• Title/Summary/Keyword: power shutdown

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Dynamic Analysis of Diesel Generators on Starting Large Induction Motors (대용량유도전동기 기동시의 비상용 디젤발전기 동특성 해석)

  • Han, Poong;Cho, Sung-Don
    • Proceedings of the KIEE Conference
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    • 1987.11a
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    • pp.139-142
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    • 1987
  • It is important to evaluate the voltage characteristics of diesel generator as an emergency power supply in nuclear power plant. On loss of offsite power sources, emergency safeguard loads required to safely shutdown the reactor should be supplied by diesel generator. This paper presents the dynamic stability program to evaluate diesel generator performance as an emergency power system. The results Indicate the diesel generator ability to start the motors successfully seems to life in its impedances and inertias.

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A study on the improvement of Auxiliary Power Unit auto-shutdown of T-50 series aircraft based on analysis of ECU response characteristics (ECU 응답특성 분석을 통한 T-50 계열 항공기 보조동력장치 자동 꺼짐 개선에 관한 연구)

  • Park, Sung-Jae;Yoo, In-Je;Choi, Su-Jin;Lee, Dong-Ki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.3
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    • pp.640-646
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    • 2017
  • A GEN TEST of the auxiliary power unit of a T-50 series aircraft is performed as part of the operational test of its emergency power system on the ground before flight. At this time, the auxiliary power unit should be automatically turned off via the response signal of the ECU when power is not normally supplied to the emergency power system. If the correct operation of the emergency power system cannot be confirmed on the ground, it is not possible to proceed with the flight. This kind of defect is a major factor causing the operation rate of the aircraft to be decreased. The defect code identified by the ECU was confirmed as a defect in the inverter. However, the same defect was found after replacing the inverter. This report presents an improved method of identifying the cause of the defect by analyzing the response characteristics of the ECU and emergency power system and allows the ECU to be recognized as the cause of the defect if the inverter does not generate a voltage within a certain time. Also, the application of the improved method confirmed that it can satisfy the output request time of the emergency power system and effectively prevent the auto-shutdown of the auxiliary power unit.

Vital Area Identification for the Physical Protection of Nuclear Power Plants during Low Power and Shutdown Operation (원자력발전소 정지저출력 운전 기간의 물리적방호를 위한 핵심구역파악)

  • Kwak, Myung Woong;Jung, Woo Sik;Lee, Jeong-ho;Baek, Min
    • Journal of the Korean Society of Safety
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    • v.35 no.1
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    • pp.107-115
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    • 2020
  • This paper introduces the first vital area identification (VAI) process for the physical protection of nuclear power plants (NPPs) during low power and shutdown (LPSD) operation. This LPSD VAI is based on the 3rd generation VAI method which very efficiently utilizes probabilistic safety assessment (PSA) event trees (ETs). This LPSD VAI process was implemented to the virtual NPP during LPSD operation in this study. Korea Atomic Energy Research Institute (KAERI) had developed the 2nd generation full power VAI method that utilizes whole internal and external (fire and flooding) PSA results of NPPs during full power operation. In order to minimize the huge burden of the 2nd generation full power VAI method, the 3rd generation full power VAI method was developed, which utilizes ETs and minimal PSA fault trees instead of using the whole PSA fault tree. In the 3rd generation full power VAI method, (1) PSA ETs are analyzed, (2) minimal mitigation systems for avoiding core damage are selected from ETs by calculating system-level target sets and prevention sets, (3) relatively small sabotage fault tree that has the systems in the shortest system-level prevention set is composed, (4) room-level target sets and prevention sets are calculated from this small sabotage fault tree, and (5) the rooms in the shortest prevention set are defined as vital areas that should be protected. Currently, the 3rd generation full power VAI method is being employed for the VAI of Korean NPPs. This study is the first development and application of the 3rd generation VAI method to the LPSD VAI of NPP. For the LPSD VAI, (1) many LPSD ETs are classified into a few representative LPSD ETs based on the functional similarity of accident scenarios, (2) a few representative LPSD ETs are simplified with some VAI rules, and then (3) the 3rd generation VAI is performed as mentioned in the previous paragraph. It is well known that the shortest room-level prevention sets that are calculated by the 2nd and 3rd generation VAI methods are identical.

Applicability Evaluation of Methodology for Evaluating High Cycle Thermal Fatigue of a Mixing Tee in Nuclear Power Plants (원전 혼합배관 고주기 열피로 평가방법론의 적용성 평가)

  • Kim, Sun-Hye;Sung, Hee-Dong;Choi, Jae-Boong;Huh, Nam-Su;Park, Jeong-Soon;Choi, Young-Hwan
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.7 no.4
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    • pp.44-50
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    • 2011
  • Turbulent mixing of hot and cold coolants is one of the possible causes of high cycle thermal fatigue in piping systems of nuclear power plants. A typical situation for such mixing appears in turbulent flow through a T-junction. Since the high cycle thermal fatigue caused by thermal striping was not considered in the piping fatigue design in several nuclear power plants, it is very important to evaluate the effect of thermal striping on the integrity of mixing tees. In the present work, before conducting detailed evaluation, three thermal striping evaluation methodology suggested by EPRI, JSME and NESC are analyzed. Then, a by-pass pipe connected to the shutdown cooling system heat exchanger is investigated by using these evaluation methodology. Consequently, the resulting thermal stresses and the fatigue life of the mixing tee are reviewed and compared to each other. Futhermore, the limitation of each methodology are also presented in this paper.

