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[en] As organic liquid waste, one of the hardly disposable radioactive wastes, has not been established for its treatment technology, the waste is temporarily stored in the research organizations or facilities. Although the use of incineration technology is known to be effective for the treatment of organic radioactive wastes, it is not possible for the general public to accept the environmental pollutants such as process corrosion and dioxin generated during the high temperature incineration process. Alternative oxidation technologies (AOTs) have been developed since the 1980s to improve various incineration processes. Typical incineration alternatives include catalytic chemical decomposition processes, direct chemical decomposition, oxygenation, steam reforming, gas phase reduction, and a method for the oxidation of hydrochloric acid. However, despite the long-term research of these treatment methods, about 14 tons of organic radioactive waste, including TBP, dodecane, cutting oil, waste oil, alcohol, and etc., which were generated during the operation of the research institute, were temporarily stored in the Radioactive Waste Disposal Facility (RWTF) at Korea Atomic Energy Research Institute (KAERI). Therefore, in order to treat these radioactive liquid wastes, we have recommended the treatment method using a sponge filter made of polymer or graphene which have micro- and macro-pores completely different from the conventional treatment methods. If the organic compounds can be separated from the organic radioactive wastes, it is possible to effectively treat the organic radioactive wastes with minimization of further occurring radwastes
[en] We develop a heat exchanger modules for a multi-burner boiler. The heat exchanger module is kind of a Heat Recovery Steam Generator (HRSG). This heat recovery system has 8 heat exchanger modules. The 1st module consists of 27 bare tubes due to high temperature exhaust gas and the others consist of 27 finned tubes. The maximum steam pressure of each module is 1 MPa and tested steam pressure is 0.7 MPa. In order to test these heat exchanger modules, we make a 0.5 t/h flue tube boiler (LNG, 40 Nm3/h). We tested the heat exchanger module with changing the position of each heat exchanger module. We measured the inlet and outlet temperature of each heat exchanger module and calculated the heat exchange rate. Based on test results, we develop a heat transfer calculation program to predict flue gas. Calculation results show that temperature and temperature difference between measured and calculated flue gas exit temperature is less than 20 .deg. C when flue gas inlet temperature is 620 .deg. C.
[en] As a part of R and D activities for the development of advanced fast reactors, HT9 cladding performance of Ultra long Cycle Fast Reactor (UCFR) is evaluated in various cladding peak temperatures and design power levels (1000MWe and 1000MWe). The key design concept of UCFR is a non refueling during 30 to 60 years operation, and this concept may require the maximum cladding temperature of ∼650 .deg. C peak cladding temperature and cladding radiation damage of over 200dpa (displacements pet atom). Therefore, for the design of UCFR, challenges such as thermal creep, irradiation creep and swelling must be quantitatively evaluated. As a cladding material, HT9 shows distinguishably favorable properties for UCFR, In this study, therefore, key design parameters for the cladding performance will be evaluated for UCFR cladding design and resulted the prediction of life time of cladding in UCFR
[en] Nickel based alloys have a good corrosion resistance and mechanical properties to tolerate harsh and extreme environments. However, the interaction of nickel and nickel based alloys with water and oxygen atom causes dissolution of metallic atom and diffusion of elements. After then, oxidation arises at the surface. Therefore, the formation of oxide layer is an unavoidable process in high temperature water environments. The oxidation process of nickel based alloys is at the origin of the initiation of stress corrosion cracking(SCC), Stress corrosion cracking is arisen from interaction of mechanical, metallurgical, and electrochemical factors. It can induce failure of structural materials. Hence, it is important to understand and solve stress corrosion cracking in nickel based alloys. Therefore, this study's objective is to understand effect of surface oxidation of nickel through the simulation of the diffusion processes of oxygen in nickel surfaces. This work was focused on the prediction of oxygen diffusion in order to understand the fundamental oxidation behavior of nickel. According to the results, oxygen atoms have small energy barrier for diffusion on nickel surface and lead to dissolution of metallic atom
[en] This work was focused on the investigation of early stage oxidation in order to understand the fundamental oxidation behavior of nickel by using first principle method and molecular dynamics. Also, ReaxFF reactive force field was modified potentials for Ni/O systems. Nickel based alloys are one of the most important structure materials in modern nuclear industry. Nickel based alloys have a good corrosion resistance and mechanical properties to tolerate harsh and extreme environments. However, the interaction of nickel and nickel based alloys with water and oxygen atom causes dissolution of metallic atom and diffusion of elements. After then, oxidation arises at the surface. Therefore, the formation of oxide layer is an unavoidable process in high temperature water environments. The oxidation process of nickel based alloys is at the origin of the initiation of stress corrosion cracking(SCC), Stress corrosion cracking is arisen from interaction of mechanical, metallurgical, and electrochemical factors. It can induce failure of structural materials. Hence, it is important to understand and solve stress corrosion cracking in nickel based alloys. Therefore, this study's objective is to understand processes of early stage oxidation through the first principles method and molecular dynamics simulation
