• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.41 no.4
• /
• pp.171-178
• /
• 2018

Recently, the continuing operation of nuclear power plants has become a major controversial issue in Korea. Whether to continue to operate nuclear power plants is a matter to be determined considering many factors including social and political factors as well as economic factors. But in this paper we concentrate only on the economic factors to make an optimum decision on operating nuclear power plants. Decisions should be based on forecasts of plant accident risks and large and small accident data from power plants. We outline the structure of a decision model that incorporate accident risks. We formulate to decide whether to shutdown permanently, shutdown temporarily for maintenance, or to operate one period of time and then periodically repeat the analysis and decision process with additional information about new costs and risks. The forecasting model to predict nuclear power plant accidents is incorporated for an improved decision making. First, we build a one-period decision model and extend this theory to a multi-period model. In this paper we utilize influence diagrams as well as decision trees for modeling. And bayesian statistical approach is utilized. Many of the parameter values in this model may be set fairly subjective by decision makers. Once the parameter values have been determined, the model will be able to present the optimal decision according to that value.

• Nuclear Engineering and Technology
• /
• v.54 no.10
• /
• pp.3878-3887
• /
• 2022

For the future energy-mix policy for carbon neutrality, demand for the capability of load-follow operation has emerged in nuclear power plants in order to accommodate the intermittency of renewable energy. The short-term decay heat analysis is also required to evaluate the decay heat level varied by the power level change during the load-follow operation, which is a very important parameter in terms of short-term decay heat removal during a grace time. In this study, the short-term decay heat level for 10 days after the shutdown was evaluated for both seasonal and daily load-follow cases. Additionally, the nuclide-wise contribution to the accumulated decay heat for 10 days was analyzed for further understanding of the short-term decay heat behavior. The result showed that in the seasonal case, the decay heat level was mainly determined by the power level right before the shutdown and the amount of each nuclide was varied with the power variation due to the long variation interval of 90 days. Whereas, in the daily case, the decay heat level was strongly impacted by the average power level during operation and meaningful mass variations for those nuclides were not observed due to the short variation interval of 0.5 days.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.3
• /
• pp.96-102
• /
• 2009

This paper deals with gate drive and power IC for high power devices(600V/200A and 1200V/150A). The proposed gate driver provides high gate driving capability (4 A source, 8 A sink), and over-current protected by means of power transistor desaturation detection. In addition, soft-shutdown function is added to reduce voltage overshoots due to parasitic inductance. This gate drive If is designed, fabricated, and tested using the Dongbu hitek 0.35um BCDMOS process.

• Journal of Korean Society for Atmospheric Environment
• /
• v.34 no.5
• /
• pp.687-696
• /
• 2018

In order to develop effective emission abatement strategies for coal-fired power plants, we analyzed the shutdown effects of coal-fired power plants on $PM_{2.5}$ concentration in June by employing air quality model for the period from 2013 to 2016. WRF (Weather Research and Forecast) and CMAQ(Community Multiscale Air Quality) models were used to quantify the impact of emission reductions on the averaged $PM_{2.5}$ concentrations in June over Chungcheongnam-do area in Korea. The resultant shutdown effects showed that the averaged $PM_{2.5}$ concentration in June decreased by 1.2% in Chungcheongnam-do area and decreased by 2.3% in the area where the surface air pollution measuring stations were located. As a result of this study, it was confirmed that it is possible to analyze policy effects considering the change of meteorology and emission and it is possible to quantitatively estimate the influence at the maximum impact region by utilizing the air quality model. The results of this study are expected to be useful as a basic data for analyzing the effect of $PM_{2.5}$ concentration change according to future emission changes.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.10 no.1
• /
• pp.31-36
• /
• 2014

