• Nuclear Engineering and Technology
• /
• 제56권5호
• /
• pp.1698-1711
• /
• 2024

Heat pipe cooled reactors have gained attention as a potential solution for nuclear power generation in space and deep sea applications because of their simple design, scalability, safety and reliability. However, under complex operating conditions, a control strategy for variable load operation is necessary. This paper presents a two-dimensional transient characteristics analysis program for a heat pipe cooled reactor and proposes a variable load control strategy using the recuperator bypass (CSURB). The program was verified against previous studies, and steady-state and step-load operating conditions were calculated. For normal operating condition, the predicted temperature distribution with constant heat pipe temperature boundary conditions agrees well with the literature, with a maximum temperature difference of 0.4 K. With the implementation of the control strategy using the recuperator bypass (CSURB) proposed in this paper, it becomes feasible to achieve variable load operation and return the system to a steady state solely through the self-regulation of the reactor, without the need to operate the control drum. The average temperature difference of the fuel does not exceed 1 % at the four power levels of 70 %,80 %, 90 % and 100 % Full power. The output power of the turbine can match the load change process, and the temperature difference between the inlet and outlet of the turbine increases as the power decreases.

• 대한조선학회논문집
• /
• 제34권4호
• /
• pp.127-138
• /
• 1997

본 연구에서는 선박의 기본설계 단계에서 정의된 선도를 입력 정보로 하여 순정도 높은 선형을 표현할 수 있는 기법을 개발하였다. 곡선모델링의 경우, de Casteljau (드 카스텔죠)알고리듬과 Bezier 조정점을 이용하여 자유곡선을 표현하였고, 이를 토대로 Non-Uniform B-Spline(NUB) 곡선, Spline곡선 등으로 서로 변환(Conversion)할 수 있는 Unified curve modeling( 곡선모델링 단일화) 기법을 정립하였다. 곡면모델링의 경우, 곡면정의를 위하여 입력되는 그물망 곡선(Mesh curve net)을 먼저 Unified curve modeling 기법에 의하여 Interpolation(보간)한 후, "Remeshing" (그물망 곡선의 재생성)기법에 의하여 Gregory surface patch(그레고리 곡면 patch)의 Mesh curve segment(경계 세그멘트 곡선)를 생성하고 이를 접속하여 순정도 높은 Composite surface(합성곡면)를 만드는 기법을 개발하였다.

• Nuclear Engineering and Technology
• /
• 제53권3호
• /
• pp.732-740
• /
• 2021

Scattering resonance of medium mass nuclides leads complex spectrum in the fast reactor, which requires thousands of energy groups in the spectrum calculation. When the broad-group cross sections are collapsed, reaction rate cannot be completely conserved. To eliminate the error from energy collapsing, the Super-homogenization method in energy collapsing (ESPH) was employed in the fast reactor code SARAX. An ESPH factor was derived based on the ESPH-corrected SN transport equation. By applying the factor in problems with reflective boundary condition, both the effective multiplication factor and reaction rate were conserved. The fixed-source iteration was used to ensure the stability of ESPH iteration. However, in the energy collapsing process of SARAX, the vacuum boundary condition was adopted, which was necessary for fast reactors with strong heterogeneity. To further reduce the error caused by leakage, an additional conservation factor was proposed to correct the neutron current in energy collapsing. To evaluate the performance of ESPH with conservation factor, numerical benchmarks of fast reactors were calculated. The results of broad-group calculation agreed well with the direct full-core Monte-Carlo calculation, including the effective multiplication factor, radial power distribution, total control rod worth and sodium void worth.

• 한국전산응용수학회:학술대회논문집
• /
• 한국전산응용수학회 2003년도 KSCAM 학술발표회 프로그램 및 초록집
• /
• pp.6-6
• /
• 2003

In this work we consider the mathematical formulation and numerical resolution of the linear feedback control problem for Boussinesq equations. The controlled Boussinesq equations is given by $$\frac{{\partial}u}{{\partial}t}-{\nu}{\Delta}u+(u{\cdot}{\nabla}u+{\nabla}p={\beta}{\theta}g+f+F\;\;in\;(0,\;T){\times}\;{\Omega}$$, $${\nabla}{\cdot}u=0\;\;in\;(0,\;T){\times}{\Omega}$$, $$u|_{{\partial}{\Omega}=0,\;u(0,x)=\;u_0(x)$$ $$\frac{{\partial}{\theta}}{{\partial}t}-k{\Delta}{\theta}+(u{\cdot}){\theta}={\tau}+T,\;\;in(0,\;T){\times}{\Omega}$$ $${\theta}|_{{\partial}{\Omega}=0,\;\;{\theta}(0,X)={\theta}_0(X)$$, where $\Omega$ is a bounded open set in $R^{n}$, n=2 or 3 with a $C^{\infty}$ boundary ${\partial}{\Omega}$. The control is achieved by means of a linear feedback law relating the body forces to the velocity and temperature field, i.e., $$f=-{\gamma}_1(u-U),\;\;{\tau}=-{\gamma}_2({\theta}-{\Theta}}$$ where (U,$\Theta$) are target velocity and temperature. We show that the unsteady solutions to Boussinesq equations are stabilizable by internal controllers with exponential decaying property. In order to compute (approximations to) solution, semi discrete-in-time and full space-time discrete approximations are also studied. We prove that the difference between the solution of the discrete problem and the target solution decay to zero exponentially for sufficiently small time step.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 추계학술발표회논문집(1)
• /
• pp.191-196
• /
• 1996

