• Nuclear Engineering and Technology
• /
• v.53 no.3
• /
• pp.911-919
• /
• 2021

In this paper, the design stress intensity values for the plate-type fuel assembly for research reactor are presented. Through a tensile test, the material properties of the cladding (aluminum alloy 6061) and structural material (aluminum alloy 6061-T6), in this case the yield and ultimate tensile strengths, Young's modulus and the elongation, are measured with the temperatures. The empirical equations of the material properties with respect to the temperature are presented. The cladding undergoes several heat treatments and hardening processes during the fabrication process. Cladding strengths are reduced compared to those of the raw material during annealing. Up to a temperature of 150 ℃, the strengths of the cladding do not significantly decrease due to the dislocations generated from the cold work. However, over 150 ℃, the mechanical strengths begin to decrease, mainly due to recrystallization, dislocation recovery and precipitate growth. Taking into account the uncertainty of the 95% probability and 95% confidence level, the design stress intensities of the cladding and structural materials are established. The presented design stress intensity values become the basis of the stress design criteria for a safety analysis of plate-type fuels.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1796-1809
• /
• 2021

The subchannel of a research reactor used to generate high power density is designed to be narrow and rectangular and comprises plate-type fuels operating under downward flow conditions. Critical heat flux (CHF) is a crucial parameter for estimating the safety of a nuclear fuel; hence, this parameter should be accurately predicted. Here, machine learning is applied for the prediction of CHF in a narrow rectangular channel. Although machine learning can effectively analyze large amounts of complex data, its application to CHF, particularly for narrow rectangular channels, remains challenging because of the limited flow conditions available in existing experimental databases. To resolve this problem, we used four CHF correlations to generate pseudo-data for training an artificial neural network. We also propose a network architecture that includes pre-training and prediction stages to predict and analyze the CHF. The trained neural network predicted the CHF with an average error of 3.65% and a root-mean-square error of 17.17% for the test pseudo-data; the respective errors of 0.9% and 26.4% for the experimental data were not considered during training. Finally, machine learning was applied to quantitatively investigate the parametric effect on the CHF in narrow rectangular channels under downward flow conditions.

• Nuclear Engineering and Technology
• /
• v.53 no.3
• /
• pp.812-824
• /
• 2021

In order to reduce risks from the Steam Generator Tube Rupture (SGTR) accident and to meet safety targets, various measures have been analyzed to minimize the amount of fission product (FP) release. In this paper, we propose an introduction of a Containment Filtered Venting System (CFVS) connected to the steam generator secondary side, which can reduce the amount of FP release while minimizing adverse effects identified in the previous studies. In order to compare the effect of new equipment with the existing strategy, accident simulations using MELCOR were performed. As a result of simulations, it is confirmed that CFVS operation lowers FP release into the environment, and the release fractions are lower (minimum 0.6% of the initial inventory for Cs) than that of the strategy which intends to depressurize the primary system directly (minimum 15.2% for Cs). The sensitivity analyses identify that refill of the CFVS vessel is a dominant contributor reducing the amount of FP released. As the new strategy has the possibility of hydrogen combustion and detonation in CFVS, the installation of an igniter inside the CFVS vessel may be considered in reducing such hydrogen risk.

• Nuclear Engineering and Technology
• /
• v.53 no.1
• /
• pp.93-102
• /
• 2021

The analysis of the fluid flow characteristics in reactor pressure vessel is an important part of the hydraulic design of nuclear power plant, which is related to the structure design of reactor internals, the flow distribution at core inlet and the safety of nuclear power plant. The flow distribution and mixing characteristics in the pressurized reactor vessel for the 1000MWe advanced pressurized water reactor is analyzed by using Computational Fluid Dynamics (CFD) method in this study. The geometry model of the full-scaled reactor vessel is built, which includes the cold and hot legs, downcomer, lower plenum, core, upper plenum, top plenum, and is verified with some parameters in DCD. Under normal condition, it is found that the flow skirt, core plate holes and outlet pipe cause pressure loss. The maximum and minimum flow coefficient is 1.028 and 0.961 respectively, and the standard deviation is 0.019. Compared with other reactor type, it shows relatively uniform of the flow distribution at the core inlet. The coolant mixing coefficient is investigated with adding additional variables, showing that mass transfer of coolant occurs near the interface. The coolant mainly distributes in the 90° area of the corresponding core inlet, and mixes at the interface with the coolant from the adjacent cold leg. 0.1% of corresponding coolant is still distributed at the inlet of the outer-ring components, indicating wide range of mixing coefficient distribution.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1869-1877
• /
• 2021

This paper presents the neutron dose rate analysis of the new CONSTOR® RBMK-1500/M2 storage cask intended for the spent nuclear fuel storage at Ignalina Nuclear Power Plant in Lithuania. These casks are designed to be stored in a new "closed" type interim storage facility, with the capacity to store up to 202 CONSTOR® RBMK-1500/M2 casks. In 2016 y, the "hot trials" of this new facility were conducted and 10 CONSTOR® RBMK-1500/M2 casks loaded with the spent nuclear fuel were transported to the dedicated storage places in this facility. During "hot trials", the dose rate measurements of the CONSTOR® RBMK-1500/M2 casks were performed as the dose rate is one of the critical parameter to control and it must be below design (and safety) criteria. Therefore, having the actual data of the spent nuclear fuel characteristics, the neutron dose rate modeling of the CONSTOR® RBMK-1500/M2 cask loaded with this particular fuel was also performed. Neutron dose rate modeling was performed using MCNP 5 computer code with very detailed geometrical representation of the cask and the fuel. The obtained modeling results were compared with the measurement results and it was revealed, that modeling results are generally in good agreement with the measurements.

