• 한국지진공학회논문집
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• 제25권2호
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• pp.53-58
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• 2021

Nuclear power plant's safety against seismic events is evaluated as risk values by probabilistic seismic safety assessment. The risk values vary by the seismic failure correlation between the structures, systems, and components (SSCs). However, most probabilistic seismic safety assessments idealized the seismic failure correlation between the SSCs as entirely dependent or independent. Such a consideration results in an inaccurate assessment result not reflecting real physical phenomenon. A nuclear power plant's seismic risk should be calculated with the appropriate seismic failure correlation coefficient between the SSCs for a reasonable outcome. An accident scenario that has an enormous impact on a nuclear power plant's seismic risk was selected. Moreover, the probabilistic seismic response analyses of a nuclear power plant were performed to derive appropriate seismic failure correlations between SSCs. Based on the analysis results, the seismic failure correlation coefficient between SSCs was derived, and the seismic fragility curve and core damage frequency of the loss of essential power event were calculated. Results were compared with the seismic fragility and core damage frequency of assuming the seismic failure correlations between SSCs were independent and entirely dependent.

• 한국수정란이식학회지
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• 제33권4호
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• pp.327-336
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• 2018

To date, there are no protocols optimized to the effective separation of spermatogonial stem cells (SSCs) from testicular cells derived from mouse testes, thus hindering studies based on mouse SSCs. In this study, we aimed to determine the most efficient purification method for the isolation of SSCs from mouse testes among previously described techniques. Isolation of SSCs from testicular cells derived from mouse testes was conducted using four different techniques: differential plating (DP), magnetic-activated cell sorting (MACS) post-DP, MACS, and positive and negative selection double MACS. DP was performed for 1, 2, 4, 8, or 16 h, and MACS was performed using EpCAM ($MACS^{EpCAM}$), Thy1 ($MACS^{Thy1}$), or GFR ${\alpha}1$ ($MACS^{GFR{\alpha}1}$) antibodies. The purification efficiency of each method was analyzed by measuring the percentage of cells that stained positively for alkaline phosphatase. DP for 8 h, $MACS^{Thy1}$ post-DP for 8 h, $MACS^{GFR{\alpha}1}$, positive selection double $MACS^{GFR{\alpha}1/EpCAM}$, and negative selection double $MACS^{GFR{\alpha}1/{\alpha}-SMA}$ were identified as the optimal protocols for isolation of SSCs from mouse testicular cells. Comparison of the purification efficiencies of the optimized isolation protocols showed that, numerically, the highest purification efficiency was obtained using $MACS^{GFR{\alpha}1}$. Overall, our results indicate that $MACS^{GFR{\alpha}1}$ is an appropriate purification technique for the isolation of SSCs from mouse testicular cells.

• International Journal of Stem Cells
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• 제16권1호
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• pp.27-35
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• 2023

Background and Objectives: Spermatogonial stem cells (SSCs) are the most primitive cells in spermatogenesis and are the only adult stem cells capable of passing on the genome of a given species to the next generation. SSCs are the only adult stem cells known to exhibit high Oct4 expression and can be induced to self-reprogram into pluripotent cells depending on culture conditions. Epigenetic modulation is well known to be involved in the induction of pluripotency of somatic cells. However, epigenetic modulation in self-reprogramming of SSCs into pluripotent cells has not been studied. Methods and Results: In this study, we examined the involvement of epigenetic modulation by assessing whether selfreprogramming of SSCs is enhanced by treatment with epigenetic modulators. We found that second-generation selective class I HDAC inhibitors increased SSC reprogramming efficiency, whereas non-selective HDAC inhibitors had no effect. Conclusions: We showed that pluripotent stem cells derived from adult SSCs by treatment with small molecules with epigenetic modulator functions exhibit pluripotency in vitro and in vivo. Our results suggest that the mechanism of SSC reprogramming by epigenetic modulator can be used for important applications in epigenetic reprogramming research.

