• Title/Summary/Keyword: Neutron density

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Microstructure and Mechanical Property of Irradiated Zr-2.5Nb Pressure Tube in Wolsong Unit-1

  • 김영숙;안상복;오동준;김성수;정용무
    • Transactions of Materials Processing
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    • v.8 no.3
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    • pp.241-241
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    • 1999
  • With the aim of assessing the degradation of Zr-2.5Nb pressure tubes operating in the Wolsong unit-1 nuclear power plant, characterization tests are being conducted on irradiated Zr-2.5Nb tubes removed after 10-year operation. The examined tube had been exposed to temperatures ranging from 264 to 306℃ and a neutron fluence of 8.9×$10^{21}$ n/cm²(E>1 MeV) at the maximum. Tensile tests were carried out at temperatures ranging from RT to 300℃. The density of a-type and c-type dislocations was examined on the irradiated Zr-2.5Nb tube using a transmission electron microscope. Neutron irradiation up to 8.9×$10^{21}$ n/cm²(E>1 MeV) yielded an increase in a-type dislocation density of the Zr-2.5Nb pressure tube to 7.5×$10^{14} m^{-2}$, which was highest at the inlet of the tube exposed to the low temperature of 275℃. In contrast, the c-component dislocation density did not change with irradiation, keeping an initial dislocation density of 0.8×$10^{14} m^{-2}$ over the whole length of the tube. As expected, the neutron irradiation increased mechanical strength by about 17-26% in the transverse direction and by 34-39% in the longitudinal direction compared to that of the unirradiated tube at 300℃. The change in the mechanical properties with irradiation is discussed in association with the microstructural change as a function of temperature and neutron fluence.

A Study On Hardware Design for High Speed High Precision Neutron Measurement (고속 고정밀 중성자 측정을 위한 하드웨어 설계에 관한 연구)

  • Jang, Kyeong-Uk;Lee, Joo-Hyun;Lee, Seung-Ho
    • Journal of IKEEE
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    • v.20 no.1
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    • pp.61-67
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    • 2016
  • In this paper, a hardware design method is proposed for high speed high precision neutron radiation measurements. Our system is fabricated to use a high performance A/D Converter for digital data conversion of high precision and high speed analog signals. Using a neutron sensor, incident neutron radiation particles are detected; a precision microcurrent measurement module is also included: this module allows for more precise and rapid neutron radiation measurement design. The high speed high precision neutron measurement hardware system is composed of the neutron sensor, variable high voltage generator, microcurrent precision measurement component, embedded system, and display screen. The neutron sensor detects neutron radiation using high density polyethylene. The variable high voltage generator functions as a 0 ~ 2KV variable high voltage generator that is robust against heat and noise; this generator allows the neutron sensor to perform normally. The microcurrent precision measurement component employs a high performance A/D Converter to precisely and swiftly measure the high precision high speed microcurrent signal from the neutron sensor and to convert this analog signal into a digital one. The embedded system component performs multiple functions including neutron radiation measurement for high speed high precision neutron measurements, variable high voltage generator control, wired and wireless communications control, and data recording. Experiments using the proposed high speed high precision neutron measurement hardware shows that the hardware exhibits superior performance compared to that of conventional equipment with regard to measurement uncertainty, neutron measurement rate, accuracy, and neutron measurement range.

Enhancement of the Critical Current Density of $MgB_2$ Prepared using Mechanically Milled and Glycerin Treated Boron Powder (기계적 밀링 및 글리세린 처리된 보론 분말을 사용하여 제조된 $MgB_2$의 임계전류밀도 향상)

  • Jun, Byung-Hyuk;Kim, Yi-Jeong;Kim, Chan-Joong
    • Progress in Superconductivity
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    • v.10 no.1
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    • pp.40-44
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    • 2008
  • A combined process of a mechanical ball milling and liquid glycerin ($C_{3}H_{8}O_3$) treatment of boron (B) powder has been conducted to enhance the superconducting properties of $MgB_2$. The individual aims of the mechanical milling and the glycerin treatment were to reduce the grain size of the $MgB_2$ and to achieve homogeneous carbon (C) incorporation into the $MgB_2$, respectively. Four kinds of B powders of as-received, glycerin treated, 2 h milled, and 2 h milled + glycerin treated were prepared. $MgB_2$ bulks were fabricated by in situ process using the prepared B powders. The mechanical ball milling was effective for a grain refinement, and a lattice disorder was easily achieved by glycerin addition. It was found that the critical current density ($J_c$) values were enhanced in the samples with milled B or glycerin treated B only. In the $MgB_2$ bulk prepared with both milled and glycerin treated B, the $J_c$ was further increased due to a higher grain boundary density and a greater C substitution.

