• Title/Summary/Keyword: Containment Spray System

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Investigation of a Hydrogen Mitigation System During Large Break Loss-Of-Coolant Accident for a Two-Loop Pressurized Water Reactor

  • Dehjourian, Mehdi;Sayareh, Reza;Rahgoshay, Mohammad;Jahanfarnia, Gholamreza;Shirani, Amir Saied
    • Nuclear Engineering and Technology
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    • v.48 no.5
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    • pp.1174-1183
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    • 2016
  • Hydrogen release during severe accidents poses a serious threat to containment integrity. Mitigating procedures are necessary to prevent global or local explosions, especially in large steel shell containments. The management of hydrogen safety and prevention of over-pressurization could be implemented through a hydrogen reduction system and spray system. During the course of the hypothetical large break loss-of-coolant accident in a nuclear power plant, hydrogen is generated by a reaction between steam and the fuel-cladding inside the reactor pressure vessel and also core concrete interaction after ejection of melt into the cavity. The MELCOR 1.8.6 was used to assess core degradation and containment behavior during the large break loss-of-coolant accident without the actuation of the safety injection system except for accumulators in Beznau nuclear power plant. Also, hydrogen distribution in containment and performance of hydrogen reduction system were investigated.

Systems Engineering approach to Reliability Centered Maintenance of Containment Spray Pump (시스템즈 엔지니어링 기법을 이용한 격납용기 살수펌프의 신뢰기반 정비기법 도입 연구)

  • Ohaga, Eric Owino;Lee, Yong-Kwan;Jung, Jae Cheon
    • Journal of the Korean Society of Systems Engineering
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    • v.9 no.1
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    • pp.65-84
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    • 2013
  • This paper introduces a systems engineering approach to reliability centered maintenance to address some of the weaknesses. Reliability centered maintenance is a systematic, disciplined process that produces an efficient equipment management strategy to reduce the probability of failure [1]. The study identifies the need for RCM, requirements analysis, design for RCM implementation. Value modeling is used to evaluate the value measures of RCM. The system boundary for the study has been selected as containment spray pump and its motor drive. Failure Mode and Criticality Effects analysis is applied to evaluate the failure modes while the logic tree diagram used to determine the optimum maintenance strategy. It is concluded that condition based maintenance tasks should be enhanced to reduce component degradation and thus improve reliability and availability of the component. It is recommended to apply time directed tasks to age related failures and failure finding tasks to hidden failures.

A Study on the Multiple Spurious Operation Analysis in Fire Events Probabilistic Safety Assessment of Domestic Nuclear Power Plant (국내 원자력발전소의 화재사건 확률론적안전성평가에서 다중오동작 분석 연구)

  • Kang, Dae Il;Jung, Yong Hun;Choi, Sun Yeong;Hwang, Mee-Jeong
    • Journal of the Korean Society of Safety
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    • v.33 no.6
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    • pp.136-143
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    • 2018
  • In this study, we conducted a pilot study on the multiple spurious operations (MSO) analysis in the fire probabilistic safety assessment (PSA) of domestic nuclear power plant (NPP) to identify the degree of influence of the operator actions used in the MSO mitigation strategies. The MSO scenario of the domestic reference NPP selected for this study is refueling water tank (RWT) drain down event. It could be caused by spurious operations of the containment spray system (CSS) of the reference NPP. The RWT drain down event can be stopped by the main control room (MCR) operator actions for stopping the operation of CSS pump or closing the CSS motor operated valve if the containment spray actuation signal (CSAS) is spuriously actuated. Outside the MCR, it can be stopped by operator actions for closing the CSS manual valves or motor operated valve or stopping the operation of CSS pump. The quantification result of a fire PSA model that takes into account all recovery actions for the RWT drain down event lead to risk reduction by about 95%, compared with quantification result of fire PSA model without considering them. Among the various operator actions, the recovery action for the spurious CSAS operations and the operator action for the manual valve are identified as the most important operator actions. This study quantitatively showed the extent to which the operator actions used as MSO countermeasures have affected the fire PSA quantification results. In addition, we can see the rank of importance among the operator recovery actions in quantitative terms.

