• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1120-1125
• /
• 2004

Welding characteristics of STS304 stainless steel and Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. Alloy 600 being used in steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion environment, stress corrosion cracking can occur on this material. Presented here are the results from a series of experiments in which dissimilar metal welds were made using the gas tungsten arc welding process with pure argon shielding gas. But It is well known that solidification cracking susceptibility of austenitic alloys depends on the solidification temperature range and amount/distribution of solute rich liquid that exists at the terminal stages of solidification. An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent welding zone formation at dissimilar metal welds.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
• /
• pp.100-103
• /
• 2004

This paper presents the aspect and distribution of voltage and current harmonics being made at low voltage power systems. The voltage and current harmonics in power systems supplying various loads were monitored and analyzed. We have examined the results compared to advanced countries' harmonics control standards. As a result, the current harmonics were significantly greater than the voltage harmonics. In particular, the harmonics of currents flowing through loads with power switching electronics was pronounced. Also, the contents of current harmonics of street lamp circuits was about 30%, and it was decreased to 12.3% with the installation of series reactor. On the whole, The measured results of voltage and current harmonics exceeds the regulation limits recommended by IEEE 519-1992.

• 대한전기학회논문지
• /
• 제34권3호
• /
• pp.115-123
• /
• 1985

A two phase chopper system with two separate groups of DC motors for regenerative braking is dealt with in this article. The main circuit consists of two sets of chopping parts, four diodes and two separate groups of DC motors. Although the proposed chopper circuit requires more circuit elements than the conventional two phase chopper system with combined output, it has the following advantages`(1). Ripple frequency of smoothing reactor current becomes twice as high as that of the conventional system, so the continuous current range and the ripple ratio are improved greatly. Therefore, the efficiency becomes even higher, the capacity of commutation equipment is reduced and the inductive interference become less.(2). Load current division becomes equalized. Therefore it is possible to drive not only series motors but also shunt, separately excited and compound motors.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1219-1221
• /
• 2005

We improved quench properties of a superconducting fault current limiter(SFCL) components based on YBCO thin films. This consists of three components with nearly identical properties and one with slightly difference properties. The units were connected in series and first of parallel to increase the current and voltage ratings. It have caused significantly imbalanced power distribution. The imbalance remarkably improved by connecting a shunt reactor to the SFCL component in parallel.

• Nuclear Engineering and Technology
• /
• 제45권4호
• /
• pp.459-468
• /
• 2013

During a station blackout (SBO), the initiating event is a loss of Class IV and Class III power, causing the loss of the pumps, used in systems such as the primary heat transporting system (PHTS), moderator cooling, shield cooling, steam generator feed water, and re-circulating cooling water. The reference case of the SBO case does not credit any of these active heat sinks, but only relies on the passive heat sinks, particularly the initial water inventories of the PHTS, moderator, steam generator secondary side, end shields, and reactor vault. The reference analysis is followed by a series of sensitivity cases assuming certain system availabilities, in order to assess their mitigating effects. This paper also establishes the strategies to mitigate SBO accidents. Current studies and strategies use the computer code of the Integrated Severe Accident Analysis Code (ISAAC) for Wolsong plants. The analysis results demonstrate that appropriate strategies to mitigate SBO accidents are established and, in addition, the symptoms of the SBO processes are understood.

• Nuclear Engineering and Technology
• /
• 제55권8호
• /
• pp.3010-3016
• /
• 2023

In recent years, the development of radioactive waste containers for nuclear facility decommissioning and dismantling is a critical issue because the Taiwan domestic boiling water reactor nuclear power plant is going to be decommissioned. The main purpose of this research is to design a metal container that meets the structural requirements of related regulations. At first, the shielding analysis was performed by varying dimensions of radioactive waste to determine the storage efficiency of the container. Then, a series of structural analyses for operational and accidental conditions of the container with full load were conducted, such as lifting, stacking, and drop impact conditions. On the other hand, the field drop impact tests were carried out to ensure structural integrity. The present research demonstrates the structural safety of the developed container for decommissioned nuclear facilities in Taiwan.

