• Nuclear Engineering and Technology
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• 제48권2호
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• pp.360-367
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• 2016

A windowless spallation target can provide a neutron source and maintain neutron chain reaction for a subcritical reactor, and is a key component of China's nuclear waste transmutation of coupling accelerator and subcritical reactor. The main issue of the windowless target design is to form a stable and controllable free surface that can ensure that energy spectrum distribution is acquired for the neutron physical design when the high energy proton beam beats the lead-bismuth eutectic in the spallation target area. In this study, morphology and flow characteristics of the free surface of the windowless target were analyzed through the volume of fluid model using computational fluid dynamics simulation, and the results show that the outlet cross section size of the target is the key to form a stable and controllable free surface, as well as the outlet with an arc transition. The optimization parameter of the target design, in which the radius of outlet cross section is $60{\pm}1mm$, is verified to form a stable and controllable free surface and to reduce the formation of air bubbles. This work can function as a reference for carrying out engineering design of windowless target and for verification experiments.

• Journal of Radiation Protection and Research
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• 제7권1호
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• pp.56-60
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• 1982

핵분열(核分裂) 즉발중성자(卽發中性子)스펙트럼의 표현식(表現式)인 왓트식(式), 크란버그식(式) 및 멕스웰식(式)을 핵분열(核分裂)의 선원항(線源項)으로 취(取)하여 고디바계(系)와 제제벨계(系)의 유효증배계수(有效增倍係數)를 ANISN 전산(電算)코드로 산출(算出)하고 타(他) 연구자(硏究者)의 실험치(實驗値)와 비교(比較)해 보았다 .그 결과(結果) 실험치(實驗値)에 가장 가까운 값을 주는 것은 멕스웰식(式)으로 보였다. 이것은 곧 멕스웰식(式)이 핵분열(核分裂) 즉발중성자(卽發中性子)스펙트럼의 적절(適切)한 표현식(表現式)임을 의미(意味)한다.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1330-1338
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• 2024

Information on isotopic composition and geometric structure is necessary for identifying a true warhead. Nevertheless, such classified information should be protected physically or electronically. With a novel Hash encryption algorithm, this paper presents a Monte Carlo-based design of a neutron activation analysis verification module. The verification module employs a thermal neutron source, a non-uniform mask (physically encrypting information about isotopic composition and geometric structure), a gamma detector array, and a Hash encryption algorithm (for electronic encryption). In the physical field, a non-uniform mask is designed to distort the characteristic gamma rays emitted by the inspected item. Furthermore, as part of the Hash algorithm, a key is introduced to encrypt the data and improve the system resolution through electronic design. In order to quantify the difference between items, Hamming distance is used, which allows data encryption and analysis simultaneously. Simulated inspections of simple objects are used to quantify system performance. It is demonstrated that the method retains superior resolution even with 1% noise level. And the performances of anti-statistical attack and anti-brute force cracking are evaluated and found to be very excellent. The verification method lays a solid foundation for nuclear disarmament verification in the upcoming era.

• 한국의학물리학회지:의학물리
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• 제25권3호
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• pp.151-156
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• 2014

