• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.243-253
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• 2021

In the dismantling process of a reactor coolant system (RCS) piping, a radiation protection plan should be established to minimize the radiation exposure doses of dismantling workers. Hence, it is necessary to estimate the individual effective dose in the RCS piping dismantling process when decommissioning a nuclear power plant. In this study, the radiation exposure doses of the dismantling workers at different positions was estimated using the MicroShield dose assessment program based on the NUREG/CR-1595 report. The individual effective dose, which is the sum of the effective dose to each tissue considering the working time, was used to estimate the radiation exposure dose. The estimations of the simulation results for all RCS piping dismantling tasks satisfied the dose limits prescribed by the ICRP-60 report. In dismantling the RCS piping of the Kori-1 or Wolsong-1 units in South Korea, the estimation and reduction method for the radiation exposure dose, and the simulated results of this study can be used to implement the radiation safety for optimal dismantling by providing information on the radiation exposure doses of the dismantling workers.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.45-51
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• 2023

During the operation of a nuclear power plant (NPP), the waste reactor vessel closure head (RVCH) that is replaced owing to design or manufacturing defects is buried in a designated area or temporarily stored in a radiation shielding facility within the NPP. In such cases, storing it for extended periods proves a challenge owing to space constraints in the power plant and a safety risk associated with radiation exposure; therefore, dismantling it quickly and safely is crucial. However, not much research has been done on the dismantling of the RVCH in an operational power plant. This study proposes a dismantling process based on the radioactive contamination level measured for the Kori #1 RVCH, which is currently being discarded and stored, and examines the decontamination and cutting according to this process. In addition, the amount of secondary waste and dismantling cost are evaluated, and the dismantling effect of the reactor closure head is analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.848-851
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• 1997

A graphic simulation program is developed to assimilate the remote dismantling process of research nuclear reactors. This program makes extensive use of a commercial robot graphic instruction program. Firstly, a realistic graphic model of research reactors are built along with various dismantling equipments. Using the graphic instruction languages provided by IGRIP, then, a graphic process simulation program is developed that operates interactively with the user. Consequently, it is made possible for a process designer to visualize an arbitrary dismantling sequence and interactively modify the process. It is expected that the developed system will be utilized as an effective operator aid in both design and execution phases of remote dismantling of research reactor.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.355-367
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• 2017

The decommissioning of Kori unit 1, which was permanently shut down in June of 2017, will be the first instance of the dismantling of a commercial nuclear power plant in Korea. The disposal of waste during the dismantling process accounts for a large part of the total decommissioning cost. Therefore, structures consisting of activated and contaminated concrete must be economically and safely dismantled by establishing a proper dismantling strategy. This study focuses on optimized dismantling and disposal scenarios pertaining to a biological shield. Several dismantling cases, regulations and technologies related to waste treatment as these practices pertain to nuclear power plants are analyzed. To minimize the amount of waste from the biological shield dismantling process, an optimized dismantling scenario is presented and disposal alternatives for dismantled concrete waste are proposed.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.525-533
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• 2017

A new concept termed the Innovative Nuclear Power Plant Building Arrangement (INBA) strategy is a new nuclear power plant building arrangement method which encompasses upfront consideration of more efficient decommissioning. Although existing decommissioning strategies such as immediate dismantling and differed dismantling has the advantage of either early site restoration or radioactive decommissioning waste reduction, the INBA strategy has the advantages of both strategies. In this research paper, the concept and the implementation method of the INBA strategy will be described. Two primary benefits will be further described: (1) early site restoration; and (2) radioactive waste reduction. Several other potential benefits will also be identified. For the estimation of economic benefit, the INBA strategy, with two primary benefits, will be compared with the immediate dismantling strategy. The effect of a short life cycle nuclear power plant in combination with the INBA strategy will be reviewed. Finally, some of the major impediments to the realization of this strategy will be discussed.

• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.606-612
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• 2018

Many nuclear power plants in Japan are approaching the end of their planned operational life spans. They must be decommissioned safely in the near future. Using augmented reality (AR), workers can intuitively understand information related to decommissioning work. Three-dimensional (work-site) reconstruction models of dismantling fields are useful for workers to observe the conditions of dismantling field situations without visiting the actual fields. This study, based on AR and work-site reconstruction models, developed and evaluated an information reference system. The evaluation consists of questionnaires and interview surveys administered to six nuclear power plant workers who used this system, along with a scenario. Results highlight the possibility of reducing time and mitigating mistakes in dismantling fields. Results also show the ease of referring to information in dismantling fields. Nevertheless, it is apparently difficult for workers to build reconstruction models of dismantling fields independently.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2085-2091
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• 2020

The license for Kori-1, the first commercial reactor in Busan, Korea, was terminated in June 2017; therefore, preparations are being made for its decommissioning. Because the radioactivity of Bio-shield varies greatly throughout the structure, the doses received by the workers depend on the location, order, and duration of dismantling operations. Thus, a model for evaluating the worker external dose during the dismantling of the Kori-1 bio-shield was developed, and work scenarios for dose assessment were designed. The Dose evaluation code VISIPLAN was used for dose assessment. The dose rate around the bio-shield was evaluated and the level of exposure to the operator was evaluated according to the work scenario. The maximum annual external dose was calculated as 746.86 mSv for a diamond wire saw operator under dry cutting conditions, indicating that appropriate protective measures, such as changing dismantling sequence, remote monitoring, shield installation, and adjustment of work team are necessary for the safe dismantling of the bio-shield. Through these protective measures, it was found that the worker's dose could be below the dose limit.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.3
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• pp.297-306
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• 2021

In this study, basic strategies for the decommissioning and site remediation of the Fukushima Daiichi Nuclear Power Station (FDNPS) were investigated. Six scenarios were formulated based on two of the three decommissioning strategies of nuclear power plants defined by the International Atomic Energy Agency (IAEA): immediate dismantling and deferred dismantling. A multicriteria decision analysis was performed to analyze the preferences of the options from the viewpoints of the timeframe to complete decommissioning, the resulting waste, the site usability, and the availability of the radioactive waste disposal route. The same six scenarios were applied to both the FDNPS and the nuclear power plants that ceased operation after a normal plant life cycle for comparison. For the FDNPS, the decommissioning project involved fuel debris retrieval, dismantling, and site remediation. The analysis results suggest that the balance between the amount of waste and the time to achieve the end state may be one of the most critical factors to consider when planning the decommissioning and site remediation of the FDNPS.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.73.1-73
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• 2001

To utilize the uranium resources contained in the spent nuclear fuel generated from the nuclear power plants, the remote handling and dismantling technology is required. The dismantling process of the sport fuel is the most common process involved in the spent fuel recycling, the rod consolidation and the disposal processes. Since the machine used in the dismantling process are located and operated in isolated space, so called a hot cell, the reliability of machines is very important. To enhance the reliability of the process, in this research, the graphical monitoring system is developed for the fuel dismantling process. The graphic model of each machine is composed of many parts and every parts of the graphic model are given their own kinematics. Using the kinematics and simulating the graphic model in the virtual environment, the validity of the conceptual design can be verified before ...

• Nuclear Engineering and Technology
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• v.44 no.5
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• pp.507-522
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• 2012

When decommissioning a nuclear power plant, it is difficult to make an appropriate plan to ensure sufficient space for temporary placement and conveyance operations of dismantling targets. This paper describes a system to support temporary placement and conveyance operations using augmented reality (AR). The system employs a laser range scanner to measure the three-dimensional (3D) information of the environment and a dismantling target to produce 3D surface polygon models. Then, the operator simulates temporary placement and conveyance operations using the system by manipulating the obtained 3D model of the dismantling target in the work field. Referring to the obtained 3D model of the environment, a possible collision between the dismantling target and the environment is detectable. Using AR, the collision position is presented intuitively. After field workers evaluated this system, the authors concluded that the system is feasible and acceptable to verify whether spaces for passage and temporary storage are sufficient for temporary placement and conveyance operations. For practical use in the future, some new functions must be added to improve the system. For example, it must be possible for multiple workers to use the system simultaneously by sharing the view of dismantling work.