• Title/Summary/Keyword: Vessel design

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A Study on the Supporting Location Optimization a Structure Under Non-Uniform Load Using Genetic Algorithm (유전알고리듬을 이용한 비균일 하중을 받는 구조물의 지지위치 최적화 연구)

  • Lee Young-Shin;Bak Joo-Shik;Kim Geun-Hong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1558-1565
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    • 2004
  • It is important to determine supporting locations for structural stability when a structure is loaded with non-uniform load or supporting locations as well as the number of the supporting structures are restricted by the problem of space. Moreover, the supporting location optimization of complex structure in real world is frequently faced with discontinuous design space. Therefore, the traditional optimization methods based on derivative are not suitable Whereas, Genetic Algorithm (CA) based on stochastic search technique is a very robust and general method. The KSTAR in-vessel control coil installed in vacuum vessel is loaded with non- uniform electro-magnetic load and supporting locations are restricted by the problem of space. This paper shows the supporting location optimization for structural stability of the in-vessel control coil. Optimization has been performed by means of a developed program. It consists of a Finite Element Analysis interfaced with a Genetic Algorithm. In addition, this paper presents an algorithm to find an optimum solution in discontinuous space using continuous design variables.

Asymmetric Thermal-Mixing Analysis due to Partial Loop Stagnation during Design Basis Accident of NPP (원전 설계기준 사고시 냉각재계통 부분정체로 인한 비대칭 열유동 혼합해석에 관한 연구)

  • Hwang, K.M.;Jin, T.E.;Kim, K.H.
    • Journal of ILASS-Korea
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    • v.8 no.1
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    • pp.23-28
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    • 2003
  • When a cold HPSI (High Pressure Safety Injection) fluid associated with a design basis accident, such as LOCA (Loss of Coolant Accident), enters the cold legs of a stagnated primary coolant loop, thermal stratification phenomena may arise due to incomplete mixing. If the stratified flow enters a reactor pressure vessel downcomer, severe thermal stresses are created in a radiation embrittled vessel wall by local overcooling. Previous thermal-mixing analyses have assumed that the thermal stratification phenomena generated in stagnated loop of a partially stagnated collant loop are neutralized in the vessel downcomer by strong flow from unstagnated loop. On the basis of these reasons, this paper presents the thermal-mixing analysis results in order to identify the fact that the cold plume generated in the vessel downcomer due to the thermal stratification phenomena of the stagnated loop is affected by the strong flow of the unstagnated loop.

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Thermal Stress at the Junction of Skirt to Head in Hot Pressure Vessel (고온 수직형 압력용기 Skirt 부의 열응력에 관한 연구)

  • 한명수;한종만;조용관
    • Journal of Welding and Joining
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    • v.16 no.2
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    • pp.111-121
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    • 1998
  • It is well recognized that a excessive temperature gradient from the junction of head to skirt in axial direction in a hot pressure vessel can cause unpredicted high thermal stress at the junction and/or in axial direction of a skirt. this thermal stress resulting from axial thermal gradient may be a major cause of unsoundness of structural integrity. In case of cyclic operation of hot pressure vessels, the thermal stress becomes one of the primary design consideration because of the possibility of fracture as a result of cyclic thermal fatigue and progressively incremental plastic deformation. To perform thermal stress analysis of the junction and cylindrical skirt of a vessel, or, at least, to inspect quantitatively the magnitude and effect of thermal stress, the temperature profile of the vessel and skirt must be known. This paper demonstrated the temperature distribution and thermal stress analysis for the junction of skirt to head using F.E. analysis. Effect of air pocket in crotch space was quantitatively investigated to minimize the temperature gradient causing the thermal stress in axial direction. Effect of the skirt height on thermal stresses was also studied. Analysis results were compared with theoretical formulas to verify th applicability to the strength calculation in design field.

