Ho Dong Kim

Development of an overhead crane for remote handling tasks at nuclear facility

An overhead crane with telescopic motion was developed to transport servo-manipulator for remote handling tasks in the PyRoprocess Integrated inactive DEmonstration facility (PRIDE). The overhead crane consists of a telescope, trolley system, cabling management system, girder and rotation interface. The telescope of the overhead crane was designed as a cylindrical pipe-based tube type in order to increase the bending and twisting rigidity and it has a long extended length and short retracted length. The cabling management system was designed to be compact in size in order to accommodate the changed cable length according to the telescopic motion. All drive modules were designed to have spare modules in order to prepare for emergencies. As design verification process, structural analysis was performed on some important modules. Currently, the overhead crane is installed at a test bay in KAERI, and it is being tested.

Radioactive waste arisings from various fuel cycle options

This study examines all kinds of waste volumes from various fuel cycle options including DUPIC (Direct Use of Spent PWR Fuel In CANDU) fuel cycle and compares each other. The fuel cycle option considered the PWR (Pressurized Water Reactor) once-through cycle, the PHWR (Pressurized Heavy Water Reactor) once-through cycle and the thermal recycling option using an existing PWR with MOX (Mixed Oxide) fuel. This study focuses on the radioactive wastes including mill waste, low-level waste and high-level waste generated by all fuel cycle steps, which can be one of the effectiveness measures of waste management. All waste disposition volume is estimated in terms of m3/GWe-yr. We find in the estimation of radioactive waste volume that PWR-MOX option has the lowest mill tailings and spent fuel volumes among the options, but the option has high volume of ILW and HLW. Mill tailings and spent fuel volumes of the DUPIC fuel cycle are lower than those of other competitive options such as PWR-PHWR once-through cycle. PWR once-through cycle has the lowest LLW and ILW volume among the options, but has high mill tailings and spent fuel volume. The data obtained in this study would be helpful to further estimate environmental effect and/or waste disposition costs in various fuel cycle options.

Analysis of Nuclear Proliferation Resistance of DUPIC Fuel Cycle

This study compares the proliferation resistance of DUPIC (Direct Use of Spent PWR Fuel in CANDU) fuel cycle with other fuel cycle cases. The other fuel cycles considered in this study are PWR of once-through mode (PWR-OT), PWR of reprocessing mode (PWR-MOX), in which spent PWR fuel is reprocessed and recovered plutonium is used for making MOX (Mixed Oxide), CANDU with once-through mode (CANDU-OT), PWR fuel and CANDU fuel in a once- through mode with reactor grid equivalent to DUPIC fuel cycle (PWR-CANDU-OT). This study is focused on intrinsic barriers, especially, radiation field of the diverted material, which could be a significant accessibility barrier, amount of special nuclear material based on 1 GWe-yr that has to be diverted and the quality of the separated fissile material. It is indicated from plutonium analysis of each fuel cycle that the MOX spent fuel is containing the largest plutonium per MTHM but PWR-MOX option based on 1 GWe-yr has the best benefit in total plutonium consumption aspects. The DUPIC option is containing a little higher total plutonium based on 1 GWe-yr than the PWR-MOX case, but the DUPIC option has the lowest fissile plutonium content which could be another measure for proliferation resistance. On the whole, the CANDU-OT option has the largest fissile plutonium as well as total plutonium per GWe-yr, which means negative points in nuclear proliferation resistance aspects. It is indicated from the radiation field analysis that fresh DUPIC fuel could play an important radiation barrier role, more than even CANDU spent fuels. In conclusion, due to those inherent features, the DUPIC fuel cycle could include technical characteristics that comply naturally with the Spent Fuel Standard, at all steps along the DUPIC linkage between PWR and CANDU.

Advantages of Irradiated DUPIC Fuels from the Perspective of Environmental Impact

Abstract This study compares some properties of irradiated Direct Use of Spent Pressurized Water Reactor (PWR) Fuel In Canada Deuterium Uranium reactor (CANDU) (DUPIC) fuels with properties of other fuel cycles. The properties include the radiotoxicity, decay heat, activity, and actinide content embedded in various spent fuels or high-level wastes, which could be measures of the effectiveness of waste management. From radiotoxicity analysis of fuel cycles, the toxicity of the DUPIC option based on 1 GW(electric)·yr is much smaller than those of other fuel cycle options such as the PWR once-through mode, mixed oxide fuel recycling mode, and CANDU once-through mode. The analysis shows that the value is just about half the order of magnitude of other fuel cycles until decayed to a level below the toxicity of initial ore. This means that the DUPIC option could have an indirect benefit on the environmental effects of long-term spent-fuel disposal. From total activity analysis of various fuel cycle options, the activity per metric ton heavy metal of spent fuel is the lowest in natural uranium CANDU fuel, but in the case of activity based on 1 GW(electric)·yr, the DUPIC option has the smallest activity. In the meanwhile, from the activity analysis of 99Tc and 237Np, which are important to the long-term transport in geologic media, the DUPIC option was being contained in only about half of those other options. In conclusion, compared to other fuel cycle cases, the irradiated DUPIC fuels would have good properties from the perspective of environmental effects.

