• Title/Summary/Keyword: Damping Reactor

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INTEGRITY ANALYSIS OF AN UPPER GUIDE STRUCTURE FLANGE

  • LEE, KI-HYOUNG;KANG, SUNG-SIK;JHUNG, MYUNG JO
    • Nuclear Engineering and Technology
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    • v.47 no.6
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    • pp.766-775
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    • 2015
  • The integrity assessment of reactor vessel internals should be conducted in the design process to secure the safety of nuclear power plants. Various loads such as self-weight, seismic load, flow-induced load, and preload are applied to the internals. Therefore, the American Society of Mechanical Engineers (ASME) Code, Section III, defines the stress limit for reactor vessel internals. The present study focused on structural response analyses of the upper guide structure upper flange. The distributions of the stress intensity in the flange body were analyzed under various design load cases during normal operation. The allowable stress intensities along the expected sections of stress concentration were derived from the results of the finite element analysis for evaluating the structural integrity of the flange design. Furthermore, seismic analyses of the upper flange were performed to identify dynamic behavior with respect to the seismic and impact input. The mode superposition and full transient methods were used to perform time-history analyses, and the displacement at the lower end of the flange was obtained. The effect of the damping ratio on the response of the flange was also evaluated, and the acceleration was obtained. The results of elastic and seismic analyses in this study will be used as basic information to judge whether a flange design meets the acceptance criteria.

Development of Guidelines for seismic isolation Design of LMR (액체금속로 면진설계를 위한 지침서 개발)

  • Yoo, Bong;Koo, Gyeong-Hoi;Lee, Jae-Han
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.04a
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    • pp.147-154
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    • 1998
  • The purpose of this paper is to propose the draft guidelines of seismic isolation design of Liquid Metal Reactor (LMR) using high damping laminated rubber bearings. The scopes of guidelines include design requirements of a seismically isolated system and components, seismic isolator, isolation system, interface system between seismic isolation and non-seismic isolation part, qualification and acceptance tests of seismic isolator, seismic isolation reliability, and seismic safety and monitoring system. Proposed guidelines shall be revised to extend to general design guideline for nuclear facilities by further research and discussions.

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Analysis of activated colloidal crud in advanced and modular reactor under pump coastdown with kinetic corrosion

  • Khurram Mehboob;Yahya A. Al-Zahrani
    • Nuclear Engineering and Technology
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    • v.54 no.12
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    • pp.4571-4584
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    • 2022
  • The analysis of rapid flow transients in Reactor Coolant Pumps (RCP) is essential for a reactor safety study. An accurate and precise analysis of the RCP coastdown is necessary for the reactor design. The coastdown of RCP affects the coolant temperature and the colloidal crud in the primary coolant. A realistic and kinetic model has been used to investigate the behavior of activated colloidal crud in the primary coolant and steam generator that solves the pump speed analytically. The analytic solution of the non-dimensional flow rate has been determined by the energy ratio β. The kinetic energy of the coolant fluid and the kinetic energy stored in the rotating parts of a pump are two essential parameters in the form of β. Under normal operation, the pump's speed and moment of inertia are constant. However, in a coastdown situation, kinetic damping in the interval has been implemented. A dynamic model ACCP-SMART has been developed for System Integrated Modular and Advanced Reactor (SMART) to investigate the corrosion due to activated colloidal crud. The Fickian diffusion model has been implemented as the reference corrosion model for the constituent component of the primary loop of the SMART reactor. The activated colloidal crud activity in the primary coolant and steam generator of the SMART reactor has been studied for different equilibrium corrosion rates, linear increase in corrosion rate, and dynamic RCP coastdown situation energy ratio b. The coolant specific activity of SMART reactor equilibrium corrosion (4.0 mg s-1) has been found 9.63×10-3 µCi cm-3, 3.53×10-3 µC cm-3, 2.39×10-2 µC cm-3, 8.10×10-3 µC cm-3, 6.77× 10-3 µC cm-3, 4.95×10-4 µC cm-3, 1.19×10-3 µC cm-3, and 7.87×10-4 µC cm-3 for 24Na, 54Mn, 56Mn, 59Fe, 58Co, 60Co, 99Mo, and 51Cr which are 14.95%, 5.48%, 37.08%, 12.57%, 10.51%, 0.77%, 18.50%, and 0.12% respectively. For linear and exponential coastdown with a constant corrosion rate, the total coolant and steam generator activity approaches a higher saturation value than the normal values. The coolant and steam generator activity changes considerably with kinetic corrosion rate, equilibrium corrosion, growth of corrosion rate (ΔC/Δt), and RCP coastdown situations. The effect of the RCP coastdown on the specific activity of the steam generators is smeared by linearly rising corrosion rates, equilibrium corrosion, and rapid coasting down of the RCP. However, the time taken to reach the saturation activity is also influenced by the slope of corrosion rate, coastdown situation, equilibrium corrosion rate, and energy ratio β.