• 대한소아치과학회지
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• 제48권3호
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• pp.344-351
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• 2021

이 연구의 목적은 타이타늄-질소 코팅된 금속관(TiNCs)의 표면 경도와 스테인리스 스틸 금속관(SSCs)의 표면 경도를 비교하고, TiNCs의 부식 저항성 및 물리적 자극에 대한 금색 코팅의 안정성을 평가하는 것이다. 표면 경도 시험을 위해 10개의 TiNCs와 10개의 SSCs를 사용하였다. 각 금속관 종류당 총 30번의 경도를 측정하여 평균값을 구하고 비교하였다. 부식 저항성 시험을 위해 직사각형 형태의 TiNC와 SSC의 원재료(금속관으로 가공되기 전 판상 형태)를 준비하였다. 각 금속관 종류 당 2회의 부식 시험을 시행하였다. 부식 용액에 용출된 금속 이온의 총 양을 유도결합 플라즈마 분광분석기로 측정하였다. 5개의 TiNCs로 반복적으로 가해지는 칫솔력에 대한 색조 안정성 시험을 시행하였다. TiNCs의 평균 경도는 SSCs의 평균 경도보다 유의미하게 높았다. TiNCs와 SSCs의 원재료로부터 용출된 금속 이온의 총 합은 ISO 22674(재료의 무결성에 관한 기준) 기준치를 넘지 않음을 확인했다. TiNCs의 금색 코팅은 반복적인 물리적 자극에 대하여 주어진 시간 동안 안정성을 가졌다.

• 한국압력기기공학회 논문집
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• 제14권1호
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• pp.48-57
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• 2018

Configuration management (CM) is the process of identifying and documenting characteristics of plant structures, systems and components (SSCs), and of ensuring that changes to these characteristics are properly assessed, approved, implemented, verified and recorded. The purpose of this study is to examine regulation and technical standards developed under different concepts and level of depth for classification of nuclear SSCs as an essential prerequisite of the CM. In this context, main contents of currently adopted NSSC Notice 2016-10 are reviewed and compared with those in recently published ANSI/ANS 58.14 and IAEA SSG-30. The technical standards were prototypically used for classification of O-rings in two nuclear systems. It is found that ANSI/ANS 58.14 results in different categories taking into account specific features while IAEA SSG-30 leads to same categorization of the O-rings. Key findings will be summarized for Korean regulatory amendment in the future.

• 한국지하수토양환경학회지:지하수토양환경
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• 제23권4호
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• pp.1-15
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• 2018

Despite of safety issues related to radiological hazards, 31 countries around the world are operating more than 450 nuclear power plants (NPPs). To operate NPPs safely, safety regulations from radiation protection organizations were developed and adopted in many countries. However, many cases of radionuclide releases at foreign NPPs have been reported. Almost all commercial NPPs routinely release radioactive materials to the surrounding environments as liquid and gas phases under control. These releases are called 'planned releases' which are planned, regularly monitored, and well documented. Meanwhile, the releases focused in this review, called 'unplanned releases', are neither planned nor monitored by regulatory and/or protection organizations. NPPs are generally composed of various structures, systems and components (SSCs) for safety. Among them, the SSCs near reactors are closely related to safety of NPPs, and typically fabricated to comply with stringent requirements. However, some non-safety related SSCs such as underground pipes may be constructed only according to commercial standards, causing the leakage of radioactive fluids usually containing tritium ($^3H$). This paper discusses SSCs of NPPs and introduces several cases of unplanned releases at foreign NPPs. The current regulation on the environmental radiological surveillance and assessment around the NPPs in South Korea are also examined.

• Journal of Astronomy and Space Sciences
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• 제32권3호
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• pp.181-187
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• 2015

Storm sudden commencements (SSCs) occur due to a rapid compression of the Earth's magnetic field. This is generally believed to be caused by interplanetary (IP) shocks, but with exceptions. In this paper we explore possible causes of SSCs other than IP shocks through a statistical study of geomagnetic storms using SYM-H data provided by the World Data Center for Geomagnetism - Kyoto and by applying a superposed epoch analysis to simultaneous solar wind parameters obtained with the Advanced Composition Explorer (ACE) satellite. We select a total of 274 geomagnetic storms with minimum SYM-H of less than -30nT during 1998-2008 and regard them as SSCs if SYM-H increases by more than 10 nT over 10 minutes. Under this criterion, we found 103 geomagnetic storms with both SSC and IP shocks and 28 storms with SSC not associated with IP shocks. Storms in the former group share the property that the strength of the interplanetary magnetic field (IMF), proton density and proton velocity increase together with SYM-H, implying the action of IP shocks. During the storms in the latter group, only the proton density rises with SYM-H. We find that the density increase is associated with either high speed streams (HSSs) or interplanetary coronal mass ejections (ICMEs), and suggest that HSSs and ICMEs may be alternative contributors to SSCs.

