• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3080-3087
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• 2023

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 Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ 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 Bi₂Te_2.7Se_0.3 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 Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.39-48
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• 2024

Research reactors are operated under ambient temperature and atmospheric pressure, which is much less severe conditions compared to those in typical nuclear power plants. Due to the high temperature, heat resistant materials such as austenite stainless steel should be used for the reactors in typical nuclear power plants. Whereas, as the effect of temperature is low for research reactors, materials with high resistance to neutron irradiation, such as zircaloy and beryllium, are used. Therefore, these conditions should be considered when performing integrity assessment for research reactors. In this study, a computational technique through finite element (FE) analysis was developed considering the operating conditions and materials of research reactor when conducting integrity assessment. Neutron irradiation analysis techniques using thermal expansion analysis were proposed to consider neutron irradiation growth and swelling in zirconium alloys and beryllium. A user subroutine program that can calculate the strain rate induced by neutron irradiation creep was developed for use in the commercial analysis program Abaqus. To validate the proposed technique and the user subroutine, FE analysis results were compared with hand-calculation results, and showed good agreement. Consequently, developed technique and user subroutine are suitable for evaluating structural integrity of research reactors.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.402-409
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• 2024

High energy neutron irradiations impact on structural and electrical properties of alumina are studied with particular emphasis on real time in-situ radiation induced conductivity measurement in low flux region. Polycrystalline Al₂O₃ samples are subjected to high energy neutrons produced from D-T neutron generator and Am-Be neutron source. 14 MeV neutrons from D-T generator are chosen to study the role of fast neutron irradiation in the structural modification of samples. Real time in-situ electrical measurement is performed to investigate the change in insulation resistance of Al₂O₃ due to radiation induced conductivity at low flux regime. During neutron irradiation, a significant transient decrease in insulation resistance is observed which recovers relative higher value just after neutron exposure is switched off. XRD results of 14 MeV neutron irradiated samples suggest annealing effect. Impact of relatively low energy neutrons on the structural properties is also studied using Am-Be neutrons. In this case, clustering is observed on the sample surface after prolonged neutron exposure. The structural characterizations of pristine and irradiated Al₂O₃ samples are performed using XRD, SEM, and EDX. The results from these characterizations are analysed and interpreted in the manuscript.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1472-1482
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• 2017

Zirconium alloy cladding tube specimens were irradiated at $380^{\circ}C$ up to a fast neutron fluence of $7.5{\times}10^{24}n/m^2$ in a research reactor to investigate the effect of neutron irradiation on hydride reorientation and mechanical property degradation. Cool-down tests from $400^{\circ}C$ to $200^{\circ}C$ under 150 MPa tensile hoop stress were performed. These tests indicate that the irradiated specimens generated a smaller radial hydride fraction than did the unirradiated specimens and that higher hydrogen content generated a smaller radial hydride fraction. The irradiated specimens of 500 ppm-H showed smaller ultimate tensile strength and plastic strain than those characteristics of the 250 ppm-H specimens. This mechanical property degradation caused by neutron irradiation can be explained by tensile hoop stress-induced microcrack formation on the hydrides in the irradiation-damaged matrix and subsequent microcrack propagation along the hydrides and/or through the matrix.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.438-441
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• 2021

The electrical characteristics of single-crystal composite superconductors produced by a melting process were studied by neutron irradiation. In order to improve the current characteristics of the YBa₂Cu₃O_7-y superconductor, it is necessary to form an effective flux pinning center inside the superconductor. In this study, an increase in flux pinning was attempted through neutron irradiation onto YBa₂Cu₃O_7-y superconductors. The neutron irradiation was performed at 30 MeV for 500 sec, The electrical properties of the superconductors were measured in a magnetic field of 5 Tesla at 50 K using a magnetic properties measurement system (MPMS). After neutron irradiation, the critical current density of the YBa₂Cu₃O_7-y superconductor in a 1 Tesla magnetic field was 1×10⁵ A/cm². Once neutrons were irradiated at 30 MeV and 10 μA for 500 sec, the critical current density was observed to increase significantly. When neutrons are irradiated to a superconductor, micro-defects are created in the superconductor, and they act as flux pinning centers that hold the magnetic field generated when an electric current flows.

• 한국산학기술학회논문지
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• 제3권3호
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• pp.165-169
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• 2002

