The radiolytic decomposition of oxalic acid was investigated using gamma irradiation for decontamination of nuclear power systems. The study used high-purity analytical grade chemicals, with initial concentrations of oxalic acid prepared at 1, 2, 5, and 10 mM, and the initial pH was adjusted to 2-3 at each test condition. Gamma irradiation was performed using a high-level Co-60 source, and absorbed doses were 5, 10, 20, 30, and 50 kGy. The results showed that the efficiency of gamma irradiation decreased with longer gamma exposure time, and the G-value increased with the initial concentration of oxalic acid. Interestingly, the G-value decreased with accumulated radiation dose, but the removal increased. The dose constant ranged from 0.1695 to 0.0536 kGy-1 at different initial concentrations, and the G-value was inversely proportional to the dose constant. The study concluded that oxalic acid was successfully degraded by gamma irradiation, and 92% removal was obtained at the initial concentration of 10 mM. The mineralization of oxalic acid at higher concentrations was more difficult due to the great number of generated intermediates.

Organic scintillator is easy to manufacture a large size and the fluorescence decay time is short. However, it is not suitable for gamma measurement because it is composed of a low atomic number material. Organic scintillation detectors are widely used to check the presence or absence of radiation. The fluorescence of organic scintillators is produced by transitions between the energy levels of single molecules. In this study, an organic scintillator development study was conducted for use in gamma measurement, alternative materials for secondary solute used in basic organic scintillators were investigated, and the availability of alternative materials, detection characteristics, and neutron/gamma identification tests were performed. In other words, a secondary solute showing an improved energy transfer rate than the existing material was reported, and the performance was evaluated. 7-Diethylamino -4-methylcoumarin (DMC), selected as an alternative material, is a benzopyrone derivative in the form of colorless crystals, has high fluorescence and high quantum yield in the visible region, and has excellent light stability. In addition, it has a large Stokes shift characteristic, and solubility in solvent is good. Through this study, it was analyzed that the absorption wavelength range of DMC coincided with the emission wavelength range of PPO, which is the primary solute. Through this study, it was confirmed that the optimal concentration of DMC was 0.04wt%. As a result of performing gamma and neutron measurement tests using a DMC-based liquid scintillator, it showed good performance (FOM=1.42) compared to a commercial liquid scintillator. Therefore, the possibility of use as a secondary solute was demonstrated. Based on this, if studies on changes in the composition of secondary solute or the use of nanoparticles are conducted, it will be possible to manufacture and utilize a scintillator with improved efficiency compared to the existing scintillator.

The safe, efficient and cost-effective decommissioning and dismantling of radioactive facilities requires the accurate characterization of the radionuclide activities and dose rate environment. And it is critical across many nuclear industries to identify and locate sources of radiation accurately and quickly. One of the more challenging aspects of dealing with radiation is that you cannot see it directly, which can result in potential exposure when working in those environments. Generally, semiconductor detectors have better energy resolution than scintillation detectors, but the maximum achievable count rates are limited by long pulse signals. Whereas some high pure germanium detectors have been developed to operate at high count rates, and these HPGe detectors could obtain gamma-ray spectra at high count rates exceeding 1 Mcps. However, HPGe detectors require cooling devices to reduce the leak currents, which becomes disadvantageous when developing portable radiation detectors. Furthermore, chemicalcompound semiconductor detectors made of cadmium telluride and cadmium zinc telluride are popular, because they have good energy resolution and are available at room temperature. However, CdTe and CZT detectors develop irradiation-induced defects under intense gamma-ray fields. In this Review, we start with the fundamentals of gamma rays detection and review the recent developments in scintillators gamma-ray detectors. The key factors affecting the detector performance are summarized. We also give an outlook on the field, with emphasis on the challenges to be overcome.

Heavy metal ion separation of commercial polymeric membranes is investigated to elucidate the permeation mechanism and possibility on applying treatment of wastewater from various origins. Since wastewater contains significant amount of heavy metal ions, their treatment to recycle or reuse is necessary. Polyamide based commercial membranes are prepared to test their separation performance on single- & multi-component heavy metal aqueous solutions. This study indicates that polymeric membranes can be potential candidate for heavy metal separation.