• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4583-4590
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• 2023

This study aims at modeling the beryllium reflector poisoning under neutron irradiation conditions and calculating the impact of beryllium poisoning on the core parameters of ETRR-2 research reactor. The CITVAP code was used to calculate the neutron flux and parameters of ETRR-2 core with beryllium reflector elements. The neutron flux in each reflector element was calculated to solve the modeling equations for the atomic densities of lithium-6 (⁶Li), tritium-3 (³H), and helium-3 (³He) using the BERYL program. The results are discussed based on CITVAP calculations of the core excess reactivity and cycle length Full Power Days (FPD). Possible solutions to minimize the degradation due to beryllium poisoning are also discussed and compared based on calculations.

• 소성∙가공
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• 제9권3호
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• pp.293-303
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• 2000

Recent developments of Fe technology make it possible to apply CAD/CAE/CAM techniques successfully to the stamping die design among the automotive parts industries. Those successful applications are greatly attributable to the development of commercial S/W. Up to now most commercial S/W for the analysis of sheet metal forming is based on the dynamic explicit algorithm. The main characteristics of dynamic explicit algorithm is that there is no convergence problem if the time increment is taken less than the stability limit. The stability of the analysis is guaranteed in the commercial code, since the adequate time increment is computed from the so called "Courant Condition". However excess computing time is often pointed out in the dynamic explicit analysis according to the characteristics of process parameters taken. In the study, various parameters that may affect the stability and the method how to improve computational efficiency of analysis have been investigated.estigated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.492-499
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• 1997

Experimental research was conducted to investigate structural performance of concrete columns confined with welded reinforcement grids were tested under simulated seismic loading. The columns were subjected to constant axial compression accompanied by incrementally increasing lateral deformation reversals. The results indicate thar welded reinforcement grid can be used effectively as confinement reinforcement provided that the steel used, have sufficient ductility and the welding process employed does not alter the strength and elongation characteristics of steel. The grids improved the structural performance of columns, which developed lateral drift ratios in excess of 3% with the spacing and volumetric ratio of transverse reinforcement similar to those required by the ACI 318-95 Building Code.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1729-1737
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• 2019

This paper presents neutronics design of VVER-1000 fuel assembly using burnable poison particles (BPPs) for controlling excess reactivity and pin-wise power distribution. The advantage of using BPPs is that the thermal conductivity of BPP-dispersed fuel pin could be improved. Numerical calculations have been conducted for optimizing the BPP parameters using the MVP code and the JENDL-3.3 data library. The results show that by using $Gd_2O_3$ particles with the diameter of $60{\mu}m$ and the packing fraction of 5%, the burnup reactivity curve and pin-wise power distribution are obtained approximately that of the reference design. To minimize power peaking factor (PPF), total BP amount has been distributed in a larger number of fuel rods. Optimization has been conducted for the number of BPP-dispersed rods, their distribution, BPP diameter and packing fraction. Two models of assembly consisting of 18 BPP-dispersed rods have been selected. The diameter of $300{\mu}m$ and the packing fraction of 3.33% were determined so that the burnup reactivity curve is approximate that of the reference one, while the PPF can be decreased from 1.167 to 1.105 and 1.113, respectively. Application of BPPs for compensating the reduction of soluble boron content to 50% and 0% is also investigated.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.869-877
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• 2020

A 24-month Advanced Power Reactor 1400 (APR1400) core with a very-low-boron (VLB) concentration has been investigated for an inherently safe and high-performance PWR in this work. To develop a high-performance APR1400 which is able to do the passive frequency control operation, VLB feature is essential. In this paper, the centrally-shielded burnable absorber (CSBA) is utilized for an efficient VLB operation in the 24-month cycle APR1400 core. This innovative design of the VLB APR1400 core includes the optimization of burnable absorber and loading pattern as well as axial cutback for a 24-month cycle operation. In addition to CSBA, an Er-doped guide thimble is also introduced for partial management of the excess reactivity and local peaking factor. To improve the neutron economy of the core, two alternative radial reflectors are adopted in this study, which are SS-304 and ZrO₂. The core reactivity and power distributions for a 2-batch equilibrium cycle are analyzed and compared for each reflector design. Numerical results show that a VLB core can be successfully designed with 24-month cycle and the cycle length is improved significantly with the alternative reflectors. The neutronic analyses are performed using the Monte Carlo Serpent code and 3-D diffusion code COREDAX-2 with the ENDF/B-VII.1.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.499-507
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• 2020