Seismic Response of Seismically-Isolated Nuclear Power Plants considering Age-related Degradation of High Damping Rubber Bearing (고감쇠고무 적층받침의 경년열화를 고려한 원전구조물의 지진응답)

  • Park, Junhee;Choun, Young-Sun;Choi, In-Kil
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.2
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    • pp.131-138
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    • 2013
  • The high damping rubber bearings contributed to reduce a seismic force transmitted to upper structures, the material properties of rubber changes with time and the rubber with age-related degradation can affect the seismic response of structures and equipments. Therefore the seismic response of structure considering age-related degradation of isolators should be evaluated. In this paper, the stiffness and damping for isolators were defined using the aging data proposed by other researchers. The reactor containment building and the auxiliary building were selected to conduct the nonlinear analysis and the natural frequency, maximum responses, floor response spectrum(FRS) were evaluated with time using the four earthquakes with different frequency contents. According to the analysis results, the seismic responses are increased by the age-related degradation of isolators and the detail inspections should be conducted up to 20 years because it was presented that the change of FRS was high during this period.

Finite Element Analysis for Evaluation of Viscous and Eccentricity Effects on Fluid Added Mass and Damping (유체 부가질량 및 감쇠 결정시 점성 및 편심 영향에 대한 유한요소해석)

  • 구경회;이재한
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.2
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    • pp.21-27
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    • 2003
  • In general, simple fluid added mass method is used for the seismic and vibration analysis of the immersed structure to consider the fluid-structure interaction effect. Actually, the structural response of the immersed structure can be affected by both the fluid added mass and damping caused by the fluid viscosity. These variables appeared as a consistent matrix form with the coupling terms. In this paper, finite element formula for the inviscid fluid case and viscous fluid case are derived from the linearized Navier Stoke's equations. Using the finite element program developed in this paper, the analyses of fluid added mass and damping for the hexagon core structure of the liquid metal reactor are carried out to investigate the effect of fluid viscosity with variation of the fluid gap and Reynolds number. From the analysis results, it is verified that the viscosity significantly affects the fluid added mass and damping as the fluid gap size decrease. From the analysis results of eccentricity effect on the fluid added mass and damping of the concentric cylinders, the fluid added mass increase as the eccentricity increases, however the fluid damping increases only when the eccentricity is very severe.

An Experimental Study on PWR Nuclear Fuel Assembly Vibration (경수로 핵연료집합체 진동의 실험적 고찰)

  • 장영기;김규태;조규종
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.82-87
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    • 2003
  • Nuclear fuel with a big slenderness ratio is susceptible to flow-induced vibration under very severe conditions of high temperature, high flow and exposure to irradiation in nuclear reactor. The fuel assembly should, therefore, be designed to escape any resonance due to the vibration during the reactor operation, in particular, in case of the design changes. In addition, the amplitudes due to the grid vibration, the fuel rod vibration and the fuel assembly vibration should be minimized to reduce the grid-to-rod fretting wear. Fuel assembly vibration tests in air at room temperature and in water at high temperature have been performed to investigate fuel vibration behaviors. The frequency and damping during the test in air have been compared to those in water. Through the hydraulic test, the advanced assembly has been evaluated not to be susceptible to any resonance. In addition, the test data from the tests can be used to make fuel model and to evaluate grid-to-rod fretting wear.

