• Nuclear Engineering and Technology
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• 제45권7호
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• pp.827-838
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• 2013

Interaction layer growth between U-Mo alloy fuel particles and Al in a dispersion fuel is a concern due to the volume expansion and other unfavorable irradiation behavior of the interaction product. To reduce interaction layer (IL) growth, a small amount of Si is added to the Al. As a result, IL growth is affected by the Si content in the Al matrix. In order to predict IL growth during fabrication and irradiation, empirical models were developed. For IL growth prediction during fabrication and any follow-on heating process before irradiation, out-of-pile heating test data were used to develop kinetic correlations. Two out-of-pile correlations, one for the pure Al matrix and the other for the Al matrix with Si addition, respectively, were developed, which are Arrhenius equations that include temperature and time. For IL growth predictions during irradiation, the out-of-pile correlations were modified to include a fission-rate term to consider fission enhanced diffusion, and multiplication factors to incorporate the Si addition effect and the effect of the Mo content. The in-pile correlation is applicable for a pure Al matrix and an Al matrix with the Si content up to 8 wt%, for fuel temperatures up to $200^{\circ}C$, and for Mo content in the range of 6 - 10wt%. In order to cover these ranges, in-pile data were included in modeling from various tests, such as the US RERTR-4, -5, -6, -7 and -9 tests and Korea's KOMO-4 test, that were designed to systematically examine the effects of the fission rate, temperature, Si content in Al matrix, and Mo content in U-Mo particles. A model converting the IL thickness to the IL volume fraction in the meat was also developed.

• 미생물학회지
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• 제53권1호
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• pp.49-54
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• 2017

Sus1 / ENY2는 진핵생물에 잘 보존된 작은 단백질로 염색사 리모델링과 mRNA 생성과정에 관여한다. Sus1 단백질은 전사 보조활성자인 SAGA 복합체와 핵공과 연관된 TREX2 복합체 등, 핵에 존재하는 2개 복합체의 구성 요소이다. 분열효모 Schizosaccharomyces pombe의 유전체 데이터에서 Sus1의 이종상동체를 찾아 기능을 분석하였다. 4분체 분석 결과 이 유전자는 생장에 필수적이 아니었으나, Sus1 유전자를 결실시키면 낮은 온도에서 생장이 느렸으며, $poly(A)^+$ RNA도 핵 안에 약간 축적되는 표현형을 보였다. 또한 Sus1-GFP 단백질은 주로 핵에 존재하였다. Yeast two-hybrid 분석과 공동면역침전 실험에서 Sus1 단백질은 TREX-2 복합체의 또 다른 구성인자인 Sac3와 상호작용을 하였다. 이와 같은 결과들은 S. pombe의 Sus1 단백질도 역시 TREX-2 복합체의 구성인자로 mRNA 방출에 관여하고 있음을 시사한다.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.820-828
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• 2018

The growing nuclear threat has amplified the need for developing diverse and accurate nuclear forensics analysis techniques to strengthen nuclear security measures. The work presented here is part of a research effort focused on developing a methodology for reactor-type discrimination of weapons-grade plutonium. To verify the developed methodology, natural $UO_2$ fuel samples were irradiated in a thermal neutron spectrum at the University of Missouri Research Reactor (MURR) and produced approximately $20{\mu}g$ of weapons-grade plutonium test material. Radiation transport simulations of common thermal reactor types that can produce weapons-grade plutonium were performed, and the results are presented here. These simulations were needed to verify whether the plutonium produced in the natural $UO_2$ fuel samples during the experimental irradiation at MURR was a suitable representative to plutonium produced in common thermal reactor types. Also presented are comparisons of fission product and plutonium concentrations obtained from computational simulations of the experimental irradiation at MURR to the nondestructive and destructive measurements of the irradiated natural $UO_2$ fuel samples. Gamma spectroscopy measurements of radioactive fission products were mostly within 10%, mass spectroscopy measurements of the total plutonium mass were within 4%, and mass spectroscopy measurements of stable fission products were mostly within 5%.

• Nuclear Engineering and Technology
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• 제16권3호
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• pp.169-179
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• 1984

FIPREL 전산코드를 사용하여 원자로 냉각수 내의 핵분열 생성물에 의한 방사능을 분석함으로써 PWR의 운전시에 발생하는 핵연료 피복관 파손을 평가할 수 있는 효과적인 절차를 모색하였다. 이 코드를 이용하여 핵연료의 농축도, 연소도, 가동온도 및 갭유출계수의 크기로 정량화되는 실제적 파손 크기등의 물리적 파라미터에 대해서 핵분열 생성물의 방사능이 나타내는 민감도에 대한 방대한 계산을 실시하였으며 그 결과는 PROFIP방법에 의한 것과 대체적으로 일치한다. 노출 우라늄이 존재하는 경우에는 옥소보다도 화학적으로 더 안정된 핵종간의 방사능비에 근거하여 반복계산을 실시함으로써 파손된 핵연료 봉에서 유출된 방사능만을 분리해 낸다. 개발된 전산코드로 파손 핵연료봉의 선형출력 밀도, 갯수, 실제적 파손 크기 및 노출우라늄의 질량등을 계산할 수 있다. 고리 1호기의 4주기에 걸친 운전 경험을 이 모텔에 의해 분석한 결과에 의하면 본 모델은 원자력발전소 정상운전시 핵연료봉의 상태를 감시·평가하는데 아주 적합한 것으로 판명되었다.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1964-1969
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• 2021

