[en] Polychlorinated biphenyls (PCBs) were commercially produced from 1920s as complex mixtures containing multiple isomers for a variety of applications. They are very toxic, chemically stable and resist microbial, photochemical, chemical, and thermal degradation. The public, legal, and scientific concerns about PCBs arose from research indicating they were environmental contaminants that had a potential to adversely impact the environment, and, therefore, were undesirable as commercial products. Eventually, most producers reduced or stopped production of PCBs in the 1970s. Stockholm convention on POPs (Persistent Organic Pollutants), which was effective on May 2004 and 151 nations including Korea were joined on June 2005, asked to dispose of PCBs by 2028 with environmental friendly methods. Korean government also has declared to conduct by 2015. According to the Environmental law of Korea, over 2 ppm of PCBs has to be decomposed by legal methods of incineration and thermal destruction. But those are inapplicable owing to the environmental groups. KAERI(Korea Atomic Energy Research Institute) has recently developed a remarkable technology for radiation treatment of toxic chemicals including chlorides using an electron beam accelerator. Electron beam accelerator of 2.5 MeV energy and 100 kW power capacity was used to decompose of PCBs having been used as a commercial transformer oil for more than 30 years. The oil were irradiated with ∼ 0.1 percent of TEA (Triethyl Amin) to make chloride ion aparted off from the PCBs into precipitate at the conditions of normal temperature and pressure. The concentrations of PCBs were measured by GC (Gas Chromatography) with ECD (Electron Capture Detector) following the KS (Korean Standard) test procedure. Electron beam should be a useful tool for environmental conservation. Residual concentrations of PCBs after irradiation were depended on the absorption dose of electron beam energy. Advantages comparing to other methods such as chemical destruction, biodegradation, IR, UV, and so on for decomposition of PCBs in transformer oil are economic, massive, no additive, simple process owing to the normal temperature and pressure operation

[en] The vibratory compaction method has long been considered as a possible alternative to conventional powder pellet route for nuclear fuel fabrication. Despite the predominant adoption of the latter for commercial enterprises, there are interesting features of the former for application especially to remote fabrication of radioactive fuels for proliferation resistance by making advantageous use of its technical simplicity and concomitant cost benefit. For futuristic development of nuclear fuel fabrication, the potential benefits of vibratory compaction alternative may have to be reappraised. An interesting case in such respect can be studied for DUPIC (Direct Use of Spent PWR fuel in CANDU) program at KAERI initiative, which is being undertaken in international cooperation. The DUPIC program is meant to convert spent PWR fuel into CANDU fuel by direct refabrication without any separation of sensitive material. Although the DUPIC program has taken the conventional pellet method as the reference technology, the remote operation and maintenance required for the radioactive processes remain to be a technical challenge. The analysis is a case study for DUPIC fuel fabrication to size up the potential cost benefits of vibratory compaction alternative, but it could be also an example for other studies on fuel fabrication by remote technology. (author)

[en] DUPIC fuel cycle technology is currently under development at KAERI in cooperation with Canada, the USA and the newly joined IAEA. The DUPIC concept is based on the idea that the bulk of spent PWR fuel can be directly refabricated into a reusable fuel for CANDU reactors, of which high efficiency in thermal neutron utilization would burn the fissile remnants in spent PWR fuel. As there is no separation of sensitive materials involved in the direct refabrication, the DUPIC fuel cycle is dubbed proliferation-resistant. The anticipated benefits of the DUPIC fuel cycle are multiple: the removal of spent PWR fuel for reuse in CANDU reactors at doubling burnup, reduces spent CANDU fuel, savings of natural uranium for CANDU fuel, etc. In order for DUPIC fuel to be qualified ultimately as a licensable and proliferation-resistant fuel, the database of the fuel behavior and information on the fabricability, safeguardability, etc. should be established through the developmental phases. The characteristics of the DUPIC fuel cycle technology, together with its development program at KAERI, are described in this paper. (author)

[en] Conceptual design of DUPIC irradiation pellets with double cladding was carried out. And the preliminary study of the temperature effect on the design and manufacturing parameters of DUPIC pellets through HEATING and GENGTC was performed. The analysed results of the newly designed DUPIC pellets to be irradiated in HANARO, were, 1) thermal conductivity of fuel, linear power of fuel and axial gap affected greatly the temperature of fuel, 2) thickness of sheath, gamma heating rate and thermal transfer coefficient affected little the temperature of fuel. 3) the centerline temperature calculated by HEATING was evaluated higher than that by GENGTC such presented to be desirable for using GENGTC in the view point of safety GENGTC, 4) by transient thermal analysis, after 160 seconds, the temperature of fuel reaches its equivalent temperature. (author). 3 tabs., 16 figs

[en] A simulated fuel specimen which was irradiated at the HANARO research reactor up to 3300 MWd/tU of a burn-up at the condition of 36 kW/m of a maximum linear power was studied by a shielded EPMA (Electron Probe Micro-Analyzer). In order to obtain an accurate analysis results, chemical and EPMA analyses were also performed on un-irradiated fresh simulated fuel, the results of which were compared with those of the irradiated simulated fuel. This study concentrated on the metallic precipitates of the irradiated simulated fuel specimen which contained lots of fission products. Among the several properties of the metallic precipitate, its size and composition were investigated. A large metallic inclusion was also observed in the irradiated simulated fuel, from which X-ray photographs were taken to analyze its properties

[en] Design and safety analysis of fuel, mini-element and capsule for DUPIC fuel irradiation at HANARO were carried out. Three mini-elements shall be installed in the irradiation capsule, of which one mini-element shall include 5 pellets, and irradiated simultaneously. Cooling water flows around the mini-elements. Linear power and composition of fuel are the same as those for DUPIC fuel, and OR hole of HANARO is selected for irradiation. Mock-up capsule was fabricated and tested for vibration and pressure drop, and the result of the tests proved to be compatible to HANARO. Analyzing maximum temperature and inner pressure of mini-element showed to be safe during irradiation. Thermal stress of cladding was calculated to be lower than the limit of stress intensity defined in ASME code. Accident analysis of RIA and locked rotor of HANARO showed that fuel is safe. (author). 27 refs., 17 tabs., 40 figs

[en] The present work studied the formation of new phases by adding alloying additions (Ca, Sr, and Ce) in AZ31 alloy at micro-levels (approximately 0.2 wt.% per element). Quantitative electron probe micro-analysis (EPMA) was used to identify the compositions of these phases; a comparison in the morphology and distribution of an identical phase in different alloy systems was made; and the thermodynamic software of FactSage^TM was utilized to calculate the possible intermetallic phases during solidification. The results of EPMA showed the existence of phases other than Mg₁₇(Al, Zn)₁₂ and Al₈Mn₅ in AZ31 alloy, namely: Al₂Ca, Al₂Sr, Al₁₁Ce₃, Al₈CeMn₄, and Al₂(Ca Sr); and these new phases were thermally stable at 450 ^oC for 10 h. The morphology and distribution of second phases in different alloy systems were self-consistent. These phases were well predicted by FactSage^TM with recent light alloy database.