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Structural and component characterization of the B4C neutron conversion layer deposited by magnetron sputtering

  • Jingtao Zhu;Yang Liu;Jianrong Zhou;Zehua Yang;Hangyu Zhu;Xiaojuan Zhou;Jinhao Tan;Mingqi Cui;Zhijia Sun
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3121-3125
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    • 2023
  • Neutron conversion detectors that use 10B-enriched boron carbide are feasible alternatives to 3He-based detectors. We prepared boron carbide films at micron-scale thickness using direct-current magnetron sputtering. The structural characteristics of natural B4C films, including density, roughness, crystallization, and purity, were analyzed using grazing incidence X-ray reflectivity, X-ray diffraction, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and scanning electron microscopy. A beam profile test was conducted to verify the practicality of the 10B-enriched B4C neutron conversion layer. A clear profile indicated the high quality of the neutron conversion of the boron carbide layer.

저형상비 토카막 중성자원에 기반한 핵변환로 형상 연구

  • Hong, Bong-Geun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.414.2-414.2
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    • 2016
  • The optimal configuration of a transmutation reactor based on a low aspect ratio tokamak is determined using coupled analysis of tokamak systems and neutron transport. The inboard radial build of the reactor components is obtained from plasma physics and engineering constraints, while outboard radial builds are mainly determined by constraints on a neutron multiplication, a tritium-breeding ratio, and a power density. It is shown that a breeding blanket model has an impact on the radial build of a transmutation blanket. A burn cycle has to be determined to limit a fast neutron fluence of a plasma facing material below a radiation damage limit.

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Effect of Heat-Treatment on the Crystallization of B Powder and Critical Current Density Property of MgB2 Superconductor (보론 분말의 결정화에 대한 열처리 영향과 MgB2 초전도체의 임계전류밀도 특성)

  • You, Byung Youn;Kim, Chan-Joong;Park, Soon-Dong;Jun, Byung-Hyuk
    • Korean Journal of Materials Research
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    • v.24 no.9
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    • pp.465-468
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    • 2014
  • The crystallization effects of boron (B) powder on the phase, full width at half maximum (FWHM) values, and critical properties were investigated for in-situ reacted $MgB_2$ bulk superconductors. The semi-crystalline B powder was heat-treated at different temperatures of 1000, 1300 and $1500^{\circ}C$ for 5 hours in an Ar atmosphere. Then, using as-received and heat-treated B powders, the $MgB_2$ samples were prepared at $600^{\circ}C$ for 40 hours in an Ar atmosphere. As the heat-treatment temperature of the B powder increased, both the particle size of the B powder and crystalline phase increased. In the case of $MgB_2$ samples using B powders heat-treated at above $1300^{\circ}C$, unreacted magnesium (Mg) and B remained due to the improved crystallinity of the B powder. As the heat-treatment temperature of B powder increased, the critical current density of $MgB_2$ decreased continuously due to the reduction of grain boundary density and superconducting volume caused by unreacted Mg and B.

Estimation of the neutron production of KSTAR based on empirical scaling law of the fast ion stored energy and ion density under NBI power and machine size upgrade

  • Kwak, Jong-Gu;Hong, S.C.
    • Nuclear Engineering and Technology
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    • v.54 no.6
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    • pp.2334-2337
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    • 2022
  • Deuterium-tritium reaction is the most promising one in term of the highest nuclear fusion cross-section for the reactor. So it is one of urgent issues to develop materials and components that are simultaneously resistant to high heat flux and high energy neutron flux in realization of the fusion energy. 2.45 MeV neutron production was reported in D-D reaction in KSTAR and regarded as beam-target is the dominant process. The feasibility study of KSTAR to wide area neutron source facility is done in term of D-D and D-T reactions from the empirical scaling law from the mixed fast and thermal stored energy and its projection to cases of heating power upgrade and DT reaction is done.