Electrical circuit model for quantifying the proliferation resistance of nuclear fuel cycles

Abstract For quantifying the proliferation resistance of nuclear fuel cycles, the proliferation resistance index was modeled in imitation of an electrical circuit and linked with multi-attribute utility theory. As a case study, this model was applied to Korean nuclear fuel cycle alternatives including DUPIC(Direct Use of spent PWR fuel In CANDU) fuel cycle. The main features of the model are that political issues as well as technical issues relevant to the proliferation resistance can be included, and also all facilities and activities in a specific nuclear fuel cycle, from mining to disposal, can be considered. It appeared that the resistance index derived using an electrical circuit concept could be used as an international measure for the risk of nuclear proliferation. From the case study, it seems that the DUPIC fuel option in Korea could be strongly competitive with the reprocessing option in respect of nuclear proliferation resistance.

Development of a control system for master-slave operation

A prototype of a master-slave servo manipulator system has been developed for the use in the PRIDE (PyRoprocess Integrated inactive DEmonstration) facility where the integrated performance of full pyroprocess flow will be verified. The PRIDE facility is designed to have an argon-atmosphere cell which prohibits direct access by human operators. Therefore, all the operation and maintenance of the process equipment is performed remotely through a master-slave manipulation. In this work, we present the development of a remote control system for a bridge transported dual arm servo-manipulator.

Development of a bridge transport system with telescopic motion

A bridge transport system with telescopic motion was developed to transport servo-manipulator for remote handling tasks in PyRoprocess Integrated inactive DEmonstration facility (PRIDE). The bridge transport system consists of telescope, trolley system, cabling management system, girder and rotation interface. The telescope of the bridge transport system was designed as a cylindrical pipe-based tube type in order to increase bending and twisting rigidity and it has a long extended length and short retracted length. The cabling management system was design to have compact size but to accommodate changed cable length according to telescopic motion. All drive modules were designed to have spare modules to prepare for emergency. As design verification process, structural analysis was performed on some important modules. Currently, the bridge transport system with telescopic motion is installed at a test bay in KAERI, and it is being tested.

Design and fabrication of a servo-manipulator for use in the PRIDE facility

This paper describes the design and fabrication of a cable-driven dual arm master-slave servo-manipulator. The cable transmission has been selected because it greatly reduces the weight and friction, and it also allows realizing a backlash-free actuation. However, it causes a motion coupling problem due to unwanted motion interference at the joints. In this work, we solve this problem through a novel motion decoupling mechanism. Also, a simple balancing method based on potential energy equilibrium has been proposed to counterweight 3-axis motion such as pitch and roll of upper arm, and pitch of forearm.

Time-Domain Noise Analysis of 8-Channel CMOS Readout Circuits for CZT X-Ray Detector Array

An 8-channel CMOS low-noise readout IC is designed for CdZnTe (CZT) X-ray detector arrays. Each channel of the IC is composed of a continuously discharged preamplifier and a comparator. The preamplifier is operated in pulse-mode and this is realized with a feedback capacitor and a pair of MOSFETs. The noise of this readout IC is calculated by the time-domain Hspice noise simulation. The calculated RMS total noise voltage at the output node of the preamplifier is 0.246 mV. The prototype chip is fabricated by 1.5 um CMOS technology through MO SIS and the measured noise voltage of the preamplifier output is 0.435 mV.

Time-Domain Noise Analysis of CMOS Readout Ic for CZT X-Ray Detectors

We present the low noise design of an 8-channel CMOS fast readout circuit for CZT (CdZnTe) x-ray detectors. The one channel of the readout circuit is composed the continuous discharged preamplifier, the gain amplifier and the comparator. The Hspice noise simulations are performed in the time domain. The calculated RMS noise voltages of the gain stage output for the time domain is 15.5 mV. A test chip has been fabricated by using AMI (American Microsystems, Inc.) 1.5 μm low-noise analog CMOS process through the MOSIS service. The measured RMS noise voltage of the gain stage output is 23.5 mV. The charge-to-voltage gain of this readout ASIC is 130 mV/fC and the signal to noise ratio at the gain stage output is 34. Introduction We have been studying a low-noise design of a multichannel CMOS readout ASIC for CZT detector arrays for the x-ray or gamma-ray. CZT detectors have demonstrated both good energy and spatial resolution in the fields such as the medical imaging, the space science and so forth because of their high detection efficiency and low dark current in the room temperature [1]. For the imaging application, several multi-channel CMOS readout circuits have been designed and are continuously being made now. In this study, we design an 8-channel CMOS readout IC for the x-ray counting application of CZT pixel arrays. The requirements for this circuit are (a) the detector capacitance CD = 5pF, (b) the counting speed more than 10 6 photons/s, (c) the signal-to-noise ratio more than 20:1, and (d) the charge-to-voltage gain of at least 100 mV/fC. Design of Readout ASIC Basic Blocks. The multi-channel preamplifier/comparator circuit of this study has performance characteristics such as low noise and fast counting-mode application. The one-channel is composed of the preamplifier, the gain amplifier, and the comparator circuits as shown in Fig. 1. Fig. 1. The block diagram of the one-channel of the readout circuits including four main noise sources Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 239-244 doi:10.4028/www.scientific.net/KEM.270-273.239