Ji-Sup Yoon

An Electrochemical Reduction of Uranium Oxide in the Advanced Spent-Fuel Conditioning Process

Abstract The Korea Atomic Energy Research Institute is currently developing the Advanced Spent-Fuel Conditioning Process (ACP) based on a pyrochemical process. An electrochemical reduction process has been developed as a key unit of the ACP. In this work, an electrochemical reduction of U3O8 powder in a LiCl-Li2O molten salt has been investigated in an electrochemical cell with a unique cathode assembly, which consists of a porous magnesia membrane, oxide powder, and a solid electricity conductor. The experimental results suggest successful demonstration of this process, exhibiting a reduction conversion of U3O8 of >99% for a batch.

Hybrid robust controller design for a two mass system with disturbance compensation

In this paper we describe a robust control method for when a torque or inertia change in a two mass system. There are various controllers that represent a robustness. Especially, the disturbance observer (DOB) and H infin of them are well known for their efficiency with respect to a disturbance rejection. Actually, there is method to make use of two controllers together as a cascade type. But the performance of this control is not efficient due to a fault in that the system degree increases when it designs a controller. In this paper, a hybrid type disturbance compensation is proposed for robust control methods. Basically, a hybrid robust controller is driven by the H infin controller, and a H infin control of the limited scope of a control for a disturbance when compared with the disturbance observer (DOB) will be compensated for by the H infin control input. We performed a DOB and H infin comparison simulation to prove the performance of the controller that is proposed in this paper. We performed simulations for a change in the torque and inertia and found that the proposed controller showed a small error. For a verification, we performed simulations by using MATLAB/SIMULINK.

Simulation of remote manipulator using a virtual engineering

This study deals with the design and establishment of a modeling and simulation tool for an evaluation of the accessibility and operability of a remote manipulation in an advanced spent fuel conditioning process facility. This article describes different kinds of modules to analyze and evaluate the behavior of a manipulator and proposes a system architecture which illustrates an interface between its modules. The mathematical background in relation to forward and inverse kinematics for a virtual manipulator to access the devices is explained. To find out if a virtual manipulator by using a 6-DOF haptic device could access a failed part of pyroprocessing devices, and if a human operator could feel the force feedback when it collides with other objects when accessing a device, a case study was carried out.

Design of remotely operated vol-oxidizer for hot-cell application

A high-capacity vol-oxidizer which can handle a several hundred kgHM/batch is being developed to supply U3O8 powders to an electrolytic reduction reactor. In this paper, we deal with the development of remotely operated vol-oxidizer that can convert UO2 pellets to U3O8 powders for hot-cell application. In order to develop this remotely operated vol-oxidizer, we proposed a design process and modular design for the remote operation in hot-cell, and the device has been modified by these modular design points and the design drawings have been presented. The design process consists of steps such as a mechanism device design, an engineering design and thermal analysis. To design the main mechanisms of the 1st step, we evaluated various mechanical (slitting, ball mill, roller straightening) and chemical methods (muffle furnace, rotary kiln). In the engineering design of the 2nd step, we calculated required volumes according to various weights and lengths of rod-cuts to design the reactor size. In the 3rd step, by using the modeling and analysis SWs (SolidWorks, COSMOSWorks), we built a 3D-modeling and performed an analysis of the main mechanisms for the safety design. We have selected the target modules of this devices such as heater, utility, motor, reactor, valve and outlet. The remote assembling and disassembling possibilities of the selected modules have been analyzed from the viewpoints of visibility, interference, approach, weight, and so on. We presented finally modular design suited to the above viewpoints.

Optimal Static Output Feedback Control of Tendon Driven Master-Slave Manipulator

In this work, a bilateral control for a master-slave manipulator system which will be used for handling objects contaminated by radioactivity has been addressed. The links of manipulators are driven independently by individual motors installed on the base and the driving torque is transmitted through pre-tensioned tendons. The measurable variables are the positions and rates of master/slave motors. In the consideration of the flexibility of the tendon and available measurements for control, we proposed an optimal static output feedback control for possible bilateral control architecture. By using modal analysis, the system model is reduced to guarantee the detectability which is a necessity for the static output feedback control design. Based on the reduced model, the control gains are determined to attenuate vibration in the sense of optimality. The feasibility of the proposed control design was verified along with some simulation results.

