• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.167-174
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• 1997

The method that the operating condition of Control Rod Drive Mechanism (CRDM) can be monitored without mounting sensors within CRDM housing was developed, and by using this developed method the closed-loop controller for the CRDM was designed which can optimize the performance and maximize the reliability of CRDM operation. Neural network is utilized as pattern recognition engine in detecting CRDM actuation. In this paper, most problems in previous open loop system are resolved. The control algorithms for closed-loop system ore developed and implemented within the hardware of timing controller based on microprocessor. All functions in the timing controller ore verified by means of real time CRDM simulator. The results show that the timing controller performs its intended functions properly.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1732-1735
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• 2003

In this paper, a DSP-based test apparatus for Control Rod Drive Mechanism (CRDM) that is used in nuclear power plants is described. Using this apparatus, we can test the mechanical and electrical characteristics of CRDM and obtain some information about how to improve the CRDM further and how to design a power controller to actuate the CRDM. Since firing angles can be directly applied to the gate-drive circuits of thyristors in the power controller by using this apparatus, the maximum and minimum values of firing angles within available limits are easily measured. Also step-current inputs help us investigate each coil's response characteristics. Therefore, we can easily find the range of control gains which enables a stable CRDM operation in insertion and withdrawal actions at high speed, mid speed, and low speed. Since this apparatus has a test mode in which an insertion or withdrawal action is divided into several phases so that the current command for each phase is given step by step, we may judge whether the CRDM works as expected or not. We also describe a fault detection capability of the test apparatus for the power controller by using discrete Fourier transform.

• Proceedings of the Korea Society of Design Studies Conference
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• 2004.05a
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• pp.200-201
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• 2004

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.552-558
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• 2016

A control rod drive mechanism(CRDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod within a reactor core to control the reactivity of the core. The CRDM for Jordan Research and Training Reactor with 5MW power has been designed and fabricated based on the HANARO’s experience through KAERI and DAEWOO consortium. This paper describes the seismic test results to demonstrate the operability, the drop performance and the structural integrity of CRDM during or after seismic excitations. The seismic tests are carried out under 5 OBE and 1 SSE loads at three Test Rigs simulating the reactor structure and the pool top. From the tests, the CRDM is smoothly driven without a malfunction of stepping motor under OBE load. The pure drop time under OBE and SSE loads is measured as 1.169s and 1.855s to meet the design requirement. Also, it is found that the CRDM maintains the structural integrity without a change of the function and natural frequency before and after seismic loads.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.231-239
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• 1999

An improved version of current-regulated delta modulator (CRDM) is investigated for the output cunent control of v voltage-source inverters that have transformer-coupled series resonant load and are operated at the resonant frequency. Conventional CRDM has not only CUlTent offset problem but also transformer flux saturation problem when i it is applied to induction heating systems that have transformel-coupled loads. To cope with these problems, the effect of flux saturation is analysed, and simple method to av이d the problem is proposed. And integral type of CRDM is a adopted to remove the cunent offset. The boundaries of integrator gain for stable operation is calculated using the c concept of sliding mode controL The validity of proposed strategy is vel퍼ed through simulations and prototype e experiments.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.283.1-283
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• 2001

• Journal of Magnetics
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• v.21 no.4
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• pp.586-592
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• 2016

The magnetic-jack type CRDM withdraws or inserts a control rod assembly from/to the reactor core to control the core reactivity. The CRDM housings form not only the path of the electromagnetic field but also the pressure boundary of a nuclear reactor, and a periodic in-service inspection should be carried out if there are welded or flange jointed parts on the pressure boundary. The in-service inspection is a time-consuming process during the reactor refueling, and moreover it is difficult to perform the inspection over the reactor head. A magnetic motor housing is applied for the current SMART CRDM and has several welding joints, however a nonmagnetic motor housing with fewer or no welding joints may improve the operational efficiency of the nuclear reactor by avoiding or simplifying the in-service inspection process. Prior to the development, the magnetic field transfer efficiency of the nonmagnetic housing was required to be assessed. It was verified and optimized by the electromagnetic analysis of the lifting force estimation. Magnetic flux rings were adopted to improve the efficiency. In this paper, the design and optimization process of a nonmagnetic motor housing with the magnetic flux rings for the SMART CRDM are introduced and the analyses results are discussed.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.571-574
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• 2003

This paper proposes a detection method for mechanically stuck control rod drive mechanism (CRDM) faults. During the normal operation of a CRDM, disturbance voltage is induced due to the change of the airgap flux between the stator and the armature of a CRDM. This disturbance voltage is estimated by using $H_\infty$ filtering method, and generalized plant is used in linear fractional transform (LFT) framework. $H_\infty$ filtering is described and solved in terms of linear matrix inequalities (LMIs). Simulation results are shown.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1337-1345
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• 2011

In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor$r_o$/t, geometry of fillet, and adjacent nozzle.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.66-68
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• 2005