• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.559-568
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• 2017

Objective: The aim of this study is to investigate the effective managerial factors influencing dose reduction of the nozzle dam installation and removal tasks ranking within top 3 in viewpoint of average collective dose of nuclear power plant maintenance job. Background: International Commission on Radiation Protection (ICRP) recommended to reduce unnecessary dose and to minimize the necessary dose on the participants of maintenance job in radiation fields. Method: Seven sessions of nozzle dam installation and removal task logs yielded a multiple regression model with collective dose as a dependent variable and work time, number of participants, space doses before and after shield as independent variables. From the sessions in which a significant reduction in collective dose occurred, the effective managerial factors were elicited. Results: Work time was the most important factor contributing to collective dose reduction of nozzle dam installation and removal task. Introduction of new technology in nozzle dam design or maintenance job is the most important factor for work time reduction. Conclusion: With extended task logs and big data processing technique, the more accurate prediction model illustrating the relationship between collective dose reduction and effective managerial factors would be developed. Application: The effective managerial factors will be useful to reduce collective dose of decommissioning tasks as well as regular preventive maintenance tasks for a nuclear power plant.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1520-1524
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• 2004

This paper describes the development of a robotic maintenance system for use in a maintenance operation of the nozzle dam in a water chamber of a steam generator at the Kori nuclear power plant in Korea. The robotic maintenance system was designed to minimize the personnel exposure to a hazardous radioactive environment. This robotic maintenance system is operated by a teleoperated control which was designed to perform the nozzle dam maintenance tasks in a remote manner without endangering the human workers. Specific maintenance tasks involve the transportation, insertion, and removal of nozzle dams in a water chamber inside a steam generator via a narrow man-way entrance port. The developed robotic maintenance system has two major subsystems: a two degrees of freedom guiding device acting as the main guiding arm and a master-slave manipulator with a kinematic dissimilarity. The mechanical design considerations, control system, and capabilities of the robotic maintenance system are presented. Finally, a graphical representation of the nozzle dam maintenance processes in a simulated work environment are also demonstrated.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.327-335
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• 1995

The normal shutdown and maintenance period of a nuclear power plant can be remarkably shortened when the examination and maintenance works in steam generator tubes are simultaneously carried out with refueling job. There are nozzle dams to Hock the coolant How from reactor to steam generator. Workers are reluctant to install nozzle dam because of the high radiation exposure and the limited working space in steam generator. Moreover, the heavy weight of present nozzle dam makes it installation and removal works much difficult. In this paper, a lighter KAERI nozzle dam with increased flexural rigidity-to-weight was designed and manufactured by changing the structure design of the present nozzle dam and by selecting new material, carbon fiber-reinforced plastic.

• Elastomers and Composites
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• v.55 no.3
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• pp.222-228
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• 2020

Rubber materials, used in nuclear power plants, need high heat-oxidation resistance to curing or cracking under a heat aging environment. This is because they are applied to environments with high temperature, high humidity, and radiation exposure. Nuclear radiation causes additional hardening or degradation, therefore, rubber materials need radiation resistance that satisfies the general and any accidental conditions produced in the power plant. Therefore, in this study, we developed a rubber material with excellent heat and radiation resistance for the diaphragm seal of a nuclear steam generator nozzle dam. The rubber material greatly improved the reliability of the steam generator nozzle dam. In addition, 30 inch and 42 inch diaphragm seals were manufactured using the developed rubber material. A nozzle dam was installed in a nuclear power plant and tested under the same conditions as a steam generator to evaluate safety and reliability. In the future, the performance and safety of diaphragm seals developed through field tests of nuclear power plants will be evaluated and applied to currently operating and new nuclear power plants.

• 대한방사선방어학회:학술대회논문집
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• 2009.04a
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• pp.278-279
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• 2009

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.133-136
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• 1996

The nozzle dam task is essentially needed to maintain and repair nuclear power plants. For this task, an 8-dof redundant robot is studied with a local path-planning method[l] which is effective to find the optimal joint path in the constrained environment. In this paper, the method[l] is improved practically with the weight matrix and efficient algorithm to find working set. The effectiveness of the proposed method is demonstrated by simulation and animation.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.821-824
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• 1993

In hazardous conditions, where entry of human operators is restricted, such as high radiation regions in nuclear facilities, a lot of remote inspections and remote handling tasks must be performed. In this study, the stereo imaging system has been developed and the remote handling technique, has been studied to enhance the efficiency of tele-operation. The nozzle dam handling robot is one of the most important robots applied to nuclear facility. The robot will be equipped with the developed stereo imaging system. The stereo imaging system will outstandingly improve the tele installing/removal tasks for nozzle dam.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.571-576
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• 1996

Currently most nuclear power plants(NPPs) are adopted the mid-loop operation to minimize the overhaul period and save the operating cost. For mid-loop operation it is essential to install nozzle dam between RCS pipe and steam generator(SG). Because SG remains more highly contaminated with radioactive material than any other parts of the NPPs, the repairmen are very reluctant to carry out installing nozzle dam inside the SG. Until now, unfortunately, it appears that no practically applicable device was developed to provide the longstanding demand. Also the accidents have been reported by licenser event report during this operation mode due to loss of residual heat removal(RHR). The purpose of this paper is to conduct remotely blocking and disintegration of nozzle of a SG which has the highest radiation exposure during the maintenance in NPPs. The remote nozzle blocking device of a SG includes three bladders, hubs, air controller provisions to supply and contact air pressure into the bladders. This remote nozzle block device will give the larger operation margin to prevent the loss of RHR and minimize the radiation exposure dose to the repairman and shorten the overhaul periods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3871-3882
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• 1996

In this paper, a closed-form formulation for inverse kinematics of robot manipulators with kinematic redundancy under the constrained environment has been derived using the Kuhn-Tucker condition, the extended Lagrange multiplier method and the working set method. The proposed algorithm satisfies the necessaryand sufficient conditions for optimization subject to equality and inequality constraints. In addition, computationally efficient kinematic control methods have been proposed using differential kinemetics and gradient projection mehtod. The effectiveness of the proposed methods has been demonstrated with a 4-dof planar robot, and then a 7-dof spatial robot as a practical application to the nozzle dam task in the Nuclear Power Plant.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.657-662
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• 1996

Venting capability to prevent excess pressurization caused by loss of Residual Heat Removal System (RHRS) during mid-loop operation hat been evaluated analytically and the peak Reactor Coolant System (RCS) pressure was compared with the results of the MIDLOOP computer code. Even though analytical method if relatively simple, the results are in a good agreement with those of the computer code. For both methods, the peak pressures have not, exceeded the nozzle dam design pressure, if the vent paths such as pressurizer safety valves or a pressurizer manway are available in a closed RCS configuration with the nozzle dam installed.