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PWM-Based Sliding Mode Controller for Three-Level Full-Bridge DC-DC Converter that Eliminates Static Output Voltage Error

  • Liu, Jilong;Xiao, Fei;Ma, Weiming;Fan, Xuexin;Chen, Wei
    • Journal of Power Electronics
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    • v.15 no.2
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    • pp.378-388
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    • 2015
  • This paper proposes a pulse width modulation (PWM)-based sliding mode controller (SMC) for a full-bridge DC-DC converter that can eliminate static output voltage error. Hysteretic SMC in DC-DC converter does not have a fixed switching frequency, and applying hysteretic SMC to full-bridge converters is difficult. Fixed-frequency SMC, which is also called PWM-based SMC, based on equivalent control overcomes these shortcomings. However, the controller order reduction in equivalent control in PWM-based SMC causes static output voltage error. To resolve this issue, an integral item is added to the PWM-based SMC. Sliding mode coefficients are designed by applying a standard second-order system to the sliding mode surface. The effect of adding an integral item on the controller is analyzed, and an integral coefficient design method is proposed. Experiment results on a three-level full-bridge DC-DC converter verify the control scheme and design method proposed in this paper.

Analysis of the flow distribution and mixing characteristics in the reactor pressure vessel

  • Tong, L.L.;Hou, L.Q.;Cao, X.W.
    • Nuclear Engineering and Technology
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    • v.53 no.1
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    • pp.93-102
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    • 2021
  • The analysis of the fluid flow characteristics in reactor pressure vessel is an important part of the hydraulic design of nuclear power plant, which is related to the structure design of reactor internals, the flow distribution at core inlet and the safety of nuclear power plant. The flow distribution and mixing characteristics in the pressurized reactor vessel for the 1000MWe advanced pressurized water reactor is analyzed by using Computational Fluid Dynamics (CFD) method in this study. The geometry model of the full-scaled reactor vessel is built, which includes the cold and hot legs, downcomer, lower plenum, core, upper plenum, top plenum, and is verified with some parameters in DCD. Under normal condition, it is found that the flow skirt, core plate holes and outlet pipe cause pressure loss. The maximum and minimum flow coefficient is 1.028 and 0.961 respectively, and the standard deviation is 0.019. Compared with other reactor type, it shows relatively uniform of the flow distribution at the core inlet. The coolant mixing coefficient is investigated with adding additional variables, showing that mass transfer of coolant occurs near the interface. The coolant mainly distributes in the 90° area of the corresponding core inlet, and mixes at the interface with the coolant from the adjacent cold leg. 0.1% of corresponding coolant is still distributed at the inlet of the outer-ring components, indicating wide range of mixing coefficient distribution.

GA-LADRC based control for course keeping applied to a mariner class vessel (GA-LADRC를 이용한 Mariner class vessel의 선수각 제어)

  • Jong-Kap AHN
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.59 no.2
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    • pp.145-154
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    • 2023
  • In this study, to control the heading angle of a ship, which is constantly subjected to various internal and external disturbances during the voyage, an LADRC (linear active disturbance rejection control) design that focuses more on improving the disturbance removal performance was proposed. The speed rate of change of the ship's heading angle due to the turn of the rudder angle was selected as a significant factor, and the nonlinear model of the ship's maneuvering equation, including the steering gear, was treated as a total disturbance. It is the similar process with an LADRC design for the first-order transfer function model. At this time, the gains of the controller included in LADRC and the gains of the extended state observer were tuned to RCGAs (real-coded genetic algorithms) to minimize the integral time-weighted absolute error as an evaluation function. The simulation was performed by applying the proposed GA-LADRC controller to the heading angle control of the Mariner class vessel. In particular, it was confirmed that the proposed controller satisfactorily maintains and follows the set course even when the disturbances such as nonlinearity, modelling error, uncertainty and noise of the measurement sensor are considered.

Application of two different similarity laws for the RVACS design

  • Min Ho Lee;Ji Hwan Hwang;Ki Hyun Choi;Dong Wook Jerng;In Cheol Bang
    • Nuclear Engineering and Technology
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    • v.54 no.12
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    • pp.4759-4775
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    • 2022
  • The RVACS is a versatile and robust safety system driven by two natural circulations: in-vessel coolant and ex-vessel air. To observe interaction between the two natural circulations, SINCRO-IT facility was designed with two different similarity laws simultaneously. Bo' based similarity law was employed for the in-vessel, while Ishii's similarity law for the ex-vessel excluding the radiation. Compared to the prototype, the sodium and air system, SINCRO-IT was designed with Wood's metal and air, having 1:4 of the length reduction, and 1.68:1 of the time scale ratio. For the steady state, RV temperature limit was violated at 0.8% of the decay heat, while the sodium boiling was predicted at 1.3%. It showed good accordance with the system code, TRACE. For an arbitrary re-criticality scenario with RVACS solitary operation, sodium boiling was predicted at 25,100 s after power increase from 1.0 to 2.0%, while the system code showed 30,300. Maximum temperature discrepancy between the experiments and system code was 4.2%. The design and methodology were validated by the system code TRACE in terms of the convection, and simultaneously, the system code was validated against the simulating experiments SINCRO-IT. The validated RVACS model could be imported to further accident analysis.

