• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.4 no.2
• /
• pp.179-186
• /
• 2006

Chemical wastes are generated from nuclear facilities and R&D laboratories, but the uranium concentration in the final dried cake is evaluated into 11.2 Bq/g, which exceeds the exemption level of 10 Bq/g for each U isotopes, so the cake is categorized into a radioactive waste. Acid dissolution was applied to extract uranium from the waste sludge, and uranium adsorption on the dissolved solution was experimented by using IRN-77 and Diphosil bead. A large amount of resin was required to get above 80% of uranium removal, which was found to be due to a large amount of metal ions simultaneously dissolved from the precipitates with uranium. As an alternative method, acid dissolution is applied to the dewatered wet cake of the sludge, and the natural evaporation method is adopted for the dissolved solution. The uranium concentration of the dissolved solution was estimated to be 6.97E-01 Bq/ml, and the specific activity of the final waste sheets is evaluated to be 4.3 Bq/g. These results lead to the suggestion that the application of acid dissolution to the wet cake and the natural evaporation for the dissolved solution is an effective treatment method for chemical wastes containing uranium.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.4 no.2
• /
• pp.187-195
• /
• 2006

The regulation for the low and intermediate level radioactive waste to be transferred to the disposal facility, recently revised, require that radioactive waste generators should set up waste certification program to verify the radioactive waste conform to the waste acceptance criteria(WAC) before disposal. The radioactive waste disposal facility, scheduled to be constructed in Korea, will institute WAC for the wastes to be transferred to the facility. This WAC is expected to compose of the requirements for the radiological characterization, physical and chemical characterization, physical/chemical restriction, prohibited item, packaging, identification, labeling, and documentation. For the compliance with this regulation, The radioactive waste generators should verify that the waste meet WAC through performance of the waste certification program and are responsible for handing in all the certification documents to the disposal facility. This waste certification program plan was set up as a preliminary program for the certification of radioactive waste generated in Korea Atomic Energy Research Institute (KAERI) and should be further revised until preparation of WAC by disposal agent.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.4
• /
• pp.219-227
• /
• 2009

The effect of organic acids on the adsorption of U(VI) onto oxide surfaces ($TiO_2)$(anatase), $SiO_2$(amorphous) and $Al_2O_3$(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto $TiO_2$ surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto $SiO_2$ surface, however, picolinic acid enhances the adsorption of U(VI) onto $SiO_2$ surface. The latter effect can be understood by considering the formation of a ternary surface complex on $SiO_2$ surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface, In the case of $Al_2O_3$, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the $Al_2O_3$ surface, and an additional spectroscopic study is required.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.4
• /
• pp.213-218
• /
• 2009

Electrowinning process recovers uranium with actinide elements from spent fuels and is a key step in the Pyroprocessing because of proliferation resistance. An analysis of heat transfer of the Electrowinning cell was conducted to develop basic tool for designing engineering-scale Electrowinner. For the calculation of the heat transfer, ANSYS CFX commercial code was adapted. As a result of the calculation, the vertical Heating Zone length had great effect upon temperature of LiCl-KCl eutectic salt. To maintain constant temperature in the salt, the Heating Zone length should be three times longer than the height of the salt. However, the argon and salt temperatures were barely affected by the Cooling Zone length. The temperature under the Cell cover was mainly influenced by the number of the cooling plates. When the cooling plates were installed more than the number of 5, temperature under the cover was maintained below $250^{\circ}C$. These temperature properties had similar tendency toward the temperature of the Cell which was measured from experiments, Simulated heat transfer information from this study could be used to design engineering-scale Electrowinner.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.4
• /
• pp.207-212
• /
• 2009

In this study, a thermal behavior of $PrCl_3$ as one of the lanthanide chlorides in LiCl-KCl molten salts was investigated in an oxidizing condition. First, a thermo-gravimetric analysis (TGA) of $PrCl_3$ was carried out by an injection of $O_2$ gas. Based on the results, an oxidation of $PrCl_3$ in the molten salts was performed by sparging $O_2$ gas with changing temperatures. According to the TGA data of $PrCl_3$, a dissociation of $PrCl_3$ occurred rapidly by about $380^{\circ}C$ and a conversion of $PrCl_3$ to $PrCl_3$ was completed at about $600^{\circ}C$. The thermal behavior of $PrCl_3$ in LiCl-KCl molten salts by sparging $O_2$ gas was similar to that of $PrCl_3$ in the TGA test, and PrOCl as a insoluble compound in the molten salts was precipitated into the bottom of the molten salts. A conversion of $PrCl_3$ to PrOCl in the molten salts occurred actively at a higher temperature than $650^{\circ}C$. And it would be possible to estimate a conversion status of $PrCl_3$ to PrOCl by measuring a $Cl_2$ concentration in a flue gas generated from an oxidation test of $PrCl_3$ in LiCl-KCl molten salts.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.8 no.4
• /
• pp.329-337
• /
• 2010