For decreasing an unexpected shutdown of Nuclear Power Plants, Korea Hydro & Nuclear Power co.(KHNP) has developed Single Point Vulnerability(SPV) of NPPs since 2008. SPV is the equipment that cause reactor shutdown & turbine trip or more than 50% power rundown due to its malfunction. New type Nuclear Power Plants need to develop the SPV list, so performed the SPV selection for about 1 year. To develop this, Failure Mode Effect Analysis(FMEA) methods are used. As results of FMEA analysis, about 700 equipment are selected as SPV. Thereafter those are going to be applied to new type Nuclear Power Plants to enhance equipment reliability.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.4
• /
• pp.509-512
• /
• 2012

For decreasing an unexpected shutdown of Nuclear Power Plants, Korea Hydro & Nuclear Power co.(KHNP) has developed Single Point Vulnerability(SPV) of NPPs since 2008. SPV is the equipment that cause reactor shutdown & turbine trip or more than 50% power rundown due to its malfunction. Newly built Nuclear Power Plants need to develop the SPV list, so performed the job which analyse equipment failure effect for SPV selection for 1 year. To develop this, Failure Mode Effect Analysis(FMEA) and Fault Tree Analysis(FTA) methods are used. As results of this analysis, about 900 equipment are selected as SPV. Thereafter those are going to be applied to Nuclear Power Plants to enhance equipment reliability.

• Nuclear Engineering and Technology
• /
• v.52 no.3
• /
• pp.654-659
• /
• 2020

The reliability of the spent fuel pool instrument is very important for the security of nuclear power plant, especially during the earthquake. The effect of the fluid force on the vibration characteristics of the flexible tube of the spent fuel pool instrument needs comprehensive analysis. In this paper, based on the potential flow theory, the hydrodynamic pressures acting on the flexible tube were obtained. A mathematical model of a flexible tube was constructed to obtain the dynamic response considering the effects of seismic load and fluid force, and a computer code was written. Based on the mathematical model and computer code, the maximum stresses of the flexible tube in both safe shutdown earthquake and operating basis earthquake events on the spent fuel pool with three typical water levels were calculated, respectively. The results show that the fluid force has an obvious effect on the stress and strain of the flexible tube in both safe shutdown earthquake and operating basis earthquake events.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.480-485
• /
• 2011

In this study, the seismic analysis of power plant piping system was performed using finite element model. This study was performed by ANSYS 12.1. For qualification of power plant piping system, the response spectrum analysis was performed using the given operating basis earthquake(OBE) and safe shutdown earthquake(SSE) floor response spectrum. The maximum stresses of power plant piping system were 166 MPa under OBE condition and 281 MPa under SSE condition. Thus, it can shown that the structural integrity of tpower plant piping system has a stable structure for seismic load conditions.

• Nuclear Engineering and Technology
• /
• v.56 no.3
• /
• pp.1022-1028
• /
• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• Nuclear Engineering and Technology
• /
• v.30 no.4
• /
• pp.342-352
• /
• 1998

A nuclear design feasibility of soluble boron free(SBF core for the medium-sized(600MWe) PWR was investigated. The result conformed that soluble boron free operation could be performed by using current PWR proven technologies. Westinghouse advanced reactor, AP-600 was chosen as a design prototype. Design modification was applied for the assembly design with burnable poison and control rod absorber material. In order to control excess reactivity, large amount of gadolinia integral burnable poison rods were used and B4C was used as a control rod absorber material. For control of bottom shift axial power shape due to high temperature feedback in SBF core, axial zoning of burnable poison was applied to the fuel assemblies design. The combination of enrichment and rod number zoning for burnable poison could make an excess reactivity swing flat within around 1% and these also led effective control on axial power offset and peak pin power, The safety assessment of the designed core was peformed by the calculation of MTC, FTC and shutdown margin. MTC in designed SBF core was greater around 6 times than one of Ulchin unit 3&4. Utilization of enriched BIO(up to 50w1o) in B4C shutdown control rods provided enough shutdown margin as well as subcriticality at cold refueling condition.