Present State Analysis of Customers' Effect in Power Distribution System by Momentary Voltage Variation (배전계통의 순시전압변동에 의한 수용가측 영향의 현황 분석)

  • 김재철;윤상윤;오정환;임성정
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.12 no.4
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    • pp.37-46
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    • 1998
  • This paper analyzes the present state of customers' effect in distribution system by momentary voltage variation. Customers are becoming increasingly concerned about the quality of electric power. Most of all, the voltage magnitude quality is very important because it can have a direct effect on customers. Especially, according to the development of automatic process, momentary voltage variations result in the shutdown of sensitive loads such as electronic equipment, computer and magnetic contactor, and so on. To analyze the shutdown rate of customers' equipments by the momentary voltage variation, we present the CVEMA curve and he cumulative CVEA curve of each load type through the experiment for the customers' sensitive equipments. Also, we have surveyed customers' opinion by the questionnaire as "Survey of Power Quality" an then the results are reported.

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Innovative technologies for spent fuel safe management at Ignalina channel-type reactors

  • Babilas, Egidijus;Dokucajev, Pavel;Janulevicius, Darius;Markelov, Aleksej;Pabarcius, Raimondas;Rimkevicius, Sigitas;Uspuras, Eugenijus;Vaisnoras, Mindaugas
    • Nuclear Engineering and Technology
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    • v.50 no.3
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    • pp.504-511
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    • 2018
  • In Lithuania, all spent nuclear fuel (SNF) resulted from the operation of the Ignalina Nuclear Power Plant (INPP), which had two Russian Acronym for "Channelized Large Power Reactor"-type reactors. After the final shutdown, the total amount of SNF at the INPP was approximately 22,000 fuel assemblies. All these assemblies will be stored for about 50 years and disposed of after that. The decision to shut down and decommission both reactors in Lithuania before termination of design period raises a significant challenge for the treatment of accumulated SNF. Therefore, various techniques and technologies for SNF management were developed and justified for that specific case, and a set of special equipment was installed at the INPP, the effectiveness of which was demonstrated during its operation. This article presents unique techniques related to the management of SNF adopted and commissioned at the INPP after its operation shutdown, namely fuel rod cladding leak tightness control system and special equipment for collection of possible spillage during handling of SNF assembly in the hot cell. The operational experience and measurement results of fuel rod cladding leak tightness control system are presented.

Technical note: Estimation of Korean industry-average initiating event frequencies for use in probabilistic safety assessment

  • Kim, Dong-San;Park, Jin Hee;Lim, Ho-Gon
    • Nuclear Engineering and Technology
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    • v.52 no.1
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    • pp.211-221
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    • 2020
  • One fundamental element of probabilistic safety assessment (PSA) is the initiating event (IE) analysis. Since IE frequencies can change over time, time-trend analysis is required to obtain optimized IE frequencies. Accordingly, such time-trend analyses have been employed to estimate industry-average IE frequencies for use in the PSAs of U.S. nuclear power plants (NPPs); existing PSAs of Korean NPPs, however, neglect such analysis in the estimation of IE frequencies. This article therefore provides the method for and results of estimating Korean industry-average IE frequencies using time-trend analysis. It also examines the effects of the IE frequencies obtained from this study on risk insights by applying them to recently updated internal events Level 1 PSA models (at-power and shutdown) for an OPR-1000 plant. As a result, at-power core damage frequency decreased while shutdown core damage frequency increased, with the related contributions from each IE category changing accordingly. These results imply that the incorporation of time-trend analysis leads to different IE frequencies and resulting risk insights. The IE frequency distributions presented in this study can be used in future PSA updates for Korean NPPs, and should be further updated themselves by adding more recent data.

Development of automatic backup systems for turbine speed signal (터빈 속도신호의 자동백업 시스템 개발)

  • Kim, Kwan-Haeng;Kim, Ho-Chan
    • Proceedings of the KIEE Conference
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    • 1999.07b
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    • pp.844-846
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    • 1999
  • A speed signal of governor, which control the output and speed of a generator, is important because a signal failure can be causing the shutdown of a power plant. thus, it is necessary to introduce switching method with two complementary signal. This paper presents a comparative study of speed signal switching methods. One of the Proposed methods has been tested at a power plant in Pukcheju and the approach described here is expected to be of wide applicability.

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Effect of Number of Shutdown on the Decrease of Performance in PEM Water Electrolysis (PEM 수전해에서 정지횟수가 성능 감소에 미치는 영향)

  • Cheunho Chu;Jongwon Yang;Ilchai Na;Yoonjin Park
    • Korean Chemical Engineering Research
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    • v.61 no.2
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    • pp.202-207
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    • 2023
  • In the case of driving water electrolysis by receiving surplus electricity from solar and wind power generation, operation and stopping must be repeated according to weather fluctuations. When the PEMWE(Polymer Electrolyte Membrane Water Electrolysis) is driven and stopped, the PEM fuel cell is in the same state as the PEM fuel cell due to the residual hydrogen and oxygen, and the high potential of the water electrolysis formed during operation is highly likely to cause degradation of the electrode and membrane even during stopping. In this study, in order to check how much degradation of the electrode and membrane progresses during the repeated driving/shutdown process of PEM water electrolysis, the performance decrease was measured by changing the number of driving/shutdown for 144 hours. Changes in electrode catalyst active area, hydrogen permeability and fluorine emision rate of membranes were analyzed to measure changes in the properties of electrodes and polymer membranes. Overall, the PEMWE performance decreased as the number of stops increased. When stopped 5 times in 144 hours, the IrOx catalyst activity decreased by more than 30%, and the hydrogen permeability increased by 80%, confirming that both the electrode and the membrane were deteriorated.