Analysis of EQ pH Condition and Fission Product Removal Capability for Nuclear Power Plant (원전의 내환경기기검증 화학환경 및 핵분열생성물 제거능력 평가)

  • Song, Dong Soo;Ha, Sang Jun;Seong, Je Joong;Jeon, Hwang Yong;Huh, Seong Cheol
    • Journal of Energy Engineering
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    • v.23 no.3
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    • pp.186-190
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    • 2014
  • Nuclear Power Plants require the control ability of chemical condition (pH) because pH control during transient accident such as LOCA makes an able the fission product removal capability to be maintained, stress corrosion cracking of stainless steel equipment to be prevented and the production of hydrogen by aluminum and zinc to be minimized. An NPP is designed to control the pH of containment spray and sump coolant using the spray additives 30% NaOH in the event of loss of coolant accident. In this paper, the pH of sump coolant of an NPP during LOCA was analyzed and the fission products removal constant and decontamination factor were calculated according to Standard Review Plan 6.5.2 related to spray chemical conditions of pH. The calculated pH value of recirculation mode using the computer code corresponds to 8.09~9.67, which meets the chemical environment regulation requirements. The fission product removal capability caused by containment spray system is performed to provide input to radiation analysis.

The Evaluation of Accident Management Strategy Involving Operator Action

  • Kim, Jaewhan;Jaejoo Ha
    • Nuclear Engineering and Technology
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    • v.29 no.5
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    • pp.368-374
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    • 1997
  • This paper presents a new approach to the evaluation of an accident management strategy when an operator action is involved. This approach classifies the failure in implementing a given strategy into 4 possible mechanisms, and provides their corresponding quantification methods : 1) the failure to formulate correct intention by operators, 2) the failure to take an adequate action following a correct diagnosis, 3) the failure of a system operation following an adequate action, and 4) the failure due to a delayed action. The proposed method was applied to assess a cavity flooding strategy that uses containment spray system (CSS), and the result shows that the method is more appropriate in evaluating accident management strategies when human action is involved.

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Safety-Related Equipment Classification for Maintenance Purposes with Risk Measures

  • Park, Byoung-Chul;Kwon, Jong-Jooh;Cho, Sung-Hwan
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.838-843
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    • 1998
  • Risk importance measures are widely wed to rank risk contributors in risk-based applications. Typically, Fussell-Vesely (F-V) importance and risk achievement worth (RAW) are used in the component importance raking for the reliability centered maintenance (RCM) analysis of safety system in nuclear power plants (NPPs). This study was performed as part of feasibility study on RCM for domestic NPPs, which is focused on the component importance ranking approach the maintenance recommendation. The approach of modulizing faulting tree basic events was applied in the simplification process of the PSA model and the validity of the approach was evaluated As a result of the case study, this paper included the importance and the maintenance recommendations for the safety-related equipments associated with safety injection and containment spray in large loss of coolant accident sequences.

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Application of Fe-Mn High Damping Alloys for Reduction of Noise and Vibration in Power Plants (Fe-Mn 방진합금을 적용한 발전소 격납용기 살수펌프의 소음$\cdot$진동 저감효과에 관한 연구)

  • 백승한
    • Journal of KSNVE
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    • v.9 no.4
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    • pp.720-729
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    • 1999
  • Coventional methods for reducing vibration in engineering designs (i.e. by stifferning or detuning) may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Some alloys with a combination of high damping capacity and good mechanical properties can provide attractive techanical and economical solutions to problems involving seismic, shock and vibration isolation. Although several non ferrous damping alloys have been developed, none of those materials are applied in any industrial factor due largely to high production cost. To meet these requirement, we have developed a new Fe-Mn high damping alloy. In previous studies, we have reported that an Fe-17%Mn alloy exhibits the highest damping capacity(Specific Damping Capacity:SDC, 30%) among Fe-Mn binary system, and proposed that the boundaries of various types such as $\varepsilon$-martensite variant boundaries, stacking faults in $\varepsilon$-martensite, stacking faults in austenitic and ${\gamma}$$\gamma /\varepsilon$ interfaces give rise to a high damping capacity. The Fe-17%Mn alloy also has advantages of good mechanical properties(T.S. 70 kg/nm$^2$ and low cost over other damping alloys(1/4 times the cost of non-ferrous damping alloy). Thus, the Fe-17%Mn high damping alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components. In this paper, the overall properties of the Fe-17%Mn high damping alloy is introduced, and its applicability to containment spray pump in the power plant is discussed.

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