Bum-Kyoung Seo

Removal of Radioactive Cesium Using Prussian Blue Magnetic Nanoparticles

Radioactive cesium (137Cs) has inevitably become a human concern due to exposure from nuclear power plants and nuclear accident releases. Many efforts have been focused on removing cesium and the remediation of the contaminated environment. In this study, we elucidated the ability of Prussian blue-coated magnetic nanoparticles to eliminate cesium from radioactive contaminated waste. Thus, the obtained Prussian blue-coated magnetic nanoparticles were then characterized and examined for their physical and radioactive cesium adsorption properties. This Prussian blue-coated magnetic nanoparticle-based cesium magnetic sorbent can offer great potential for use in in situ remediation.

Removal of cesium ions from clays by cationic surfactant intercalation

We propose a new approach to remediate cesium-contaminated clays based on intercalation of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) into clay interlayers. Intercalation of DTAB was found to occur very rapidly and involved exchanging interlayer cations. The reaction yielded efficient cesium desorption (∼97%), including of a large amount of otherwise non-desorbable cesium ions by cation exchange with ammonium ions. In addition, the intercalation of DTAB afforded an expansion of the interlayers, and an enhanced desorption of Cs by cation exchange with ammonium ions even at low concentrations of DTAB. Finally, the residual intercalated surfactants were easily removed by a decomposition reaction with hydrogen peroxide in the presence of Cu2+/Fe2+ catalysts.

The preliminary 3D dynamic simulation on the RSR dismantling process of the KRR-1&2

Abstract A three-dimensional graphic simulation has been carried out for the dismantling process of the Rotary Specimen Rack(RSR) in the Korea Research Reactor-1&2 (KRR-1&2). First of all, the general steps of the graphic simulation were established and reviewed for the dismantling process of the object. Four dismantling processes, which are the removal of RSR, reactor core region, beam tube, and thermal column and activated concrete, were selected for the graphic simulation on the virtual space by the consideration of the activation, worker training, work difficulty and so on. In the present study, the dismantling procedure of the RSR was divided into several steps and its visual simulation was performed by the 3D graphic software. Finally, the simulation result was converted to moving file with extension of AVI so that easy approach can be made on window OS system.

Development of the In-situ Monitoring System for Pipe Internal Contamination Measurement in the Decommissioning Site

The in-situ monitoring system of pipe internal (IMSPI) was developed for transporting a variety of survey tools into pipes. Tools available for use with the system include alpha, beta and gamma-ray detectors and video cameras. In the IMSPI, phoswich detector for simultaneous measurement of alpha- and beta-particles and CdTe detector for gamma-rays were used. The phoswich detector composed with ZnS(Ag) and plastic dual scintillator was manufactured, which could be applicable in the contamination monitoring systems. The IMSPI used a helical gear and automatic controller to transport radiation detectors and video cameras into pipes. And the membrane inserted into a pipe to transfer the characterization tools through the piping, providing a clean conduit through which the detectors and camera could travel.

Preparation and characterization of a double-layered porous film to assay for surface radioactive contamination

Abstract Double-layered polysulfone (PSF) membranes, containing cerium activated yttrium silicate (CAYS) as a fluor, were prepared from double casting of two polymeric solutions, and their morphology and radioactive capacity were compared with those of single-layered membranes. The backing, the bottom layer of double-layered membranes, was made of a binary casting solution of polysulfone and methylene chloride (MC), its cast film being solidified by vacuum evaporation. The second casting solution with dimethylformamide (DMF) as solvent was cast over the solidified backing film and coagulated by being immersed into a nonsolvent bath of water or methanol. The prepared membranes revealed two distinct, but tightly attached, double layers, their attachment being identified by the morphology of the interface between the two layers. Membranes prepared with CAYS in the casting solution have more developed macropores than those prepared without CAYS. In the radionuclide detection test of the CAYS-impregnated membranes, the membranes solidified by water precipitation showed better detection efficiency than those solidified by methanol precipitation. Its superior efficiency is not due to better holding of the radioisotopes, but due to greater density of CAYS in the membrane surface region. In the comparison with single-layered membranes, the double-layered membranes showed a greater ability in holding the radionuclides, spotted on the surface, as well as an improvement in physical strength because of the dense backing layer.