The potential value of the Application Specific Integrated Circuits(ASIC's) in safety systems of Nuclear Power Plants(NPP's) is being increasingly recognized because they are essentially hardwired circuitry on a chip, the reliability of the system can be proved more easily than that of software based systems which is difficult in point of software V&V(Verification and Validation). There are two types of ASIC, one is a full customized type, the other is a half customized type. PLD(Programmable Logic Device) used in this paper is a half customized ASIC which is a device consisting of blocks of logic connected with programmable interconnections that are customized in the package by end users. This paper describes the RPS(Reactor Protection System) composed of ASICs which provides emergency shutdown of the reactor to protect the core and the pressure boundary of RCS(Reactor Coolant System) in NPP's. The RPS is largely composed of five logic blocks, each of them was implemented in one PLD, as the followings. A). Bistable Logic B). Matrix Logic C).Initiation Logic D). MMI(Man Machine Interface) Logic E). Test Logic.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1778-1783
• /
• 2000

When visual intrusion is an important factor, it is desirable to find alternative methods of improving the insertion loss of a noise barrier without increasing the height. Therefore, the primary object of the work attenuates the noise due to transport vehicle by small interference device installed at noise barrier edge. In this paper the performance of noise barriers with attached interference device, in terms of shape, absorptive material and split panel, are examined using the boundary element approach. Also, the scale models are moanted in an anechoic chamber and the frequency of the sound sources are appropriately scaled to simulate full scale site conditions. Lastly, experimental measurements of the designs are executed for a range of frequencies and receiver positions, and are compared with the results of numerical modeling.

• 한국자동차공학회논문집
• /
• 제8권5호
• /
• pp.114-120
• /
• 2000

Friction forces of piston rings for a typical SI engine were independently measured while excluding the effects of cylinder pressure, oil starvation and piston secondary motion using a floating liner system. Friction patterns, represented by the measured friction forces, were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(mid-stroke and dead centers). The modes were identified on the Stribeck diagram of the dimensionless bearing parameter and friction coefficients which were evaluated at the mid-stroke and at the dead centers. And the frictional modes were estimated to the full operation range. The compression rings behave in the mode where hydrodynamic lubrication is dominant at the mid-stroke and mixed lubrication is dominant at the dead centers under steady operating conditions. However, the oil control ring behave in the mode where mixed lubrication is dominant throughout the entire stroke.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
• /
• pp.152-155
• /
• 2009

In high power application, PFC(Power Factor Correction) pre-regulators are generally required. PFC pre-regulators could achieve unity power factor, reduce line input current harmonics and utilize full line power. Interleaving PFC converters could reduce input ripple current, output capacitor ripple current and inductor size. With this closed loop interleaving method, both two phase converters are working at the boundary between continuous and discontinuous mode and accurate 180 degree phase shift is achieved. Implementation of this strategy could be easily integrated to the control chip. Finally, experimental results of a two-phase interleaved boost PFC are presented to verify the discussed features.

• Structural Engineering and Mechanics
• /
• 제70권6호
• /
• pp.765-779
• /
• 2019

Most of the existing evaluation criteria of vibration serviceability rely on the peak acceleration of the structure rather than that of the people keeping their own body unmoved on the structure who is the real receiver of structural vibrations. In order to accurately assess the vibration serviceability, therefore, a full path assessment approach of vibration serviceability based on vibration source, path and receiver is not only tentatively proposed in this paper, taking the peak acceleration of receiver into account, but also introduce a probability procedure to provide more instructive information instead of a single value. In fact, semi-rigid supported on both sides of the structure is more consistent with the actual situation than simply supported or clamped due to the application of the prefabricated footbridge structures. So, the footbridge is regarded as a beam with semi-rigid supported on both sides in this paper. The differential quadrature-integral quadrature coupled method is not only to handle different type of boundary conditions, but also after being further modified via the introduction of an approximation procedure in this work, the time-varying system problem caused by human-structure interaction can be solved well. The analytical results of numerical simulations demonstrate that the modified differential quadrature-integral quadrature coupled method has higher reliability and accuracy compared with the mode superposition method. What's more, both of the two different passive control measures, the tuned mass damper and semi-rigid supported, have good performance for reducing vibrations. Most importantly, semi-rigid supported is easier to achieve the objective of reducing vibration compared with tuned mass damper in design stage of structure.

• 전력전자학회논문지
• /
• 제4권1호
• /
• pp.13-18
• /
• 1999

본 논문은 공간전압벡터 PMW 인버터에서 전압벡터로 구성된 육각형 내부의 전압영역을 충분히 이용함으로써 보다 많은 출력 전압을 얻을 수 있도록 하는 새로운 과변조 기법을 제안한다. 제안된 과변조 기법은 벡터제어에 적용할 수 있어, 높은 전압이 요구 되는 운전 영역에서 벡터제어 전동기 구동시스템의 출력 토크능력을 향상시킬수 있다. 제안된 기법에서는 벡터 제어시 요구되는 특성인 자속의 제어\ulcorner역을 과변조 운전영역에서도 유지하도록 자속성분 전류를 우선적으로 제어하고, 그 대신 토크 성분 전류는 약간 희생하도록 하여, 과변조 운전영역에서도 벡터제어가 잘 수행되도록 하였다. 이를 위해, 과변조시 자속을 제어하는 전류제어기의 d축 출력전압은 제안없이 보존하는 반면, 토크를 제어하는 전류제어기의 q축 출력전압은 지령 전압벡터가 육각형 변위에 위치하도록 제한한다. 22[kW] 유도전동기 구동시스템에 대한 시뮬레이션 및 실험을 통해 제안된 기법의 타당성을 검증하였다.