Research reactors for radioisotope production, fuel and material testing and research activities are designed, constructed and operated based on the society's needs. In this study, neutronic and thermal hydraulic design of a high neutron flux research reactor core for radioisotope production is presented. Main parameters including core excess reactivity, reactivity variations, power and flux distribution during the cycle, axial and radial power peaking factors (PPF), Pu₂₃₉ production and minimum DNBR are calculated by nuclear deterministic codes. Core calculations performed by deterministic codes are validated with Monte Carlo code. Comparison of the neutronic parameters obtained from deterministic and Monte Carlo codes indicates good agreement. Finally, subchannel analysis performed for the hot channel to evaluate the maximum fuel and clad temperatures. The results show that the average thermal neutron flux at the beginning of cycle (BOC) is 1.0811 × 10¹⁴ n/㎠-s and at the end of cycle (EOC) is 1.229 × 10¹⁴ n/㎠-s. Total Plutonium (Pu₂₃₉) production at the EOC evaluated to be 0.9487 Kg with 83.64% grade when LEU (UO₂ with 3.7% enrichment) used as fuel. This designed reactor which uses LEU fuel and has high neutron flux and low plutonium production could be used for peaceful nuclear activities based on nuclear non-proliferation treaty concepts.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.47-58
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• 2015

Four recycling scenarios involving pyroprocessing of spent fuel (SF) have been investigated for a 600-MWe transmutation sodium-cooled fast reactor (SFR), KALIMER. Performance evaluation was done with code system REBUS connected with TRANSX and TWODANT. Scenario Number 1 is the pyroprocessing of Canada deuterium uranium (CANDU) SF. Because the recycling of CANDU SF does not have any safety problems, the CANDU-Pyro-SFR system will be possible if the pyroprocessing capacity is large enough. Scenario Number 2 is a feasibility test of feed SF from a pressurized water reactor PWR. Thefsensitivity of cooling time before prior to pyro-processing was studied. As the cooling time sensitivity of cooling time before prior to pyro-processing was studied. As the cooling time increases, excess reactivity at the beginning of the equilibrium cycle (BOEC) decreases, thereby creating advantageous reactivity control and improving the transmutation performance of minor actinides. Scenario Number 3 is a case study for various levels of recovery factors of transuranic isotopes (TRUs). If long-lived fission products can be separated during pyroprocessing, the waste that is not recovered is classified as low- and intermediate-level waste, and it is sufficient to be disposed of in an underground site due to very low-heat-generation rate when the waste cooling time becomes >300 years at a TRU recovery factor of 99.9%. Scenario Number 4 is a case study for the recovery factor of rare earth (RE) isotopes. The RE isotope recovery factor should be lowered to ${\leq}20%$ in order to make sodium void reactivity less than <7$, which is the design limit of a metal fuel.

• 농약과학회지
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• 제16권2호
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• pp.109-120
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• 2012

본 연구는 2011년 서울 북부지역에서 유통되고 있는 농산물 2,914건을 대상으로 GC, HPLC, GC-MSD 및 LC-MSD을 이용한 다종농약다성분분석법에 따라 284종 대한 잔류농약 실태를 조사하였다. 농산물 중 431건에서 농약이 검출되어 14.8%의 검출률을 나타냈으며, 농약 검출빈도가 높은 농산물은 들깻잎 40.0%(28/70), 참나물 35.5%(11/31), 비름나물 30.0%(3/10), 시금치 27.7%(38/137) 순이었다. 이 중 농약잔류허용기준을 초과한 농산물은 31건으로 부적합률은 1.0% 였으며 인삼 6건(19.4%), 들깻잎, 부추 각각 4건(12.9%), 파, 돌나물 각각 3건(9.7%), 시금치, 상추 각각 1건(3.2%)등이었다. 분석대상 농약 284종 중에서 검출된 농약 성분은 59종으로 이 중 잔류허용기준을 초과한 농약은 21종이었다. 농약의 용도별 분포를 보면 살균제(56.4%)가 살충제(42.1%)에 비해 검출빈도가 높았다. Procymidone의 검출빈도가 가장 높았고 이 중 잔류허용기준을 초과한 농약은 tolclofos-methyl, endosulfan, dimethomorph, diniconazole, fludioxonil이였다. 판매점별 분포를 살펴보면 유통되는 농산물의 잔류농약 검출률은 직거래 장터가, 잔류농약기준 초과률은 전통시장이 가장 높았다. 배추에서 검출된 각 농약의 안전성 평가를 위한 PADI 대비 식이섭취율은 diazinon에서 2.9901 %로 가장 높게 나타났고 다른 모든 농약도 3.0% 미만으로 나타나 모두 PADI 대비 위해도가 낮은 것으로 확인되어 안전한 것으로 나타났다.