[en] The changes in the crystalline forms of the Zirconium oxide show different mechanical properties and corrosion resistance. Therefore, the investigation of oxidation behavior of Zr-alloys in nuclear power plants is necessary to operate the nuclear power plant in safe way. The Raman spectroscopy is the measurement of the inelastic scattered wavelength and intensity from the each molecule. The Raman spectroscopy can identify the oxidation products and oxide films on surface of the metal and alloys by 'in-siu' investigation. It can give a clear result of oxidation formation as function of time. There are several studies about in-situ method of aqueous corrosion were conducted for metals and alloys at elevated temperature in pure water and LWR environments. Especially, Maslar et. al conducted the in situ Raman spectroscopic investigation for Zirconium-niobium alloy corrosion under hydrothermal condition. The Zr-Nb alloy coupon was exposed to air-saturated water at a pressure of 15.5 MPa and temperatures ranging from 22 ∼ 407 .deg. C. The phase transformation was observed and the different corrosion product was observed before and after ZrO2 film formation. In this study, the in-situ Raman Spectroscopy has been applied in order to analyze the oxidation behavior and phase transformation of the surface film on zirconium alloys which is used as cladding materials of fuel rod in primary water conditions of pressurized water reactors
[en] The intermediate level liquid radwastes (ILLW) will be generated during Mo-99 production at KIJANG research reactor which is planning by KAERI. Currently, the KIJANG research reactor is on the construction regulation phase, and it require ILLW storage capability at least 20 years. All radwastes treatment processes of KIJANG research reactor should be certified, and all treated radwastes can shift to final disposal site. Furthermore, the treatment processes have to fit for the radwastes from the research reactor because, the radwastes of research reactor differ from that of nuclear power plants. In this study, we developed the treatment method for ILLW, and evaluated the disposability. 4.1 Cementation is a certified technology, and the activity of solidification is 3.01E+06 Bg/g. The operation range is 0.40 ⁓ 0.60 of w/c ratio, and the salts contents are 6.83 ⁓ 10.25wt.%. 4.3 Optimum condition is 0.50 ⁓ 0.55 of w/c ratio, and the physical and chemical properties of cementation meet the acceptance criteria of Gyeongju disposal site
[en] Test results of high burnup fuel behavior under RIA(reactivity insertion accident) indicated that fuel might fail at the fuel enthalpy lower than that in the current fuel failure criteria was derived by the conservative assumptions and analysis of fuel failure mechanisms, and applied to the analysis of control rod ejection accident in the 1,000 MWe Korea standard PWR. Except that three dimensional core analysis was performed instead of conventional zero dimensional analysis, all the other conservative assumptions were kept. Analysis results showed that less than on percent of the fuel rods in the core has failed which was much less than the conventional fuel failure fraction, 9.8 %, even though a newly derived fuel failure criteria -Fuel failure occurs at the power level lower than that in the current fuel failure criteria. - was applied, since transient fuel rod power level was significantly decreased by analyzing the transient fuel rod power level was significantly decreased by analyzing the transient core three dimensionally. Therefore, it can be said that results of the radiological consequence analysis for the control rod ejection accident in the FSAR where fuel failure fraction was assumed 9.8 % is still bounding. 18 tabs., 48 figs., 39 refs. (Author)
[en] A Pressurized Thermogravimetric Analyser (PTGA) was used to determine the reactivity of coal char using isothermal techniques, at elevated pressure. Coal chars were prepared in a pressurized drop tube furnace (PTGA) at a high heating rate. The effects of reaction temperature and partial pressure on reaction rate of the coal char with carbon dioxide were tested with the ranges of 800 ∼ 1000 .deg. C and 0.1∼ 0.5 MPa, respectively. It was found that the reaction rate was dependent on the partial pressure. Kinetic parameters of reaction rate was determined for several coal chars with the nth order reaction model
[en] Decommissioning information in the various fields (decommissioning legal regulatory requirements, facility characteristics information, radiation / performance information, radioactive waste management, radiation protection, etc.) related to decommissioning is generated during decommissioning for nuclear facilities, from permanent shutdown to site restoration. Since a vast amount of information is generated and this information is used for important factors such as waste management and cost estimation, it is necessary to manage information systematically and accurately. Various management systems have been developed so far, but they are used and managed independently as various systems, which limits the complexity and information management. In order to overcome this problem, we intend to develop an integrated management system by securing the connection between existing program unit information in the current research. In this study, main process functions are implemented to efficiently manage the necessary information in the decommissioning process of nuclear facilities based on existing conceptual design and framework design. In order to systematically and accurately manage related information generated during decommissioning of nuclear facilities, we have developed a methodology for estimating decommissioning costs based on the results of existing framework design phases. In addition, it can be applied to various types of nuclear facilities by connecting facility characteristics information and decommissioning cost evaluation function based on database which can easily utilize and expand information with the aim of implementing the functions necessary to calculate decommissioning waste quantity and basic decommissioning cost calculation.