We developed a Dual-PPACs detector for fast neutron measurements that consists of two sets of PPAC: conventional PPAC and fission PPAC. A²³⁸U(U₃O₈) coating is placed in the fission PPAC's anode, which is used as the neutrons conversion layer. An experiment was performed to measure neutron time-of-flight (TOF) in which ²⁵²Cf spontaneous fission source was used. An excellent time resolution of 164ps has been observed at 6 mbar in isobutene gas. With the excellent time resolution of Dual-PPACs detector, exact neutron energy can be extracted from the timing measurement. The experimental detection efficiency was 1.9 × 10^-7, consistent with the efficiency of 2.5 × 10^-7 given by a Geant4 simulation. Ultimately, the results show that the Dual-PPACs detector is a suitable candidate for measuring fast neutrons in the future CiADS system.

• 미생물학회지
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• 제54권4호
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• pp.325-329
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• 2018

PCI 영역을 포함하고 있는 Thp1/PCID2 단백질은 mRNA 전사와 방출을 연결하는, 진화적으로 보존된 TREX-2 복합체의 구성요소이다. 분열효모인 Schizosaccharomyces pombe에서 pci2 (SPBC1105.07c) 유전자는 TREX-2 복합체의 구성요소인 Thp1 (출아효모)/PCID2 (사람)의 분열효모 이종상동체로 추정되는 PCI 영역을 갖는 단백질을 암호화하고 있다. pci2 발현을 억제하면 생장과 mRNA 방출이 모두 억제되었다. 그리고 pci2 유전자의 과발현 또한 생장을 늦추고 $poly(A)^+$ RNA를 핵 안에 약간 축적되게 하였다. 뿐만 아니라 Yeast two-hybrid와 공동침전(Co-immunoprecipitation) 분석 실험에서 Pci2는 TREX-2 복합체의 다른 구성요소인 Sac3, Dss1 단백질들과 물리적으로 상호작용하였다. 이와 같은 관찰들은 S. pombe의 Pci2 단백질도 TREX-2 복합체의 구성요소로서 mRNA 방출에 관여함을 의미한다.

• The Korean Journal of Physiology and Pharmacology
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• 제22권2호
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• pp.203-213
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• 2018

Tumor undergo uncontrolled, excessive proliferation leads to hypoxic microenvironment. To fulfill their demand for nutrient, and oxygen, tumor angiogenesis is required. Endothelial progenitor cells (EPCs) have been known to the main source of angiogenesis because of their potential to differentiation into endothelial cells. Therefore, understanding the mechanism of EPC-mediated angiogenesis in hypoxia is critical for development of cancer therapy. Recently, mitochondrial dynamics has emerged as a critical mechanism for cellular function and differentiation under hypoxic conditions. However, the role of mitochondrial dynamics in hypoxia-induced angiogenesis remains to be elucidated. In this study, we demonstrated that hypoxia-induced mitochondrial fission accelerates EPCs bioactivities. We first investigated the effect of hypoxia on EPC-mediated angiogenesis. Cell migration, invasion, and tube formation was significantly increased under hypoxic conditions; expression of EPC surface markers was unchanged. And mitochondrial fission was induced by hypoxia time-dependent manner. We found that hypoxia-induced mitochondrial fission was triggered by dynamin-related protein Drp1, specifically, phosphorylated DRP1 at Ser637, a suppression marker for mitochondrial fission, was impaired in hypoxia time-dependent manner. To confirm the role of DRP1 in EPC-mediated angiogenesis, we analyzed cell bioactivities using Mdivi-1, a selective DRP1 inhibitor, and DRP1 siRNA. DRP1 silencing or Mdivi-1 treatment dramatically reduced cell migration, invasion, and tube formation in EPCs, but the expression of EPC surface markers was unchanged. In conclusion, we uncovered a novel role of mitochondrial fission in hypoxia-induced angiogenesis. Therefore, we suggest that specific modulation of DRP1-mediated mitochondrial dynamics may be a potential therapeutic strategy in EPC-mediated tumor angiogenesis.