A Study on the Basic Design for Platform Support Vessel (PSV) and Hull Form Development for Enhancement of Resistance & Propulsion Performance (해양작업지원선(PSV)의 기본설계 및 저항추진 성능 향상을 위한 선형개선 방안 연구)

  • Yum, Jong-Gil;Kang, Kuk-Jin;Lee, Young-Yeon;Lee, Chun-Ju;Ok, Kun-Do
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.3
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    • pp.196-204
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    • 2018
  • Present paper shows the basic design procedure for platform support vessel operating in open sea, and hull form development process. General design concept considering the operating mission, operating sea condition and shipping freight, etc. is explained shortly. For the hull form design, the initial hull form was designed based on the reference PSVs. The resistance and propulsion test results for the initial hull form with twin Azimuth thruster were analyzed and a few items for improvement were derived. At the next stage, main parameters including Length, Cp-curve, Cb, Lcb, etc. were changed totally for the hull form improvement. Furthermore, 3 different bulbous bows for the fore-body design to reduce the wave resistance and after-body design to reduce the residual resistance were carried out. The best hull form among the 3 fore-bodies with same after-body was selected through the comparison of wave resistance calculation results. Twin ducted Azimuth thruster with the smaller propeller diameter than the former were adapted to increase the propulsive efficiency. The final hull form with the twin Azimuth thruster was evaluated to satisfy more than the target design speed 14 knots in sea condition with sea margin 15% at the 5,000kW BHP through the model test in KRISO.

Development of Reactor Vessel Head Penetration Performance Demonstration System in Korea (국내 원자로 상부헤드관통관 기량검증 기술개발)

  • Kim, Yongsik;Yoon, Byungsik;Yang, Seunghan
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.10 no.1
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    • pp.44-50
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    • 2014
  • There were many flaw issues of reactor vessel head penetration in USA fleets. USNRC issued 10CFR50.55a to implement reactor vessel head penetration ultrasonic examination performance demonstration(PD) in US for enhancement of inspection reliability. After September 2009, all US utilities inspected their RVHP with PD qualified system. Korea Hydro and Nuclear Power Company(KHNP) have developed reactor vessel head penetration performance demonstration system for ultrasonic test to apply for pressurized light-water reactor power plants in accordance with 10CFR50.55a since September 2011. RVHP configuration surveying and analysis, code requirement analysis, and performance demonstration specimen design were performed up to this day. Fingerprinting of manufactured specimen, development of test data management program, development of operation procedure, input of flawed data, and development of final report will be performed for the next step. This paper describes the development status of the performance demonstration system for reactor vessel head penetration ultrasonic examination in Korea.

Neutron Fluence Evaluation for Reactor Pressure Vessel Using 3D Discrete Ordinates Transport Code RAPTOR-M3G (3차원 수송계산 코드(RAPTOR-M3G)를 이용한 원자로 압력용기 중성자 조사량 평가)

  • Maeng, Young Jae;Lim, Mi Joung;Kim, Byoung Chul
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.10 no.1
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    • pp.107-112
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    • 2014
  • The Code of Federal Regulations, Title 10, Part 50, Appendix H requires surveillance program for reactor pressure vessel(RPV) that the peak neutron fluence at the end of the design life of the vessel will exceed $1.0E+17n/cm^2$ (E>1.0MeV). 2D/1D Synthesis method based on DORT 3.1 transport calculation code has been widely used to determine fast neutron(E>1.0MeV) fluence exposure to RPV in the beltline region. RAPTOR-M3G(RApid Parallel Transport Of Radiation-Multiple 3D Geometries) performing full 3D transport calculation was developed by Westinghouse and KRIST(Korea Reactor Integrity Surveillance Technology) and applied for the evaluations of In-Vessel and Ex-Vessel neutron dosimetry. The reaction rates from measurement and calculation were compared and the results show good agreements each other.