Spent Nuclear Fuel Disposal and Recycling Process and Its Operational Experience

Korea Atomic Energy Research Institute (KAERI) has been developing an advanced spent fuel conditioning process (ACP) to reduce the volume of spent fuel, and the construction of an ACP facility (ACPF) for a demonstration of its technical feasibility has been completed. In 2006 two inactive demonstrations were performed with simulated fuels in the ACPF. Accompanied by process equipment performance tests, its remote operability and maintainability were also tested during that time. Procedures for remote operation tasks are addressed well in this study and evaluated thoroughly. Also, remote maintenance and repair tasks are addressed regarding some important modules with a high priority order. The above remote handling tests results provided a lot of information such as items to be revised to improve the efficiency of the remote handling tasks. This paper deals with the current status of the ACP in Korea and the progress for remote handling in the ACPF.

Simulation of an Operator's External Dose using Computer Graphics

An optimization of a dismantling process should be at the beginning of a study for an evaluation of the radioactivity inventory and the safety of the workers. Many countries have been studied an optimization to achieve a shortened dismantling schedule, a reduction of an amount of waste, and cut down on the decommissioning by using computer graphics such as animation, simulation, and virtual reality. In this article, we provided methods for identifying an existence of radioactivity which is contained in the dismantling objects and for estimating a workers dose through a simulation. To estimate a workers external dose under a virtual dismantling environment which was produced by computer graphics, the shape of the thermal column by 3D CAD was created and the radiation dose surrounding the object was calculated by using MCNP. An animation that can demonstrate a dismantling procedure according to a dismantling scenario was produced. For matching the radiation dose which was calculated by MCNP-4C with an area where workers are dismantling a door on the animation, a simulation module which can show a workers external dose in a real-time was developed. The result from the distribution of the radioactivity enables us to distinguish where the most contaminated part of the dismantling objects was. In the animation, a virtual worker demonstrated a dismantling activities procedure as a chosen scenario. In the simulation, a workers exposure dose rate in a real-time as an intended in the design stage has been evaluated.

Master-slave manipulator aided remote decontamination system

This paper describes the development of a remote decontamination system for use in the highly radioactive zone of the ACP (advanced spent fuel conditioning process) hot-cell at the Korea Atomic Energy Research Institute. The remote decontamination system was designed and developed to remotely clean the contaminated in-cell floor and walls and equipments surface where, as the hot-cell is active, a direct human access to the in-cell is not possible due to the high radioactivity level. The remote decontamination system is remotely operated with the aid of mechanical or bilateral master-slave manipulators located in the ACP hot-cell. The remote decontamination system, employing a vacuum cleaning method, consists of four replaceable units. Each unit was designed as modules to facilitate in a maintenance by a remote manipulation by using master-slave manipulators. This decontamination system has an ability to remotely collect contaminated particles of up to 0. 3 microns by employing a four stage filtration structure. The design considerations and capabilities of the remote decontamination system from a remote operation and maintenance viewpoint are also presented.

Design of a virtual engineering environment and an evaluation of an operator’s behavior

The purpose of this study is to provide a basis for a minimization of a workers dose during dismantling activities. In the present study, we proposed methods for identifying an existence of radioactivity which is contained in dismantling objects and for evaluating a workers dose under a virtual dismantling environment. As a basic study to minimize a radiation exposure, we calculated the exposure dose by using the MCNP-4C as a worker dismantled an object in a radiation field. Secondly, we implemented animation and simulation modules to simulate a workers dose in a real-time. The radiation field of the thermal column door was visualized three dimensionally by using the radiation dose that was calculated by the code. The results show that it can simulate various kinds of dismantling activities and simultaneously view the exposure dose level in a real-time according to dismantling activities through an animation and simulation.

Development of a Bridge Transported Servo Manipulator System for the Remote Operation and Maintenance of Advanced Spent Fuel Conditioning Process

The Advanced Spent Fuel Conditioning Process(ACP), which is the process of the reduction of uranium oxide by lithium metal in a high temperature molten salt bath for spent fuel, was developed at Korea Atomic Energy Research Institute (KAERI). Since the ACP equipment is located in an intense radiation field (hot cell) as well as in a high temperature, it must be remotely operated and maintained. The ACP hot cell is very narrow so the workspace of the wall-mounted mechanical Master-Slave Manipulators(MSMs) is restricted. A Bridge Transported Servo Manipulator(BTSM) system has been developed to overcome the limitation of an access that is a drawback of the mechanical MSMs. The BTSM system consists ot a bridge crane with telescoping tubeset, a slave manipulator, a master manipulator, and a control system. We applied a bilateral position-position control scheme with friction compensation as force-reflecting controller. In this paper, the transmission characteristics on the tendon-and-pulley train is numerically formulated and analyzed. Also, we evaluate the performance of the force-reflecting servo manipulator.