Radiotracer experiments were performed over two years using pot cultures in a greenhouse to investigate soil-torice seeds transfer factors of radioiodine and technetium for paddy fields around the radioactive-waste disposal site in Gyeongju. Before transplanting rice seedlings, the top about 20 cm soils were thoroughly mixed with $^{125}I$ (2007) and $^{99}Tc$ (2008), and the pots were irrigated to simulate flooded rice fields. Transfer factors were determined as the ratios of the radionuclide concentrations in dry rice seeds (brown rice) to those in dry soils. Transfer factors of radioiodine and technetium were in the ranges of $1.1{\times}10^{-3}{\sim}6.4{\times}10^{-3}$ (three soils) and $5.4{\times}10^{-4}{\sim}2.5{\times}10^{-3}$ (four soils), respectively, for different soils. It seems that the differences in the clay content among soils played a more important role for such variations than those in the organic matter content and pH. As the representative values of radioiodine and technetium transfer factors for rice seeds, $2.9{\times}10^{-3}$ and $1.1{\times}10^{-3}$, respectively, were proposed. In order to obtain more highly representative values in the future, investigations for the sites of interest need to be carried out continuously.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.4
• /
• pp.191-205
• /
• 2009

To characterize the geological features in the study area for high-level radioactive waste disposal research, KAERI (Korea Atomic Energy Research Institute) has been performing several geological investigations such as geophysical surveys and borehole drillings since 1997. Especially, the KURT (KAERI Underground Research Tunnel) constructed to understand the deep geological environments in 2006. Recently, the deep boreholes, which have 500 m depth inside the left research module of the KURT and 1,000 m depth outside the KURT, were drilled to confirm and validate the results from a geological model. The objective of this research was to investigate hydrogeological conditions using a 3-D geological model around the KURT. The geological analysis from the surface and borehole investigations determined four important geologicla elements including subsurface weathered zone, low-angled fractures zone, fracture zones and bedrock for the geological model. In addition, the geometries of these elements were also calculated for the three-dimensional model. The results from 3-D geological model in this study will be beneficial to understand hydrogeological environment in the study area as an important part of high-level radioactive waste disposal technology.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.8 no.4
• /
• pp.293-301
• /
• 2010

Optical fiber cable, as a sensor, was installed on the wall of KAERI(Korea Atomic Energy Research Institute) Underground Research Tunnel(KURT) in order to monitor the physical stability of the tunnel, which was constructed for technical development and demonstration of radioactive waste disposal. This monitoring system has two simultaneous measurements of temperature and strain over time using Brillouin backscatter. According to the results of the monitoring from Jan. 2008 to Nov. 2009, there is no significant displacement or movement at the tunnel wall However, the cumulative volume of total strain increased slightly as time passes with the comparison of the reference observation, which was measured in Jan. 2008. The change in cumulative volume of total strain indicates that the strain level had been affected by saturation and de-saturation phenomena due to groundwater fluctuation at several points at KURT. This system is based on the distributed sensing technique concept, not point sensing. By using this system, a displacement can be detected with the range from $20{\mu}{\varepsilon}$ to $28,000{\mu}{\varepsilon}$ every 1m interval in minimum. A temperature variation can be monitored at every 0.5m interval with the resolution of 0.01 in minimum. Based on the study, this monitoring system is potentially applicable to long term monitoring systems for radioactive waste disposal project as well as other structures and underground openings.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.8 no.4
• /
• pp.279-291
• /
• 2010

To characterize geological features in study area for high-level radioactive waste disposal research, KAERI (Korea Atomic Energy Research Institute) has been performing the several geological investigations such as geophysical surveys and borehole drilling since 1997. Especially, the KURT (KAERI Underground Research Tunnel) constructed to understand the deep geological environments in 2006. Recently, the deep borehole of 500 m depths was drilled to confirm and validate the geological model at the left research module of the KURT. The objective of this research was to identify the geological structures around KURT using the data obtained from the deep borehole investigation. To achieve the purpose, several geological investigations such as geophysical and borehole fracture surveys were carried out simultaneously. As a result, 7 fracture zones were identified in deep borehole located in the KURT. As one of important parts of site characterization on KURT area, the results will be used to revise the geological model of the study area.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.6 no.3
• /
• pp.163-170
• /
• 2008

The reductive stripping of Np using a n-butyraldehyde (NBA) from loaded organic solution containing Np, which was oxidative-extracted in a system of a 30 % TBP/NDD-2M $HNO_3$ and O/A=2 containing 0.005 M $K_2Cr_2O_7$ as an oxidant of Np, was studied. The stripping yields of Np was increased with an increasing the NBA concentration, with a decreasing the nitric acid concentration of stripping solution and with a decreasing the reaction temperature. The apparent reductive stripping rate equation was shown by the following equation : $-d[Np]_{Org.}/dt$ = 1,524 exp(-2,906/T) $[NBA]^{0.91}\;[H^+]^{-0.92}[Np]_{Org.}$. At 1.04 M NBA and 2 M $NHO_3$, the stripping yield of Np and U was 70.1 %, and 7.1 %, respectively, and the separation factor of U over Np ($=D_U/D_{Mp}$) was about 30.4. Therefore, it was found that U and Np co-extracted in a system of TBP-$HNO_3$ could be effectively mutual-separated by the NBA.