• 한국전산구조공학회논문집
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• 제34권5호
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• pp.319-325
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• 2021

후쿠시마 원전사고 발생으로 다수기의 지진안전성에 관한 연구의 필요성이 부각되었다. 한 부지에 건설된 원자력발전소의 경우 유사한 지진응답을 보이기 때문에 적게나마 원자력발전소 SSCs간의 지진손상에 대하여 상관성이 존재하므로 합리적 지진안전성 평가를 위하여 지진손상 상관성을 고려하여야 한다. 본 연구에서는 쌍둥이 호기의 필수전원상실사건에 대하여 확률론적 지진안전성 평가를 수행하였다. 적절한 지진손상 상관계수를 도출하기 위하여 확률론적 지진응답해석을 수행하여 적용하였다. External Event Mensuration System 프로그램을 활용하여 다수기의 필수전원상실사건의 고장수목을 구성하여 지진취약도 및 지진리스크를 분석하였다. 또한 SSCs간의 지진손상 상관성을 완전독립 및 완전종속으로 고려하여 비교 분석을 수행하였다.

• 한국지진공학회논문집
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• 제23권2호
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• pp.101-108
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• 2019

The seismic safety of nuclear power plants has always been emphasized by the effects of accidents. In general, the seismic safety evaluation of nuclear power plants carries out a seismic probabilistic safety assessment. The current probabilistic safety assessment assumes that damage to the structure, system, and components (SSCs) occurs independently to each other or perfect dependently to each other. In case of earthquake events, the failure event occurs with the correlation due to the correlation between the seismic response of the SSCs and the seismic performance of the SSCs. In this study, the EEMS (External Event Mensuration System) code is developed which can perform the seismic probabilistic safety assessment considering correlation. The developed code is verified by comparing with the multiplier n, which is for calculating the joint probability of failure, which is proposed by Mankamo. It is analyzed the changes in seismic fragility curves and seismic risks with correlation. As a result, it was confirmed that the seismic fragility curves and seismic risk change according to the failure correlation coefficient. This means that it is important to select an appropriate failure correlation coefficient in order to perform a seismic probabilistic safety assessment. And also, it was confirmed that carrying out the seismic probabilistic safety assessment in consideration of the seismic correlation provides more realistic results, rather than providing conservative or non-conservative results comparing with that damage to the SSCs occurs independently.

• Anatomy and Cell Biology
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• 제56권4호
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• pp.508-517
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• 2023

In cancer patients, chemo/radio therapy may cause infertility by damaging the spermatogenesis affecting the self-renewal and differentiation of spermatogonial stem cells (SSCs). In vitro differentiation of stem cells especially mesenchymal stem cells (MSCs) into germ cells has recently been proposed as a new strategy for infertility treatment. The aim of this study was to evaluate the proliferation and differentiation of SSCs using their co-culture with Sertoli cells and conditioned medium (CM) from adipose tissue-derived MSCs (AD-MSCs). Testicular tissues were separated from 2-7 days old neonate Wistar Rats and after mechanical and enzymatic digestion, the SSCs and Sertoli cells were isolated and cultured in Dulbecco's modified eagle medium with 10% fetal bovine serum, 1X antibiotic, basic fibroblast growth factor, and glial cell line-derived neurotrophic factor. The cells were treated with the CM from AD-MSCs for 12 days and then the expression level of differentiation-related genes were measured. Also, the expression level of two major spermatogenic markers of DAZL and DDX4 was calculated. Scp3, Dazl, and Prm1 were significantly increased after treatment compared to the control group, whereas no significant difference was observed in Stra8 expression. The immunocytochemistry images showed that DAZL and DDX4 were positive in experimental group comparing with control. Also, western blotting revealed that both DAZL and DDX4 had higher expression in the treated group than the control group, however, no significant difference was observed. In this study, we concluded that the CM obtained from AD-MSCs can be considered as a suitable biological material to induce the differentiation in SSCs.