[en] Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe₂O₃·nH₂O, n=1-3) and HMO (MnO₂) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO₆ (MnO₆) octahedra with Pb(single_bond)O distance of 2.25-2.35 Angstroms and Pb(single_bond)Fe(Mn) distances of 3.29-3.36 (3.65-3.76) Angstroms. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8x10^-3 to 1.5x10^-2, loading 2.03x10^-4 to 9.1 x 10^-3 mol Pb/g, and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake (∼77%) followed by a slow intraparticle diffusion step (∼23%) resulting in a surface diffusivity of 2.5x10^-15 cm²/s. Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction

[en] Vitrification technology is emerging as one of the most promising options for the treatment of intermediate and low level radioactive waste because of its high volume reduction ratio and long-term excellent characteristics of final waste form in the disposal environment. Korea Electric Power Corporation(KEPCO) had been developed a combined vitrification process composed of a Cold Crucible Induction Melter, a Plasma Torch System and and Off-gas Treatment System, and constructed a vitrification plant. The off-gas treatment system should be designed for the optimal treatment of off-gas depending on the its chemical and radiological characteristics. A computer code for the simulation of off-gas treatment system has been developed in this study. The function and operation parameters for each component of the system were considered. The results calculated using the code were compared with experimental data obtained from orientation tests performed in SGN and design data given by HDPIC. The comparison showed that this simulation code can be used for the optimization of off-gas treatment system in the vitrification plant

[en] Incombustible radioactive waste from nuclear power plants is generally composed of concrete, glass, asbestos, metal, sand, soil, and spent filter. The melting tests for concrete, glass, sand, and spent filter were carried out using 60 kW plasma torch system. Surrogate waste was prepared for the tests and stable cesium was added to the surrogate in order to simulate the radioactive waste. Eleven kinds of surrogate were prepared by mixing the wastes and were melted with the plasma torch system to produce slag samples. The intactness evaluation of the samples was performed to find the optimum mixing ratio of the wastes for the plasma torch melting. The items of the evaluation have included volume reduction factor, visual inspection, cesium trapping efficiency and leaching index. As a result, it was found that the mixing ratio of 3:1 of concrete and glass was the optimum composition considering disposal stability and economical efficiency of the wastes

[en] Plasma technology was first developed in the 19th century and has been extensively applied to various fields of industry such as metallurgy and chemical industry. In 1980s increase in environmental concerns and disposal cost took an important role in applying the plasma torch to treatment of hazardous waste. At the end of 1990, KHNP launched a vitrification research program for treatment of low-level radioactive waste with a view to reduction of waste volume and enhancement of its disposal integrity. A first phase of the research led to the conclusion that 'combined process' which is to treat combustibles with cold crucible melter(CCM) and noncombustibles with plasma melter would be appropriate in economic and technological point of view. Thereafter, CCM technology was successfully developed and the first CCM is under construction in Ulchin Nuclear power site and expected to operate in 2008. As for development of noncombustible radioactive waste treatment, a 200kW plasma torch melter was built at KHNP and series of pilot tests have been performed. Based on the pilot tests, a commercial-scale 500kW plasma torch has been decided to be installed in order to enhance reliability of design data, and help licensing. This paper describes major findings of the KHNP's pilot tests, recent status of plasma melting technology development and core technologies for its commercial application

[en] When Boraflex is subjected to a gamma radiation in the pool aqueous environment, Boraflex is known to undergo changes and the polymer matrix is transformed into silica and silica dominated material. In a typical spent fuel pool the irradiated Boraflex turned out to be a significant source of silica and spent fuel storage racks were needed to be reanalyzed due to Boraflex degradation and the potential loss of boron carbide. In this study, the major factors to service life of Boraflex were analyzed to result in the cumulative radiation dose, chemical properties of coolant, coolant temperature, thickness of Boraflex, storage rack design, B₄C and other material composition of Boraflex, etc. Boraflex degradation analysis was carried out using RACKLIFE. Resultant cumulative radiation dose to Boraflex panel was evaluated at 0.25x10¹⁰rads and subsequent B₄C loss at 1%. However, it was estimated that B₄C loss does not have significant effect on subcriticality to spent fuel storage rack. The operation of spent fuel storage should be optimized by decreasing temperature and circulation rate of coolant. The performance of Boraflex should be improved by optimal shuffling of discharged fuel with computer code in order to reduce the cumulative dose to Boraflex panel, as well