• 한국대기환경학회지
• /
• 제30권6호
• /
• pp.577-585
• /
• 2014

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and $V_2O_5$ were supported on ${\gamma}-Al_2O_3$. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of $V_2O_5/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of $V_2O_5/{\gamma}-Al_2O_3$ > ${\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with $V_2O_5/{\gamma}-Al_2O_3$, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: $1.0Lmin^{-1}$; SIE: ${\sim}355JL^{-1}$).

• Nuclear Engineering and Technology
• /
• 제52권7호
• /
• pp.1429-1435
• /
• 2020

Applying an accurate parametric prediction model to identify abnormal or false pressurizer water levels (PWLs) is critical to the safe operation of marine pressurized water reactors (PWRs). Recently, deep-learning-based models have proved to be a powerful feature extractor to perform high-accuracy prediction. However, the effectiveness of models still suffers from two issues in PWL prediction: the correlations shifting over time between PWL and other feature parameters, and the example imbalance between fluctuation examples (minority) and stable examples (majority). To address these problems, we propose a cost-sensitive mechanism to facilitate the model to learn the feature representation of later examples and fluctuation examples. By weighting the standard mean square error loss with a cost-sensitive factor, we develop a Cost-Sensitive Long Short-Term Memory (CSLSTM) model to predict the PWL of PWRs. The overall performance of the CSLSTM is assessed by a variety of evaluation metrics with the experimental data collected from a marine PWR simulator. The comparisons with the Long Short-Term Memory (LSTM) model and the Support Vector Regression (SVR) model demonstrate the effectiveness of the CSLSTM.

• Journal of Radiation Protection and Research
• /
• 제39권4호
• /
• pp.176-181
• /
• 2014

The object of this paper is to evaluate the fission product inventories and radiological doses in a non-LOCA event, based on the U.S. NRC's regulatory methodologies recommended by the TID-14844 and the RG 1.195. For choosing a non-LOCA event, one fuel assembly was assumed to be melted by a channel blockage accident. The Hanul nuclear power reactor unit 6 and the CE $16{\times}16$ fuel assembly were selected as the computational models. The burnup cross section library for depletion calculations was produced using the TRITON module in the SCALE6.1 computer code system. Based on the recently licensed values for fuel enrichment and burnup, the source term calculation was performed using the ORIGEN-ARP module. The fission product inventories released into the environment were obtained with the assumptions of the TID-14844 and the RG 1.195. With two kinds of source terms, the radiological doses of public in normal environment reflecting realistic circumstances were evaluated by applying the average condition of meteorology, inhalation rate, and shielding factor. The statistical analysis was first carried out using consecutive three year-meteorological data measured at the Hanul site. The annual-averaged atmospheric dispersion factors were evaluated at the shortest representative distance of 1,000 m, where the residents are actually able to live from the reactor core, according to the methodology recommended by the RG 1.111. The Korean characteristic-inhalation rate and shielding factor of a building were considered for a series of dose calculations.

• Nuclear Engineering and Technology
• /
• 제50권1호
• /
• pp.43-53
• /
• 2018

It is important to clarify the characteristics of flow regimes underlying the debris bed formation behavior that might be encountered in core disruptive accidents of sodium-cooled fast reactors. Although in our previous publications, by applying dimensional analysis technique, an empirical model, with its reasonability confirmed over a variety of parametric conditions, has been successfully developed to predict the regime transition and final bed geometry formed, so far this model is restricted to predictions of debris mixtures composed of spherical particles. Focusing on this aspect, in this study a new series of experiments using nonspherical particles have been conducted. Based on the knowledge and data obtained, an extension scheme is suggested with the purpose of extending the base model to cover the particle-shape influence. Through detailed analyses and given our current range of experimental conditions, it is found that, by coupling the base model with this scheme, respectable agreement between experiments and model predictions for the regime transition can be achieved for both spherical and nonspherical particles. Knowledge and evidence from our work might be utilized for the future improvement of design of an in-vessel core catcher as well as the development and verification of sodium-cooled fast reactor severe accident analysis codes in China.