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Optimization for Xenon Oscillation in Load Following Operation of PWR (가압경수형 원자로 부하추종 운전시 제논진동 최적화)

  • 김건중;오성헌;박인용
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.38 no.11
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    • pp.861-869
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    • 1989
  • The optimization problems, based on Pontryagin's Maximum Principle, for minimizing (damping) Xenon spatial oscillations in Load Following operations of Pressurized Water Reactor (PWR) is presented. The optimization model is formulated as an optimal tracking problem with quadratic objective functional. The oen-group diffusion equations and Xe-I dynamic equations are defined as equality constraints. By applying the maximum principle, the original problem is decomposed into a single time problem with no constraints. The resultant subproblems are optimized by using the conjugate Gradient Method. The computational results show that the Xenon spatial oscillation is minimized, and the reactor follows the load demand of the electrical power systems while maintaining the desired power distribution.

Generation of Design Time History Complying With Japanese Seismic Design Standards for Nuclear Power Plants (일본 원전 내진설계 기술기준을 적용한 모의지진파(가속 도시간이력) 작성)

  • Gin, Seungmin;Kim, Yongbog;Lee, Yongsun;Moon, Il Hwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.25 no.2
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    • pp.83-91
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    • 2021
  • Seismic designs for Korean nuclear power plants (NPPs) under earthquakes' design basis are noticed due to the recent earthquake events in Korea and Japan. Japan has developed the technologies and experiences of the NPPs through theoretical research and experimental verification with extensively accumulated measurement data. This paper describes the main features of the design-time history complying with the Japanese seismic design standard. Proper seed motions in the earthquake catalog are used to generate one set of design time histories. A magnitude and epicentral distance specify the amplitude envelope function configuring the shape of the earthquake. Cumulative velocity response spectral values of the design time histories are compared and checked to the target response spectra. Spectral accelerations of the time histories and the multiple-damping target response spectra are also checked to exceed. The generated design time histories are input to the reactor building seismic analyses with fixed-base boundary conditions to calculate the seismic responses. Another set of design time histories is generated to comply with Korean seismic design procedures for NPPs and used for seismic input motions to the same reactor containment building seismic analyses. The responses at the dome apex of the building are compared and analyzed. The generated design time histories will be also applied to subsequent seismic analyses of other Korean standard NPP structures.

Digital Time-Domain Simulation of Ferroresonance of Potential Transformer in the 154 kV GAS Insulated Substation

  • Shim, Eung-Bo;Woo, Jung-Wook;Han, Sang-Ok
    • KIEE International Transactions on Power Engineering
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    • v.11A no.4
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    • pp.9-14
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    • 2001
  • This paper reports a set of digital time-domain simulation studies conducted on 154 kV wound Potential Transformer(PT) int he 154 kV Gas Insulated Substation(GIS). The Electro-Magnetic Transient Program(EMTP) is used to develop the PT model and conduct the transient studies. The accuracy of the PT model is verified through comparison of the EMTP simulation results with those obtained from the field test results. The investigations shows that the developed model can accurately predict PT transient resonance, especially, the phenomenon of ferroresonance. The model is developed not only to determine impact of transients on PT response but also to design ferroresonance suppressor devices of PT. And it can also be used to predict PT transient response on power system monitoring and protection scheme.

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Parametric Study on Earthquake Responses of Soil-structure Interaction System by Substructure Method. (부분구조법에 의한 지반-구조물 상호작용 시스템의 지진응답 매재변수 해석)

  • 조양희
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1997.10a
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    • pp.117-125
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    • 1997
  • ABSTRACT This paper presents results of parametric studies of the seismic responses of a reactor containment structure on layered base soil. Among the numerous parameters, this study concentrates on the effects of embedment of structure to the base soil, thickness of the soil layers, stiffness of the base soil, and the definition point of the input motion. For the analysis, a substructure method using frequency independent impedances is adopted. The method is based on the mode superposition method in time domain using the composite modal damping values of the SSI system computed from the ratio of dissipated energy to the strain energy for each mode. From the study results, the sensitives of each parameter on the earthquake responses have been suggested for the practical application of the substructure method of SSI analysis.

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