in the reconstructed image, the average contrast-to-noise ratio (CNR) obtained by the MLP method was 21.82, whereas that obtained by the correlation analysis method was 5.85. The variance in CNR of the MLP method is larger than that of correlation analysis, which means the MLP method has some instability in certain conditions.

Power Decoupling Method for Single Phase Differential Buck Converter

Wenli Yao,Yi Tang,Xiaobin Zhang,Xiongfei Wang,Poh Chiang Loh,Frede Blaabjerg 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The well-known inherent second-order ripple power in single phase converters imposes harmonic stress on the dc link, resulting in low efficiency and overheating issues. In order to avoid installing bulky electrolytic capacitors or LC filters in the dc-link, this paper presents a differential buck inverter to improve the dc link power quality, and an improved active power decoupling method is proposed to achieve ripple power reduction for both AC-DC and DC-AC conversions. The ripple energy storage is realized by the filter capacitors, which are connected between the output terminal and the negative dc bus. By properly controlling the differential mode voltage of the capacitors, it is possible to transfer desired energy between the DC port and AC port. The common mode voltage is controlled in such a way that the ripple power on the dc side will be reduced. Furthermore, an autonomous reference generation technique is proposed to provide accurate ripple power compensation, and closed-loop controllers are also designed based on small signal models. The effectiveness of this power decoupling method is verified by detailed simulation studies as well as laboratory prototype experimental results.

Metabolite profiles of ginsenosides Rk1 and Rg5 in zebrafish using ultraperformance liquid chromatography/quadrupole-time-of-flight MS

Shen, Wenwen,Wei, Yingjie,Tang, Daoquan,Jia, Xiaobin,Chen, Bin The Korean Society of Ginseng 2017 Journal of Ginseng Research Vol.41 No.1

Background: In the present study, metabolite profiles of ginsenosides Rk1 and Rg5 from red ginseng or red notoginseng in zebrafish were qualitatively analyzed with ultraperformance liquid chromatography/quadrupole-time-of-flight MS, and the possible metabolic were pathways proposed. Methods: After exposing to zebrafish for 24 h, we determined the metabolites of ginsenosides Rk1 and Rg5. The chromatography was accomplished on UPLC BEH C18 column using a binary gradient elution of 0.1% formic acetonitrile-0.1% formic acid water. The quasimolecular ions of compounds were analyzed in the negative mode. With reference to quasimolecular ions and MS2 spectra, by comparing with reference standards and matching the empirical molecular formula with that of known published compounds, and then the potential structures of metabolites of ginsenosides Rk1 and Rg5 were acquired. Results: Four and seven metabolites of ginsenoside Rk1 and ginsenoside Rg5, respectively, were identified in zebrafish. The mechanisms involved were further deduced to be desugarization, glucuronidation, sulfation, and dehydroxymethylation pathways. Dehydroxylation and loss of C-17 residue were also metabolic pathways of ginsenoside Rg5 in zebrafish. Conclusion: Loss of glucose at position C-3 and glucuronidation at position C-12 in zebrafish were regarded as the primary physiological processes of ginsenosides Rk1 and Rg5.

Preparation and characteristics of a flexible neutron and g-ray shielding and radiation-resistant material reinforced by benzophenone

Pin Gong,Minxuan Ni,Hao Chai,Feida Chen,Xiaobin Tang 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.3

With a highly functional methyl vinyl silicone rubber (VMQ) matrix and filler materials of B4C, PbO, andbenzophenone (BP) and through powder surface modification, silicone rubber mixing, and vulcanizedmolding, a flexible radiation shielding and resistant composite was prepared in the study. The dispersionproperty of the powder in the matrix filler was improved by powder surface modification. BP was addedinto the matrix to enhance the radiation resistance performance of the composites. After irradiation, thetensile strength, elongation, and tear strength of the composites decreased, while the Shore hardness ofthe composites and the crosslinking density of the VMQ matrix increased. Moreover, the compositeswith BP showed better mechanical properties and smaller crosslinking density than those without BPafter irradiation. The initial degradation temperatures of the composites containing BP before and afterirradiation were 323.6 C and 335.3 C, respectively. The transmission of neutrons for a 2-mm thicksample was only 0.12 for an AmeBe neutron source. The transmission of g-rays with energies of 0.662,1.173, and 1.332 MeV for 2-cm thick samples were 0.7, 0.782, and 0.795, respectively

Neutron-irradiated effect on the thermoelectric properties of Bi2Te3-based thermoelectric leg

Zhao Huanyu,Liu Kai,Xu Zhiheng,Liu Yunpeng,Tang Xiaobin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 1010 and 1 1013 n/cm2 by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi2Te2.7Se0.3 and ptype Bi0.5Sb1.5Te3 thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi2Te2.7Se0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

Health monitoring of carbon fiber-reinforced polymer composites in γ-radiation environment using embedded fiber Bragg grating sensors

Zhong Jing,Chen Feida,Rui Yuehao,Li Yong,Tang Xiaobin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Fiber-reinforced polymer (FRP) composites are considered suitable candidates for structural materials of spacecrafts due to their excellent properties of high strength, light weight, and corrosion resistance. An online health monitoring method for FRP composites must be applied to space structures. However, the application of existing health monitoring methods to space structures is limited due to the harsh space environment. Here, carbon fiber-reinforced polymer (CFRP) composites embedded with fiber Bragg grating (FBG) sensors were prepared to explore the feasibility of strain monitoring using embedded FBG sensors in g-radiation environment. The analysis of the influence of radiation on the strain monitoring demonstrated that the embedded FBG can be successfully applied to the health monitoring of FRP composites in radiation environment.

Conceptual design of a dual drum-controlled space molten salt reactor (D² -SMSR): Neutron physics and thermal hydraulics

Yongnian Song,Nailiang Zhuang,Hangbin Zhao,Chen Ji,Haoyue Deng,Xiaobin Tang Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.