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[en] As part of a fundamental study on the volume reduction of contaminated concrete wastes, the separation characteristics of the aggregates and the distribution of the radioactivity in the aggregates were investigated. Radioisotope 60Co was artificially used as a model contaminant for non-radioactive crushed concrete waste. Volume reduction for radioactively contaminated dismantled concrete wastes was carried out using activated heavy weight concrete taken from the Korea Research Reactor 2 (KRR-2) and light weight concrete from the Uranium Conversion Plant (UCP). The results showed that most of the 60Co nuclide was easily separated from the contaminated dismantled concrete waste and was concentrated mainly in the porous fine cement paste. The heating temperature was found to be one of the effective parameters in the removal of the radionuclide from concrete waste. The volume reduction rate achieved was above 80% for the KRR-2 concrete wastes and above 75% for the UCP concrete wastes by thermal and mechanical treatment
[en] The evaluation of decommissioning scenarios is critical to the successful development and execution of a decommissioning project. This paper presents the logical method that is the analytic hierarchy process for selecting a decommissioning scenario. The AHP provides a structure on decision-making processes where there are a limited numbers of choices but each as a number of attributes. In this study, the AHP model to evaluate decommissioning scenarios reflecting quantitative and qualitative considerations is presented. This AHP model is implemented for the two candidate scenarios of the thermal column in KRR-1 to find the better scenario. The weightings of each criteria and subcriteria and the quantitative figures about both scenarios were obtained
[en] At present, two research reactors are operated at the Korea Atomic Research Institute, namely, one being a TRIGA Mark-II reactor of 250-kW power rating and the other a TRIGA Mark-III reactor of 2 MW, both of General Atomic design. Design characteristics and operations for the reactors are reviewed
[en] Optimum solidification for slurry waste, produced during the operation of KRR-1 and 2, with ordinary Portland cement was investigated. Waste form was prepared by changing the ratio of slurry waste/water/cement. Waste forms were evaluated by workability test, compressive strength test, free standing water test, and immersion test. The experimental results showed that the optimum mixing ratio of slurry waste (dry wt)/water/cement(dry wt) was found to be 0.32/0.34/0.34. The effect of the chemical (EDTA complex, low conc.) in water on waste forms was insignificant
[en] During the decommissioning activities of the KRR-1 and 2 (Korea Research Reactor 1 and 2) and UCP (Uranium Conversion Plant), all information and data, which generated from the decommissioning project, were record, input and managed at the DECOMMIS (DECOMMissioning Information management System). This system was developed for the inputting and management of the data and information of the man-power consumption, operation time of the dismantling equipment, the activities of the radiation control, dismantled waste management and Q/A activities. When a decommissioning is planed for a nuclear facility, an investigation into the characterization of the nuclear facility is first required. The results of such an investigation are used for calculating the quantities of dismantled waste volume and estimating the cost of the decommissioning project. That is why, the DEFACS (DEcommissioning FAcility Characterization DB System) was established for the management of the facility characterization data. The DEWOCS (DEcommissioning WOrk-unit productivity Calculation System) was developed for the calculation of the workability on the decommissioning activities. The work-unit productivities are calculated through this system using the data from the two systems, DECOMMIS and DEFACS. This result, the factors of the decommissioning work-unit productivities, will be useful for the other nuclear facility decommissioning planning and engineering. For this, to set up the items and plan for the decommissioning of the new objective facility, the DEMOS (DEcommissioning work Modeling System) was developed. This system is for the evaluation the cost, man-power consumption of workers and project staffs and technology application time. The factor of the work-unit productivities from the DEWOCS and governmental labor cost DB and equipment rental fee DB were used for the calculation the result of the DEMOS. And also, for the total system, DES (Decommissioning Engineering System), which is now developing for the decommissioning design and plan
[en] Experimental result on power control for a research reactor is presented. Considering various design features for reactor safety, we developed a simple and easy-to implement controller with a limiting function of power change- rate as well as fine tracking performance. The proposed controller has been designed, simulated, and applied to TRIGA-II type research reactor successfully. A power control method for a TRIGA-II type research reactor has been designed, simulated, and applied to actual reactor. The control performance during commissioning test shows that the proposed controller provides fine control performance for various changes in reference values (PDM). Further research may include model-based approach with proper robustness to disturbances.
[en] The computer system for the characterization on the nuclear facilities is established as the name of the DEFACS (DEcommissioning FAcility Characterization DB System). his system is consist of the four main part with the grouping of the items and it's code creation and management system, data input system, data processing and data out put system. All the data was processed by a simplified and formatted manner to provide useful information to the decommissioning planner. The four nuclear facilities are objected for the system; the KRR-1 and 2 (Research reactor), Uranium conversion plant (Nuclear chemical plant), UF4 pilot plant and the North Korea nuclear facility (5MWe Research Reactor). All the data from a nuclear facility was categorized and inputted into the several data fields in the input system, which were chosen by considering the facility characteristics. All the hardware is workstation for Web and DB server and PC grade computers for the users and the software 'ORACLE, RDBMS 11g' operated on the WINDOW 2008 O/S, was selected
[en] Irradiated graphite arising from the decommissioning of KRR-2 (Korean Research Reactor 2) have shown to include somewhat degree of Wigner energy, specific radioactivity and the resulting radioactive chemicals/nuclides in the study of bulk mode of graphite structure. Plans of annealing and disposal of the irradiated graphite stored Wigner energy in its internal matrix of rearranged carbon structures due to neutron dose might depend on whether the storage stability of the graphite is attainable or not. That is, because the Wigner energy as a latent explosive energy in the graphite structure was caused by carbon atomic rearrangements or dimensional distortions in the graphite crystal lattice is very labile at higher temperature conditions than that of its formation, why it is of importance to forecast the thermal stability of the graphite in a long term storage. Moreover, since the nuclide emissions are directly related to the thermal stability of the graphite at the same time in view point of graphite disposal, the control of Wigner energy content in a lower level or naught in the waste program of the irradiated graphite might be necessary in the near future. A study on fire accident model as an emergency case analysis at a sudden external fire exposure of the irradiated graphite was proposed to assess the feasibility of the disposal storage of the graphite without any physical and/or chemical treatment of Wigner energy in the form of box disposal. In this study a fire accident model of the irradiated graphite, that is to be disposed in the radioactive waste storage facility in the forthcoming time, was considered to estimate the thermal stability of graphite, whether the Wigner energy of the irradiated graphite has an effect on the storage stability or not, in front of a sudden fire accident
[en] During the decommissioning activity of TRIGA Mark-II research reactor(the first research reactor in Korea), a decontamination of the reactor coolant system will be performed in order to reduce the risk of contaminants release and public exposure when opening the reactor as a memorial museum. The reactor coolant system decontamination technology for the decommissioning of TRIGA reactors is under development at KAERI (Korea Atomic Energy Research Institute). In this paper, an overview of the technology under development and demonstration plan by using the chemical decontamination technology is introduced. Also, the recent laboratory test results that the fluoboric acid based reagent showed the effective dissolution behaviours of aluminium material even in dilute concentration at low temperature, and an applicability to the decontamination of unrestricted release are introduced
[en] The first KAERI neutron radiography facility, which was installed at the research reactor KRR-2(2MW) in early 1980's to utilize for the inspection of the nuclear and non-nuclear objects, was closed at the end of 1995. As a continued programme, a new neutron radiography facility has been installed at HANARO with various upgrades. In this article, its design features, performance characteristics and utilization programme are outlined.