본 연구의 목적은 붕소 중성자 포획 치료 시 집적된 붕소 영역에서 중성자 선속의 변화와 그에 따른 방출된 즉발 감마선의 검출 시뮬레이션을 통하여 치료 영역에 대한 영상화의 가능성을 확인하고자 함이다. 전산 모사를 통하여 (1) 붕소 유무에 따른 중성자의 영향, (2) 내부와 외부에서의 즉발 감마선량 검출, (3) 즉발 감마선에 대한 에너지 스펙트럼 검출을 수행하였다. 모든 전산 모사는 Monte Carlo n-particle extended (MCNPX, Ver.2.6.0, Los Alamos National Laboratory, Los Alamos, NM, USA)를 이용하여 가상의 물 팬텀과 열중성자(thermal neutron) 소스, 붕소 영역을 지정하였다. 열중성자의 에너지는 1 eV 이하의 에너지였으며 선속은 2,000,000 n/sec.로 설정하였다. 이 때, 발생된 즉발 감마선의 검출은 물 팬텀과 수직 방향으로 위치시키고 납으로 둘러싸인 lutetium-yttrium oxyorthosilicate (Lu0,6Y1,4Si0,5:Ce; LYSO) 섬광체 검출기를 이용하였다. 붕소가 존재하는 영역인 5 cm 깊이에서의 28 분할로서 대략 0.18 cm의 bin을 도출하여 붕소 영역의 얕은 깊이에서부터 급격하게 저하되는 것을 확인하였다. 또한 붕소 영역이 시작되는 지점인 9 cm 깊이에서 감마선의 피크 레벨을 확인하였다. 그리고 478 keV 지점에서 정확한 즉발 감마선 피크가 관찰되는 것을 확인하였다. 478 keV의 즉발 감마선 피크는 41 keV의 반치폭으로 에너지 분해능 값은 8.5%로 측정되었다. 결론적으로 붕소 중성자 포획 치료 시 발생되는 즉발 감마선의 계측으로 치료가 행해지는 부위를 감마 카메라 또는 단일 광자 방출 단층 촬영 기기에서 영상화할 수 있는 가능성을 확인하였다.

• Nuclear Engineering and Technology
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• 제49권5호
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• pp.1095-1099
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• 2017

A fission source can act as a stabilization element in coupled Monte Carlo simulations. We have observed this while studying numerical instabilities in nonlinear steady-state simulations performed by a Monte Carlo criticality solver that is coupled to a xenon feedback solver via fixed-point iteration. While fixed-point iteration is known to be numerically unstable for some problems, resulting in large spatial oscillations of the neutron flux distribution, we show that it is possible to stabilize it by reducing the number of Monte Carlo criticality cycles simulated within each iteration step. While global convergence is ensured, development of any possible numerical instability is prevented by not allowing the fission source to converge fully within a single iteration step, which is achieved by setting a small number of criticality cycles per iteration step. Moreover, under these conditions, the fission source may converge even faster than in criticality calculations with no feedback, as we demonstrate in our numerical test simulations.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.7-7
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• 2011

Quantum beam technology has been expected to develop breakthroughs for nanotechnology during the third basic plan of science and technology (2006~2010). Recently, Green- or Life Innovations has taken over the national interests in the fourth basic science and technology plan (2011~2015). The NIMS (National Institute for Materials Science) has been conducting the corresponding mid-term research plans, as well as other national projects, such as nano-Green project (Global Research for Environment and Energy based on Nanomaterials science). In this lecture, the research trends in Japan and NIMS are firstly reviewed, and the typical achievements are highlighted over key nanotechnology fields. As one of the key nanotechnologies, the quantum beam research in NIMS focused on synchrotron radiation, neutron beams and ion/atom beams, having complementary attributes. The facilities used are SPring-8, nuclear reactor JRR-3, pulsed neutron source J-PARC and ion-laser-combined beams as well as excited atomic beams. Materials studied are typically fuel cell materials, superconducting/magnetic/multi-ferroic materials, quasicrystals, thermoelectric materials, precipitation-hardened steels, nanoparticle-dispersed materials. Here, we introduce a few topics of neutron scattering and ion beam nanofabrication. For neutron powder diffraction, the NIMS has developed multi-purpose pattern fitting software, post RIETAN2000. An ionic conductor, doped Pr2NiO4, which is a candidate for fuel-cell material, was analyzed by neutron powder diffraction with the software developed. The nuclear-density distribution derived revealed the two-dimensional network of the diffusion paths of oxygen ions at high temperatures. Using the high sensitivity of neutron beams for light elements, hydrogen states in a precipitation-strengthened steel were successfully evaluated. The small-angle neutron scattering (SANS) demonstrated the sensitive detection of hydrogen atoms trapped at the interfaces of nano-sized NbC. This result provides evidence for hydrogen embrittlement due to trapped hydrogen at precipitates. The ion beam technology can give novel functionality on a nano-scale and is targeting applications in plasmonics, ultra-fast optical communications, high-density recording and bio-patterning. The technologies developed are an ion-and-laser combined irradiation method for spatial control of nanoparticles, and a nano-masked ion irradiation method for patterning. Furthermore, we succeeded in implanting a wide-area nanopattern using nano-masks of anodic porous alumina. The patterning of ion implantation will be further applied for controlling protein adhesivity of biopolymers. It has thus been demonstrated that the quantum beam-based nanotechnology will lead the innovations both for nano-characterization and nano-fabrication.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1942-1946
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• 2021