• Biomolecules & Therapeutics
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• 제24권4호
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• pp.363-370
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• 2016

Cardiovascular disease is the most common cause of death in diabetic patients. Hyperglycemia is the primary characteristic of diabetes and is associated with many complications. The role of hyperglycemia in the dysfunction of human cardiac progenitor cells that can regenerate damaged cardiac tissue has been investigated, but the exact mechanism underlying this association is not clear. Thus, we examined whether hyperglycemia could regulate mitochondrial dynamics and lead to cardiac progenitor cell dysfunction, and whether blocking glucose uptake could rescue this dysfunction. High glucose in cardiac progenitor cells results in reduced cell viability and decreased expression of cell cycle-related molecules, including CDK2 and cyclin E. A tube formation assay revealed that hyperglycemia led to a significant decrease in the tube-forming ability of cardiac progenitor cells. Fluorescent labeling of cardiac progenitor cell mitochondria revealed that hyperglycemia alters mitochondrial dynamics and increases expression of fission-related proteins, including Fis1 and Drp1. Moreover, we showed that specific blockage of GLUT1 improved cell viability, tube formation, and regulation of mitochondrial dynamics in cardiac progenitor cells. To our knowledge, this study is the first to demonstrate that high glucose leads to cardiac progenitor cell dysfunction through an increase in mitochondrial fission, and that a GLUT1 blocker can rescue cardiac progenitor cell dysfunction and downregulation of mitochondrial fission. Combined therapy with cardiac progenitor cells and a GLUT1 blocker may provide a novel strategy for cardiac progenitor cell therapy in cardiovascular disease patients with diabetes.

• Genomics & Informatics
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• 제16권2호
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• pp.22-29
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• 2018

Incorporation of unique barcodes into fission yeast gene deletion collections has enabled the identification of gene functions by growth fitness analysis. For fine tuning, it is important to examine barcode sequences, because mutations arise during strain construction. Out of 8,708 barcodes (4,354 strains) covering 88.5% of all 4,919 open reading frames, 7,734 barcodes (88.8%) were validated as high-fidelity to be inserted at the correct positions by Sanger sequencing. Sequence examination of the 7,734 high-fidelity barcodes revealed that 1,039 barcodes (13.4%) deviated from the original design. In total, 1,284 mutations (mutation rate of 16.6%) exist within the 1,039 mutated barcodes, which is comparable to budding yeast (18%). When the type of mutation was considered, substitutions accounted for 845 mutations (10.9%), deletions accounted for 319 mutations (4.1%), and insertions accounted for 121 mutations (1.6%). Peculiarly, the frequency of substitutions (67.6%) was unexpectedly higher than in budding yeast (~28%) and well above the predicted error of Sanger sequencing (~2%), which might have arisen during the solid-phase oligonucleotide synthesis and PCR amplification of the barcodes during strain construction. When the mutation rate was analyzed by position within 20-mer barcodes using the 1,284 mutations from the 7,734 sequenced barcodes, there was no significant difference between up-tags and down-tags at a given position. The mutation frequency at a given position was similar at most positions, ranging from 0.4% (32/7,734) to 1.1% (82/7,734), except at position 1, which was highest (3.1%), as in budding yeast. Together, well-defined barcode sequences, combined with the next-generation sequencing platform, promise to make the fission yeast gene deletion library a powerful tool for understanding gene function.

• Journal of Radiation Protection and Research
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• 제8권2호
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• pp.15-35
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• 1983

특별히 제작한 영동장치를 써서 고전압 전기영동법에 의하여 24시간 중성자 조사하고 150일 냉각한 90% 농축질산우라닐 수용액의 핵분열 생성물을 분리하였다. 핵분열생성물부터 Zr-95, Nb-95의 분리는 0.1M-$HClO_4$(pH=0.85), 0.05M-HCl+0.09M-KCl(pH=0.9), 0.1M-HCl(pH=1.1), 0.01M-HCl(pH=2.0)의 이동조건에서 가능하며 Zr-95, Nb-95는 원점부터 +1cm의 거리에서 분리된다. Zr-95와 Nb-95의 상호분리는 2% 수산암모늄을 첨가하는 경우 가능하다. 즉 0.1M-$HClO_4$, 0.05M-HCl+0.09M-KCl, 0.1M-HCl, 0.1M-식초산+0.1M- 식초산나트륨(pH=4.68)의 이동조건에서 원점부터 $-6{\sim}-7cm$ 거리에서 Nb-95, $+1{\sim}-1cm$ 거리에서 Zr-95가 각각 분리된다. 핵분열생성물부터 Ru-103의 분리는 0.025M-$Na_2CO_3+0.025M-NaHCO_3(pH=10.0)$, $0.01M-Na_3PO_4(pH=11.7)$, 0.1M-NaOH(pH=13.2)의 이동조건에서 가능하며 Ru-103는 각각 원점부터 -6cm, -4cm, -3cm거리 이동한다.