• 콘크리트학회지
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• 제11권2호
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• pp.187-196
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• 1999

지진다발 지역에서는 철근콘크리트 기둥의 단면을 합리적으로 구속함과 동시에 횡보강 띠철근의 세심한 배근등이 요구된다. 이러한 요구조건을 만족시키기 위한 보편적인 횡보강근 사용의 문제점으로는 높은 체적비(high volumetric ratio), 조밀한 간격(close spacings), 겹침(overlapping of hoops), 구부림(bends), 구부림 연장 (bend extensions), 시공상의 어려움과 콘크리트 타설상의 문제 등이다. 이러한 문제점을 해결하기 위한 한 방법으로는 요구되는 횡보강근의 체적비, 배역, 크기 등에 따라 이를 기조립, 용접하여 사용하는 것이다. 용접된 횡보강근의 사용은 겹침과 구부림, 구부림의 연장 등이 필요하지 않기 때문에 조립이 간편하고, 축방향 철근의 지지에 적합한 치수의 정확성과 재료를 절감시킬 수 있다. 더우기, 단면 내 횡보강 철근의 간격이 조밀해짐으로써, 코아 콘크리트 주변의 구속력을 균등히 분배시키게 되고, 이에 따라 코아 콘크리트의 거동을 향상시키는 결과를 얻을 수가 있다. 이에 본 연구에서는 이러한 용접 띠철근으로 보강된 철근콘크리트 기둥의 역학적 거동을 실험적으로 규명함과 동시에 철근콘크리트 기둥의 내진성능 향상을 위한 기초자료를 제공하고자 하였다. 그 결과 횡보강근의 강도와 연성에 영향을 미치지 않도록 용접됨과 동시에 충분한 신률을 가진다면, 용접된 격자형 횡보강근은 기둥의 띠철근으로써 사용가능한 것으로 판단된다. 특히, 용접된 격자형 횡보강근이 유효하게 거동하기 위하여는 1) 용접된 접합부위의 강도가 보강근의 모재강도 이상 2) 신률이 4% 이상이어야 할 필요가 있다.

• 한국식품영양과학회지
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• 제38권12호
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• pp.1779-1784
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• 2009

우리 국민의 주식이 되는 쌀(백미)과 콩류, 감귤류, 열대과 일류, 엽채류, 엽경채류, 근채류, 과채류, 버섯류에 속하는 농산물(989건)에 대해 8종의 EBI계 농약의 잔류 여부를 분석하였다. 그 결과 8건의 검체에서 농약이 검출되었고 농약 수는 5종이 검출되었다. 기준 미설정 농약은 2종이었으며, 곡류 134건 중 4건 검출로 3.0%, 채소류 471건 중 4건 검출로 0.8%의 검출율을 나타내었다. 그 외 콩류(48건), 견과종실류(72건), 과실류(197건), 버섯류(67건)에서는 전혀 검출되지 않았으며 부적합율은 0.1%로 나타났다. 국내 미등록농약인 paclobutrazole이 근대에서 잠정허용기준을 초과하는 것으로 확인되었다. 그리고 EBI계의 검출율은 0.8%로 매우 낮았으며 검출된 농약의 경우도 기준규격 이하로 안전한 수준이었다.