Gadolinium oxysulfide (GOS) is regarded as a novel scintillator for the realization of ultra-high spatial resolution in neutron imaging. Monte Carlo simulations of GOS scintillator show that the capability of its spatial resolution is towards the micron level. Through the time-of-flight method, the light output of a GOS scintillator was measured to be 217 photons per captured neutron, ~100 times lower than that of a ZnS/LiF:Ag scintillator. A detector prototype has been developed to evaluate the imaging solution with the GOS scintillator by neutron beam tests. The measured spatial resolution is ~36 ㎛ (28 line pairs/mm) at the modulation transfer function (MTF) of 10%, mainly limited by the low experimental collimation ratio of the beamline. The weak light output of the GOS scintillator requires an enormous increase in the neutron flux to reduce the exposure time for practical applications.

• Nuclear Engineering and Technology
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• 제22권2호
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• pp.151-158
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• 1990

새로운 중성자 수송방정식의 해법인 Discrete Elements Method(DEM)를 1차원 모델에 대 한 단일 에너지 중성자 수송방정식에 적용했다. 본 연구에서는 고정선원문제와 임계계산을 행하여, 각분할법과 DEM의 계산결과의 정확도를 비교했으며 세가지의 위치차등법(DD, SC그리고 LC Scheme)중 어떤 것이 DEM에서 가장 좋은지를 오차분석을 통해 정량적으로 알아보았다. 수행한 모든 계산결과에서 같은 위치차등법을 이용할 때 DEM결과의 정확도가 각분할법으로 얻은 결과보다 훨씬 좋았으며 위치차등법중에서는 각분할 법에서와 같이 DEM에서도 LC scheme이 가장 좋은 결과를 주었다.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.448-455
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• 2020

The H.B. Robinson Unit 2 (HBR-2) pressure vessel dosimetry benchmark is an in- and ex-Reactor Pressure Vessel (RPV) neutron dosimetry benchmark based on experimental data from the HBR-2 reactor, a 2300-MW PWR designed by Westinghouse and put in operation in March 1971, openly available through the SINBAD Database at OECD/NEA data Bank. The goals of the present work were to carry out three-dimensional (3D) fixed source transport calculations in both Cartesian (X,Y,Z) and cylindrical (R,θ,Z) geometries by using the TORT-3.2 discrete ordinates code on very detailed 3D HBR-2 geometrical models and to test the latest broad-group coupled (47 neutron groups + 20 photon groups) working cross section libraries in FIDO-ANISN format with same structure as BUGLE-96, such as BUGJEFF311.BOLIB, BUGENDF70.BOLIB and BUGLE-B7. The results obtained with all the cited libraries were satisfactory and are here reported and compared.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.456.1-456.1
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• 2014

Transmutation characteristics of transuranics (TRU) in a transmutation reactor based on LAR (Low Aspect Ratio) tokamak as a neutron source are investigated. Optimum radial build of a transmutation reactor is found by coupled analysis of the tokamak systems and the neutron transport. The dependence of the transmutation characteristics on an aspect ratio, A in the range of 1.5 to 2.5, and on a fusion power in the range of 150 MW to 500 MW are investigated. Equilibrium fuel cycle is developed for effective transmutation and it is shown that with one unit of the transmutation reactor based on the LAR tokamak producing fusion power in the range of a few hundred MW, up to 3 PWRs (1.0 GWe capacity) can be supported with the burn-up fraction bigger than 50%.