• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.469-476
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• 2013

In a postulated severe core damage accident in a PHWR, multiple failures of core cooling systems may lead to the collapse of pressure tubes and calandria tubes, which may ultimately relocate inside the calandria vessel forming a terminal debris bed. The debris bed, which may reach high temperatures due to the decay heat, is cooled by the moderator in the calandria. With time, the moderator is evaporated and after some time, a hot dry debris bed is formed. The debris bed transfers heat to the calandria vault water which acts as the ultimate heat sink. However, the questions remain: how long would the vault water be an ultimate heat sink, and what would be the failure mode of the calandria vessel if the heat sink capability of the reactor vault water is lost? In the present study, a numerical analysis is performed to evaluate the thermal loads and the stresses in the calandria vessel following the above accident scenario. The heat transfer from the molten corium pool to the surrounding is assumed to be by a combination of radiation, conduction, and convection from the calandria vessel wall to the vault water. From the temperature distribution in the vessel wall, the transient thermal loads have been evaluated. The strain rate and the vessel failure have been evaluated for the above scenario.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.12
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• pp.305-311
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• 2021

The purpose of this study is to examine and analyze product innovation and process innovation as an indicator of innovation that affects the performance of small and medium enterprises (SMEs). Government policy as a moderator of the effect of innovation on performance. This research was conducted during the COVID-19 pandemic. The population in this study are SMEs that produce clothes and t-shirts in Indonesia. Data collection is done through questionnaires and direct interviews. Online questionnaires were given to the managers and business owners. The sampling technique used is purposive sampling based on certain conditions of the research object, and in this study 100 business units were selected. The result of loading factor correlation between indicator and latent construct is significant. Hypothesis which explored the linear relationship between the construct variables was tested. Structural Equation Modeling (SEM) was used. The results of this study indicate that there is a positive relationship between innovation and business performance, and government policies have an important role as a full moderator in this relationship. The study findings concluded that the government policies are an important instrument in supporting the development of SMEs by innovating product and process innovation.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1314-1321
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• 2019

In case of multiple failure scenario, such as LOCA with ECCS failure, the decay heat continues to raise the reactor core temperature, eventually leading to the core voiding. In such scenario the convective heat transfer becomes poor and the majority of the heat transfer from fuel bundle takes place by radiation mode. During this abnormal working condition, if the channel pressure is less than 1 MPa, the PT sags and come in contact with the CT. This results in high rate of heat transfer from contact location to moderator. The present paper aims to capture the temperature profile over a simulated nuclear channel during such scenario at a steady state temperature of $600^{\circ}C$ (Centre pin) at two different configurations of PT i.e. PT concentric with CT and PT contact with CT. The results showed that the bottom nodes of all the components (Fuel bundle, PT and CT) of the simulated channel was greatly influenced by the PT/CT contact. Moreover, higher temperature were observed at top nodes of the PT and outer pins of the fuel bundle. However, no significant variation in temperatures were obtained in fuel bundle and CT in concentric condition.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.1
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• pp.851-861
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• 2021

The main objective of this study is to examine the government ownership effect on the United Arab Emirates (UAE) firm's corporate social responsibility (CSR). Government ownership is assumed to affect the CSR either directly or indirectly. That is by moderating the association between corporate governance and CSR. Publicly listed companies on the UAE capital markets (Abu Dhabi and Dubai) from 2010-2013 constituted the study sample. Panel data regression analyses and random effect model is used to examine the effects of board size, board independence, and audit committee characteristics on CSR. Government ownership is used as a moderator variable. The result showed that the existence of government ownership has a moderator effect on the association between corporate governance mechanisms and the CSR. Precisely, the research revealed that the audit committee characteristics become more effective in improving the firm's CSR when the government owns shares in the organization. The main contribution of this study is to examine how firm ownership structure influences good corporate governance and CSR in the UAE. The study contributes to the CSR literature by merging between the existence of governmental ownership and the power to enforce the implementation of corporate governance in an emerging country.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.1205-1215
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• 2021

The study's purpose is to assess how board chairman tenure (BCT) contributes to limiting the earnings management practices (EM) in Iraqi banks. We compare the direct influence of the corporate governance mechanisms (CG) on EM practices and use BCT as a moderator that affects the influence of CG on EM. The sample of the study is the financial' firms listed on the Iraqi Stock Exchange for the period 2013-2018. Using purposive sampling data was collected from annual reports and data stream. We use the random effect model in panel data regression by using Stata to analyze the data. Findings proved that CG mechanisms insignificantly influence EM, except the meeting frequency was significant. By contrast, BCT had a positive and considerable influence as the moderating variable between CG and EM. These results suggested that the Chairman's tenure on the board lead to enhanced governance mechanisms to limit the EM practice in Iraqi financial firms. Accordingly, this study is one of the few studies in the Iraq environment that examine the influence of CG mechanisms on EM practices, in addition to examining the BCT as a moderator between CG and EM, thus, filling the gap in such studies in developing countries.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.877-887
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• 2022

A new reactor concept is described that directly couples a supercritical CO₂ (sCO₂) power cycle with a CO₂-cooled, heavy water moderated pressure tube core. This configuration attains the simplification and economic potential of past direct-cycle sCO₂ concepts, while also providing safety and power density benefits by using the moderator as a heat sink for decay heat removal. A 200 MWe design is described that heavily leverages existing commercial nuclear technologies, including reactor and moderator systems from Canadian CANDU reactors and fuels and materials from UK Advanced Gas-cooled Reactors (AGRs). Descriptions are provided of the power cycle, nuclear island systems, reactor core, and safety systems, and the results of safety analyses are shown illustrating the ability of the design to withstand large-break loss of coolant accidents. The resulting design attains high efficiency while employing considerably fewer systems than current light water reactors and advanced reactor technologies, illustrating its economic promise. Prospects for the design are discussed, including the ability to demonstrate its technologies in a small (~20 MWe) initial system, and avenues for further improvement of the design using advanced technologies.

