http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Efficacy analysis of hydrogen mitigation measures of CANDU containment under LOCA scenario
Choi, Wonjun,Yu, Seon Oh,Kim, Sung Joong Elsevier 2018 Annals of nuclear energy Vol.118 No.-
<P><B>Abstract</B></P> <P>Mitigation of hydrogen risk has been a critical objective to assure ultimate safety of the nuclear power plant (NPP). Since the CANDU containment showed potential vulnerability over hydrogen explosion during severe accident, efficacy of hydrogen mitigation measures equipped in the current CANDU NPP need to be investigated thoroughly. Herein we report the effect of mitigation measures such as spray, igniter, passive autocatalytic recombiner (PAR), local air cooler (LAC), and filtered containment venting system (FCVS) on the hydrogen behavior using MELCOR 2.1 code. Wolsong Unit 1 was selected for target NPP and Loss of Coolant Accident (LOCA) was assumed as a plausible severe accident scenario. The analysis showed that the hydrogen concentration in the lower region of the containment was higher in the unmitigated base case. The application of FCVS with other safety measures successfully prevented the containment failure. Expected safety function of the FCVS was to filter out the fission products but substantial amount of oxygen was also vented out. This leads to the oxygen starvation in the containment and prevention of the containment failure in the long run.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen risk of Wolsong Unit 1 under LOCA scenario was analyzed using the MELCOR code. </LI> <LI> Efficacy of accident mitigation features including FCVS was analyzed. </LI> <LI> Oxygen starvation with high hydrogen concentration was predicted as the result of venting and combustion. </LI> </UL> </P>
Choi, Wonjun,Kim, Hwan-Yeol,Park, Rae-Joon,Kim, Sung Joong Atomic Energy Society of Japan 2017 Journal of nuclear science and technology Vol.54 No.3
<P>During a steam generator tube rupture (SGTR) accident, direct release of radioactive nuclides into the environment is postulated via bypassing the containment building. This conveys a significant threat in severe accident management (SAM) for minimization of radionuclide release. To mitigate this risk, a numerical assessment of SAM strategies was performed for an SGTR accident of an Optimized Power Reactor 1000 MWe (OPR1000) using MELCOR code. Three in-vessel mitigation strategies were evaluated and the effect of delayed operation action was analyzed. The MELCOR calculations showed that activation of a prompt secondary feed and bleed (F&B) operation using auxiliary feed water and use of an atmospheric dump valve could prevent core degradation. However, depressurization using the safety depressurization system could not prevent core degradation, and the injection of coolant via high-pressure safety injection without the use of reactor coolant system (RCS) depressurization increased fission product release. When mitigation action was delayed by 30 minutes after SAMG entrance, a secondary F&B operation failed in depressurizing the RCS sufficiently, and a significant amount of fission products were released into the environment. These results suggest that appropriate mitigation actions should be applied in a timely manner to achieve the optimal mitigation effects.</P>
Evaluation of Two Types of Biosensors for Immunoassay of Botulinum Toxin
Choi, Kibong,Seo, Wonjun,Cha, Seunghee,Choi, Jungdo The Korea Science and Technology Center 1998 BMB Reports Vol.31 No.1
Immunoassay of botulinum toxin (BTX) B type was investigated using two types of biosensors: light addressable potentiometric sensor (LAPS) and surface plasmon resonance (SPR) sensor. Urease-tagged and immuno-filtration capture method have been used for LAPS. Tag-free and direct binding real-time detection method have been used for SPR sensor. The detection limit of sandwich assay format with LAPS was 10ng/ml, which was the lowest among methods tested. SPR has the advantage of being more convenient because Tag-free direct binding assay can be used and reaction time was reduced, regardless of low sensitivity. This result shows that sandwich assay format with LAPS can be used as an alternative method of BTX mouse bioassay which is known as the most sensitive method for the detection of BTX.
Choi, Jung-Woo,Chung, Won-Hyong,Lee, Kyung-Tai,Cho, Eun-Seok,Lee, Si-Woo,Choi, Bong-Hwan,Lee, Sang-Heon,Lim, Wonjun,Lim, Dajeong,Lee, Yun-Gyeong,Hong, Joon-Ki,Kim, Doo-Wan,Jeon, Hyeon-Jeong,Kim, Jiwoo Oxford University Press 2015 DNA research Vol.22 No.4
<P>Pigs have been one of the most important sources of meat for humans, and their productivity has been substantially improved by recent strong selection. Here, we present whole-genome resequencing analyses of 55 pigs of five breeds representing Korean native pigs, wild boar and three European origin breeds. 1,673.1 Gb of sequence reads were mapped to the Swine reference assembly, covering ∼99.2% of the reference genome, at an average of ∼11.7-fold coverage. We detected 20,123,573 single-nucleotide polymorphisms (SNPs), of which 25.5% were novel. We extracted 35,458 of non-synonymous SNPs in 9,904 genes, which may contribute to traits of interest. The whole SNP sets were further used to access the population structures of the breeds, using multiple methodologies, including phylogenetic, similarity matrix, and population structure analysis. They showed clear population clusters with respect to each breed. Furthermore, we scanned the whole genomes to identify signatures of selection throughout the genome. The result revealed several promising loci that might underlie economically important traits in pigs, such as the <I>CLDN1</I> and <I>TWIST1</I> genes. These discoveries provide useful genomic information for further study of the discrete genetic mechanisms associated with economically important traits in pigs.</P>
Effect of Molten Corium Behavior Uncertainty on the Severe Accident Progress
Choi, Wonjun,Kim, Taeseok,Jeon, Joongoo,Kim, Nam Kyung,Kim, Sung Joong Hindawi Limited 2018 Science and technology of nuclear installations Vol.2018 No.-
<P>Uncertainty of a severe accident code output needs to be handled reliably considering its use in safety regulation of nuclear industry. In particular, severe accident codes are utilized for probabilistic safety assessment (PSA), where the uncertainty of severe accident progress should be considered carefully due to its influence on human reliability analysis. Therefore, in this study, the uncertainty analysis of severe accident progress was performed using MELCOR code, and a total of 200 data sets of in-vessel uncertainty parameters were generated by Latin hypercube sampling method. The rank regression analysis was also performed to investigate the effect of uncertainty parameters on the severe accident progress. Sensitivity coefficients (SCs) in MELCOR such as molten clad drainage rate and zircaloy melt breakout temperature showed significant influence on relocation time and dryout time of lower plenum. However, the influence of uncertainty parameter diminished as the accident progressed.</P>