Development of the Sampling and Nuclide Analysis Methods for Spent HEPA Filter Wastes

Spent filter wastes of about 2,160 units have been stored in the waste storage facility of the Korea Atomic Energy Research Institute since its operation. These spent filters have generally consisted of a HEPA filter after its filtering of all the contaminants in the gas stream generated during the operation of the HANARO research reactor and the nuclear fuel cycle facilities. At the moment, to secure enough storage space, it is necessary to make a volume reduction of the stored radioactive wastes through a compression treatment or a regulatory clearance. There have been many studies on a treatment and a clearance of the low level radioactive wastes generated from nuclear facilities. These methods are used in view of a reduction of a management cost and disposal cost and the security of free space for a waste storage facility approaching saturation. In order to dispose of the spent filters, it is first necessary to conduct a radionuclide assessment of them. To do that, a sampling procedure should be prepared to obtain a representative sample from a spent filter. As for conducting a nuclide analysis for this representative sample, a corresponding spent filter can be determined as either a regulatory clearance waste or a radioactive waste.Copyright

Preparation Methods of Copper-Ferrocyanide Functionalized Magnetic Nanoparticles for Selective Removal of Cesium in Aqueous Solution

Copper ferrocyanide functionalized magnetite nanoparticles (Cu-FC-MNPs) were successfully synthesized by the immobilization of copper and ferrocyanide on the surface of [1-(2 amino-ethyl)-3-aminopropyl] trimethoxysilane modified magnetite nanoparticles. A radioactive cesium (Cs) adsorption test was carried out to investigate the effectiveness of Cu-FC-MNPS for the removal of radioactive Cs. Furthermore, the Cu-FC-MNPs showed excellent separation ability by an external magnet in an aqueous solution.Copyright

Radioactive Analysis of a Spent HEPA Filter Using the Distribution Characteristics of the Captured Radionuclide

To investigate the species and the distribution of the captured nuclides in a HEPA filter, it was dismantled into a metal part and a filter medium part to obtain a filter medium. From the nuclide analysis results for a filter medium part through pre-treatment of it, it was possible to obtain three kinds of typical distributions in view of the distribution of the captured nuclides in the filter medium. When considering these distribution characteristics of the captured radionuclide, the region showing the high concentration of the captured nuclides was the intake or the outlet part of the HEPA filter. On the other side, the middle part generally represented a uniform distribution below the average concentration of the captured nuclides. Therefore, in the event of taking a representative sample of a HEPA filter at the intake and the outlet part, the results of a nuclide analysis for that sample could be estimated as existing in the range from 1.0 to 1.5 times the real concentration of the nuclides captured by a filter medium. As a result, to conduct a radionuclide assessment of a spent HEPA filter without a dismantlement of it, the analysis results for a representative sample taken from both the intake and the outlet part of a spent HEPA filter could be regarded as an average value for the corresponding HEPA filter.

The Measurement of Radioactive Surface Contamination Using an Inorganic Fluor-Impregnated Membrane

Solid scintillation proximity membranes were prepared for measuring surface in laboratories contaminated by the all types of radionuclides, such as H-3, C-14, and Cs-137 etc. Polysulfone scintillation proximity membranes were prepared by impregnating Cerium Activated Yttrium Silicate (CAYS),an inorganic fluor, in a membrane structure. The inorganic fluor-impregnated membranes were applied to detect the radioactive surface contamination directly without the aid of a scintillation cocktail. The preparation of membranes was divided into two processes. A supporting polymer film was made of casting solution consisting of polysulfone and solvent, their cast film being solidified by vacuum evaporation. CAYS-dispersed polymer solutions were cast over the first, solidified polymer films and coagulated either by evaporating solvent in the solution with non-solvent in a coagulation bath. The prepared membranes had two distinguished, but tightly attached, double layers: one is the supporting layer of dense polymer film and the other results revealed that the prepared membranes were eficient to monitor radioactive contamination with reliable counting ability. For enhancement of pick-up and measurement efficiency, the membrane was prepared with the condition of different membrane solidification. The scintillation produced by interaction with radiation and CAYS was measured with photomultiplier tube. The test results of the cocktail-free wipe test showed that the prepared membranes were efficient to monitor radionuclide-contaminated areas with the good counting ability as well as with the decrease of overall production of radioactive waste.Copyright