• Journal of the Korea Safety Management & Science
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• v.25 no.2
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• pp.175-185
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• 2023

Prior studies focusing on safety behavior have not given sufficient consideration to the potential impact exerted by different leadership styles. Of these various styles, my attention is specifically drawn to the influence of ethical leadership on safety behavior. In this paper, I delve into the influence of ethical leadership on safety behavior, shedding light on both the underlying mechanisms(mediators) and a significant contextual factor(moderator). I probe into the successive mediating roles of employees' trust in the organization and their commitment to it, within the context of the relationship between ethical leadership and safety behavior. Further, I posit that authentic leadership positively adjusts the connection between ethical leadership and organizational trust. My findings underscore that ethical leadership enhances employee safety behavior, facilitated by the chain mediation of trust in the organization and organizational commitment. Moreover, I discover that authentic leadership, as a positive moderator, magnifies the favorable impact of ethical leadership on organizational trust. This paper will also articulate the theoretical implications, practical applications, and limitations of the study.

• Journal of the Korean Society of Systems Engineering
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• v.19 no.2
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• pp.46-58
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• 2023

Deterministic safety analysis is a crucial part of safety assessment, particularly when it comes to demonstrating the safety of nuclear power plant designs. The traditional approach to deterministic safety analysis models is to model the nuclear core using point kinetics. However, this simplified approach does not fully reflect the real core behavior with proper moderator and fuel reactivity feedbacks during the transient. The use of Multi-Physics approach allows more precise simulation reflecting the inherent three-dimensionality (3D) of the problem by representing the detailed 3D core, with instantaneous updates of feedback mechanisms due to changes of important reactivity parameters like fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC). This paper addresses a CEA ejection accident at hot full power (HFP), in which the underlying strong and un-symmetric feedback between thermal-hydraulics and reactor kinetics exist. For this purpose, a multi-physics analysis tool has been selected with the nodal kinetics code, 3DKIN, implicitly coupled to the thermal-hydraulic code, RELAP5, for real-time communication and data exchange. This coupled approach enables high fidelity three-dimensional simulation and is therefore especially relevant to reactivity initiated accident (RIA) scenarios and power distribution anomalies with strong feedback mechanisms and/or un-symmetrical characteristics as in the CEA ejection accident. The Systems Engineering approach is employed to provide guidance in developing the work in a systematic and efficient fashion.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4685-4694
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• 2023

The ability to calculate the material density sensitivity coefficients of power with respect to the material density has broad application prospects for accelerating Monte Carlo-Thermal Hydraulics iterations. The second-order material density sensitivity coefficients for the general Monte Carlo score have been derived based on the differential operator sampling method in this paper, and the calculation of the sensitivity coefficients of cell power scores with respect to the material density has been realized in continuous-energy Monte Carlo code RMC. Based on the power-density sensitivity coefficients, the sensitivity coefficients of power scores to some other physical quantities, such as power-boron concentration coefficients and power-temperature coefficients considering only the thermal expansion, were subsequently calculated. The effectiveness of the proposed method is demonstrated in the power-density coefficients problems of the pressurized water reactor (PWR) moderator and the heat pipe reactor (HPR) reflectors. The calculations were carried out using RMC and the ENDF/B-VII.1 neutron nuclear data. It is shown that the calculated sensitivity coefficients can be used to predict the power scores accurately over a wide range of boron concentration of the PWR moderator and a wide range of temperature of HPR reflectors.

• Journal of Radiation Protection and Research
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• v.22 no.2
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• pp.119-125
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• 1997

PHWR achieves high neutron economy by adopting heavy water as its moderator and coolant. On the other hand it permits much tritium generation, compared to LWR, due to the neutron capture reaction of deuterium in heavy water. Meanwhile in the reactor core, $^3He formed as the result of-decay of tritium, captures a thermal neutron and transforms to tritium again. The existing calculation models on tritium generation in PHWR neglect the contribution of $^3He$ in both moderator and coolant due to its relatively low solubility. However the neutron capture cross-section of $^3He$ is almost $1.6{\times}10^7$ times as large as that of deuterium. That means that the dissolved amount of 0.03 ppm of $^3He$ in heavy water is enough to generate the same amount of tritium as that generated by the deuterium of total heavy water in the system. This study dealt with the contribution of $^3He$ to tritium generation. As a sample case, the contribution of $^3He$ to the tritium generation in Wolsong #1 was evaluated and compared to the measured values. According to the result of this study, it is concluded that $^3He$ in coolant contributes very much to the tritium generation but that in moderator shows negligible effects due to the low solubility and $^4He$ cover gas. At the beginning of the plant operation, the contribution of $^3He$ is slightly greater than the measured value but agrees well with the measured as the operating time increases.