• Nuclear Engineering and Technology
• /
• v.53 no.2
• /
• pp.430-438
• /
• 2021

The spatial distribution of neutron flux or reaction rate was calculated by cell or mesh tally in traditional Monte Carlo simulation. However, either cell or mesh tally leads to the increase of memory consumption and simulation time. In this paper, the function expansion tally (FET) method was developed in Reactor Monte Carlo code RMC to solve this problem. The FET method was applied to the tallies of neutron flux distributions of uranium block and PWR fuel rod models. Legendre polynomials were used in the axial direction, while Zernike polynomials were used in the radial direction. The results of flux, calculation time and memory consumption of different expansion orders were investigated, and compared with the mesh tally. Results showed that the continuous distribution of flux can be obtained by FET method. The flux distributions were consistent with that of mesh tally, while the memory consumption and simulation time can be effectively reduced. Finally, the convergence analysis of coefficients of polynomials were performed, and the selection strategy of FET order was proposed based on the statistics uncertainty of the coefficients. The proposed method can help to determine the order of FET, which was meaningful for the efficiency and accuracy of FET method.

• The Journal of Korean Society for School & Community Health Education
• /
• v.22 no.3
• /
• pp.17-27
• /
• 2021

Objectives: As COVID-19 drags on, university students experience more stress and feel more anxious about their studies and career plans. Against the backdrop, this study aims to analyze the moderating effect of family health on the relationship between the spread of COVID-19 and the quality of life in university students. Methods: In order to achieve the purpose of this study, the results of an online survey performed with 216 university students in cities K and D were analyzed using frequency analysis, factor analysis, correlation analysis, regression analysis, and moderating effect analysis. Results: It was found that COVID-19 stress had a significant negative effect on the quality of life in university students, while family health showed a significant positive effect. In addition, the moderating effect of family health was statistically significant on the relationship between COVID-19 stress and the quality of life in university students. Conclusions: This study found that family health plays an essential role as a safety net in reducing stress and improve the quality of life in university students amid the social crisis of the COVID-19 pandemic. In this regard, it is required to develop various programs for communication with parents, including parent-child communication techniques.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.20 no.6
• /
• pp.145-150
• /
• 2020

The importance of managing blind spots in the welfare crisis is increasing. Accordingly, in order to manage the blind spot of the welfare crisis, it is necessary to manage the social safety net with the contents of supporting income and self-reliance of low-income families, and actively discovering and supporting poor and crisis households. In this paper, we reviewed various problems related to blind spots for the management of welfare blind spots, and proposed the applicability of blockchain-based distributed ID and the possibility of distributed ID technology in stages by considering the range of blind spots.

• Journal of Korean society of Dental Hygiene
• /
• v.21 no.3
• /
• pp.211-225
• /
• 2021

Objectives: To validate the role of a new information and communication technology platform that we created for the betterment of the oral health of persons with disabilities and for providing appropriate health care services. Methods: A Delphi survey was conducted among 16 people in various professions, including academia, government agencies, and dentistry, to evaluate the validity of the information and communication technology platform. Moreover, platform satisfaction was evaluated using a user experience questionnaire among 200 people, including persons with disabilities, parents, and public institutions. Results: Experts in consensus indicated a high validity for the categories of service provider (CV=0.29, CVR=0.69), service target (CV=0.29, CVR=0.38), service contests (CV=0.27, CVR=0.63), and financial support (CV=0.30, CVR=0.63) in our information and communication technology platform. In addition, information from questionnaires on user experience and communication technology satisfaction analysis showed that both users and providers were highly satisfied with the platform. Conclusions: The provision of oral health services based on the new information and communication technology platform has numerous advantages, in addition to providing adequate oral health care for the disabled. Furthermore, the social safety net for improved oral health may be further strengthened.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.8
• /
• pp.117-126
• /
• 2021

The increasing number of retrenchments because of the current global pandemic, Covid-19, has led many to shift to the digital economy, especially among the low-income group (B40) in Malaysia. Crowdsourcing is the collection of information, opinions, or work from a group of people, usually sourced via the Internet. Fueled by the development of Internet-based platforms that provided its technological foundation, and the need for an agile and uniquely skilled workforce, crowdsourcing has grown from the grassroots, with a burgeoning body of research investigating its many aspects. However, very few studies examined crowd workers' motivation for continuous participation on online crowdsourcing platforms. Thus, this paper aims to explore the technological factors that facilitate B40's group motivation in Malaysia to continue to participate in online crowdsourcing platforms. This paper employed a qualitative approach, using a semi-structured interview. The thematic analysis method was used to decode the data extracted from the interview transcript. The finding of this study identified four main themes and seven sub-themes: (1) Technology efficacy, (2) Platform Management: client-worker management, safety net, payment mechanism, (3) Platform Design: UI design, rating feature and (4) Infrastructure: Internet connection, technology infrastructure. This study can provide a guideline for managing crowdsourcing practices in Malaysia, especially for the crowdsourcing platform developer.