[en] A simulated mixed Dry Active Waste(DAW) has been vitrified using a pilot scale Cold Crucible Melter(CCM). A processability, characteristics of the combustion and dust generation of the DAW in the CCM, and glass properties were investigated and evaluated. The glass melt was maintained at around 1,150 .deg. C constantly and the mixed DAW was fed into the CCM at the feed rate of 10, 15 and 20kg/h during the test. The viscosities of the base and the final glass were well within the desired range. There was electrical conductivity difference between the base glass and the final glass and it was also within the desired range, as 0.33 S/cm. A stable combustion process of the DAW was performed during the test. And only 3.03% of the dust was generated from the cold crucible melter. All regulated emission gases in the stack were well below the environmental regulation limits. The physical properties and chemical durability of the waste glass were satisfactory the required quality

[en] The usefulness of vitrification technology of low and intermediate level radioactive wastes was demonstrated due to volume reduction and mechanical and chemical stability of final waste forms. Therefore economic assessment that is considering by the economic propriety and predicted cost is needed at the preliminary of facility operation. Economic assessment of vitrification facility that is expected to construct in Ulchin 5 and 6 is established. In this study, characteristics and yearly generation of radioactive wastes are based on Ulchin 5 and 6 PSAR. The present worth analysis is worked through the cost-benefit when the vitrification facility will be installed. In conclusion, it would be good choices if it treats radioactive wastes from more than 4 nuclear power plants

[en] Correlations between the amount of DAW (Dry Active Waste) generated from present Korean PWRs and their operating parameters were analyzed. As the result of multi-variable linear regressions, a model predicting the volume of DAW using the number of shutdowns (f_FS) and total personnel exposure (P_E) was derived. Considering one standard error bound, the model could successfully simulate about 85% of the real data. In order to predict the amount of DAW to be generated from a KNGR, another model was derived by taking into account the additional volume reduction by supercompaction system. In addition, the volume of WAW (Wet Active Waste) to be generated from KNGR (Korean Next Generation Reactor) was calculated by considering conceptual design data and replacement effect of radwaste evaporator with selective ion exchangers. Finally, total volume of SRW (Solid Radioactive Waste) to be generated from KNGR was predicted by inserting design goal values of f_FS and P_E into the model. The result showed that the expected amount of SRW to be generated from KNGR would be in the range of 33 - 44 m³y^-1. It was proved that the value would meet the operational target of KNGR proposed by KEPCO, that is, 50 m³y^-1. (author)

[en] Based on the experimental experiences and test data collected through the pilot vitrification plant which has been in operation since October, 1999 and the nuclearization requirements on the plant, KHNP established a plan for building a vitrification facility for the processing of low-and intermediate-level radioactive wastes to be produced in Ulchin Nuclear Power Plants (hereinafter called ^UVF⁾. MOBIS, as the prime contractor for design/engineering, procurement, construction, and start-up of the UVF, has performed the project works with the collaboration of SGN and HEC since the end of 2003 and completed the Basic and Detailed design works by the middle of April, 2005. According to the UVF project milestone schedule, the UVF shall be completed by the end of July, 2007. To meet this project requirement, MOBIS is now preparing the procurement of the equipment and waiting for the license for the installation a d construction of UVF

[en] The idea of using vitrification technologies to process low and intermediate level waste was considered by SGN and KHNP/NETEC (Korea Hydro and Nuclear Power Co., Ltd/ Nuclear Environment Technology Institute) in 1995. The Cold Crucible Melter (CCM) technology has been developed by CEA, AREVA/COGEMA and AREVA/SGN to further increase the performance of vitrification facilities since the beginning of the 1980s. A joint NETEC-AREVA/COGEMA/SGN-CEA- MOBIS program was launched in 1997 to develop the industrial application of the CCM for the incineration/ vitrification of waste produced in the Korean Nuclear Power Plants. The second step of the joint collaboration, completed in October 1999, was devoted to the design and construction of an industrial pilot plant in Daejeon. This pilot facility has been in operation since October 1999. After the completion of the development program, KHNP has decided to implement the process on one of its NPP site:Ulchin in South Korea. A commercial facility is being constructed. This unit will process the wastes produced by the Ulchin 3, 4, 5 and 6 Nuclear Power Plants. The basic design of the facility has been completed by SGN and HD MOBIS. The detailed design is in progress. The main features of the design are presented in the paper