반도체 소자의 기판 재료로 사용되고 있는 실리콘 웨이퍼는 그 정밀도가 매우 중요하다. 본 연구에서는 균일한 Dopant농도 분포를 얻을 수 있는 중성자 변환 Doping을 이용하여 실리콘에 인(P)을 Doping하는 연구를 수행하였다. 본 연구에서는 하나로 원자로를 이용하여 고저항(1000∼2000Ωcm) FZ실리콘 웨이퍼에 중성자 조사하여 저항의 변화를 관찰하였고, 중성자 조사시 발생하는 점결함을 분석하여 점결함이 저항 변화에 미치는 영향을 알아보았다. 중성자 조사 전 이론적 계산에 의해 HTS조사공은 5Ωcm, 20.1Ωcm이고 IP3조사공은 5Ωcm, 26.5Ωcm, 32.5Ωcm이었고, 중성자 조사 후 SRP로 측정한 결과 실제 저항값은 HTS-1 2.10Ωcm, HTS-2 7.21Ωcm이었고. IP-1은 1.79Ωcm, IP-2는 6.83Ωcm, 마지막으로 IP-3는 9.23Ωcm이었다. DLTS측정 결과 IP조사공에서 새로운 피크의 결함을 발견할 수 있었다. 또한 중성자 조사후의 저항변화는 열중성자량에 의존하며 조사공의 종류와는 무관하다.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.109.1-109.1
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• 2003

The aim of this study was to investigate the biological effects of blood and testis by neutron or gamma-ray irradiation in black mouse. Six-week-old C57BL male mice were irradiated with neutron (flux: 1.036739E+09) or Co60 gamma rays(dose rate: lGy/min.) The irradiation method of animal was abdominal irradiation and dose of irradiation was 10 and 20 Gy added with 5 and 15Gy in neutron irradiation.. After that, the mice were sacrificed 3 days later. Blood and testis were taken and then composition of blood in blood cell were investigated. (omitted)

• Journal of Ginseng Research
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• 제14권3호
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• pp.357-363
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• 1990

When mice irradiated by neutron (Be) are fed with ginseng concentrate, ginseng powder, and adaptagen of which the major ingredient is ginseng alkaloid to neutron (Be source) irradiated mouse, the following results are obtained. 1. The 50% lethal dose (LD50) for the neutron irradiation were 4 days at 600 rad, 7 days at 500 rad, 16 days at 400 rad, 33 days at 375 rad, and 55 days at 350 rad. In thistest, the standard amollntofirradiation was set at 375 rad/8 min. 2. Some spots appeared in the tail of the neutron-irradiated mouse because of blood congestion, and some had its tip tails cut. But the group administered with adaptagen did not show any of these symptoms. 3. The neutron irradiated mouse showed darkening the color of their lung-chloasmas while none of the adaptagen group had this symptom. 4. The lung tissue of the neutron irradiated mouse showed an increase of the karyolysis and cytoplasmic vacuole. 5. When both neutron irradiation and the ginseng sllbstances were given to the mouse at the same day, the 50% lethal days were increased to 29-33 days for the group administered with ginseng extract. 67 days for the group given with the ginseng powder. and 80 days for the groilp arith the adaptagen. 6. The survival rate of those fed with adaptagen for 33 days before the neutron-irradiation was 100%, while the 50% lethal daysofthe group fed with ginsengextract were 39 days and that of the group fed with ginseng powder were 69 days. 7. The serum valued of ${\gamma}$-globulin, IgG, and albumin were returned to normal condition in the group fed with adaptagen for 33 days before the neutron-irradiation. But those of the group which were given the irradiation and the ginseng substances at the same day did not show such a recovery.

• The Journal of the Acoustical Society of Korea
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• 제18권1E호
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• pp.7-12
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• 1999

In relation to a non-destructive evaluation of irradiation damages, the changes in the hysteresis loop and Barkhausen noise amplitude and the harmonics frequency due to a neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of RPV was irradiated to a neutron fluence of 2.3 ×10/sup 19/ n/㎠ (E ≥1 MeV) at 288℃. The saturation magnetization of neutron irradiated metal did not change. The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by a neutron irradiation. The spectrum of Barkhausen noise is analysed with an applied frequency of 4 Hz and 8 Hz, sampling time of 50 μ sec and 20 μ sec. The harmonic frequency shows 4 Hz, 8 Hz, 12 Hz and 16 Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared on the irradiated specimen. In addition to the amplitude, the harmonic frequency of Barkhausen noise is taken into accounts as a promising tool for monitoring the irradiation induced degradation of the reactor materials such as a SA508 of PWR-RPV steel and a Zr₄ of HANARO-CNH.

• Journal of Radiation Protection and Research
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• 제31권1호
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• pp.31-35
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• 2006

Black mouse에 하나로 원자로의 BNCT시설을 이용하여 중성자(flux:1.036739E+09)를 머리를 정면으로 16 및 32 Gy 조사한 후 생물학적 효과를 관찰하는 일환으로 고환에 대한 물리학적 변화 및 조직 변화를 관찰하였다. 조사 후 90일이 경과한 후에 고환의 무게는 변화가 없었으나 고환의 부피는 약간 감소하였으며, 정자수도 감소하였다. 고환의 조직검사에서는 32 Gy 중성자 조사군에서 위축된 정세관의 수가 증가되었으며 stage VI에서의 정세관에서는 정조세포 및 비사기 정모세포가 고갈되어 있음을 알 수 있었다. 중성자 조사(32 Gy)후 고환의 손상이 장기간 경과 후에도 회복되지 않음을 알 수 있었다.