• Journal of the Korean Ceramic Society
• /
• v.43 no.12 s.295
• /
• pp.833-838
• /
• 2006

Graphite is suitable for high temperature structural materials because of chemical stability as well as unique crystal structure. Especially, graphite can be used as a part of a nuclear reactor due to high tolerance at the extreme conditions of high temperature and neutron irradiations. Although study of oxidation properties or behaviors of graphite are very important and essential for the life and stability of the nuclear reactor, most of studies treat this theme lightly. This work focuses on the oxidation characteristics of several grade isotropic graphite of the nuclear reactor.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.5
• /
• pp.450-455
• /
• 1990

Fifty eight obsidian artifacts and four obsidian source samples have been analyzed by instrumental neutron activation analysis. Artifact samples have been classified into classes by unsupervised learning techniques such as eigenvector projection and nonlinear mapping. The source samples have thereafter been connected to the classes by the supervised learning techniques such as SLDA and SIMCA so as to characterize each class by possible source sites. Some difference attributable to different nonlinear mapping techniques and the elemental effects on the separation between classes have been discussed.

• Nuclear Engineering and Technology
• /
• v.53 no.10
• /
• pp.3158-3163
• /
• 2021

Chromium material is commonly used for fusion plasma facing applications because of the low neutron activation property. The Monte Carlo method is one of the useful ways to investigate the ion-target interactions. In this study, Chromium target irradiated by protons was investigated using Monte Carlo based simulation tools. In this context, the calculations of radiation damage on Chromium material irradiated with protons at 17.9 and 22.3 MeV energies were carried out using GEANT4 and SRIM codes. Besides, the cross sections for proton interaction with Chromium target were calculated by the TALYS 1.9 code using CTM + FGM, BSFGM, and GSFM level densities. As a result, GEANT4, SRIM and TALYS 1.9 codes provide a suitable tool for the predictions of radiation damage and cross cross section with proton irradiation.

• Nuclear Engineering and Technology
• /
• v.51 no.3
• /
• pp.784-791
• /
• 2019

In the present study, a series of tungsten austenitic stainless steel alloys have been developed by interchanging the molybdenum in standard SS316 by tungsten. This was done to minimize the long-life residual activation occurred in molybdenum and nickel after decommissioning of the power plant. The microstructure and mechanical properties of the prepared alloys are determined. For the sake of increasing multifunction property of such series of tungsten-based austenitic stainless steel alloys, gamma shielding properties were studied experimentally by means of NaI(Tl) detector and theoretically calculated by using the XCOM program. Moreover, fast neutrons macroscopic removal cross-section been calculated. The obtained combined mechanical, structural and shielding properties indicated that the modified austenitic stainless steel sample containing 1.79% tungsten and 0.64% molybdenum has preferable properties among all other investigated samples in comparison with the standard SS316. These properties nominate this new composition in several nuclear application domains such as, nuclear shielding domain.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.4
• /
• pp.241-246
• /
• 1985

Twenty trace elements were determined in 250 Korean potsherds and 5 clay samples by instrumental NAA. In the absence of identified samples of known origin, the potsherds were classified by a hierarchical centroid sorting method to construct a dendrogram. From this dendrogram 61 well-defined samples were selected to form 8 subclasses and five elements such as Cr, Cs, Sm, Sc and Th were supposed to be the main contributors for the classification. The 61 samples along with 5 clay samples were reclassified by means of minimal spanning tree as well as the hierarchical centroid sorting method by using 5 elements selected. As the results, the potsherds of certain classes defined in this work could be taken as a basis for latter identification and served as batches of identified species.

• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2489-2497
• /
• 2023

Co and Eu impurities in the SSCs are nuclides that dominantly influence the neutron-induced radioactive inventory in metal and concrete radwastes (radioactive wastes) during NPP decommission. The impurity concentrations provided by NUREG/CR-3474 were used for the practical range of Co and Eu impurity concentrations to be applied to the code calculations. Metal structures near the core were evaluated to be ILW (intermediate-level waste) for the whole range of Co impurity concentration, so the boundary line between ILW and LLW (low-level waste) has no change for the whole concentration range provided by NUREG/CR-3474. Also, the boundary line between VLLW (very low-level waste) and CW (clearance waste) in the concrete shield could alter a little depending on the Eu impurity concentration within the range provided by NUREG/CR-3474. From this work, it is found that the concentration of material impurities of SSCs gives no critical impact on determining radwaste levels.

• Journal of the Korean Chemical Society
• /
• v.37 no.11
• /
• pp.961-966
• /
• 1993

The determination of noble metals such as Ir, Au and Ag in the ancient coins has been studied. For the measurement of the activity of $^{192}Ir,\;^{198}Au\;and\;^{110m}Ag$, radiochemical separations including solvent extraction and ion-exchange chromatography were applied to reduce the interference of high energy ${\gamma}$-ray emitted from various radionuclides with long half-life. As a results, $10^{-11}$ g/g level of Ir could be detected and it was found that the three kinds of the detection limits, i.e., critical, detection, quantitative limit, calculated by the method proposed by Currie, were enhanced. Prior to the re-irradiation with neutron, inactive carrier was added in order to determine the recovery yield of Ir in the radiochemical separation. The average recovery yields of Ir, Au and Ag in the 5 coins were 65.3%, 98.5%, 99.5%, respectively.

• Journal of the Korean Chemical Society
• /
• v.15 no.4
• /
• pp.191-197
• /
• 1971

Ruthenium content in highly purified palladium metal (99.9%) was determined by counting $^{105}Rh$ nuclide which was produced by $^{104}Ru(n,{\gamma};{\beta}^-)^{105}Rh$ nuclear reaction. Palladium sample and ruthenium standard were irradiated by neutron with the Pneumatic Transfer System of TRIGA MARK II reactor. Palladium and ruthenium were dissolved by treating with aqua-regia and by fusing with sodium peroxide flux respectively. $^{105}Rh$ was separated through anion and cation exchange resin columns. The ruthenium content was determined by comparing the $^{105}Rh$ activities, obtained from the palladium sample, with that from pure ruthenium standard. The detection limit of ruthenium by the present method is about 1 ppm of ruthenium in 10 mg of palladium, which is approximately 40 times more sensitive than that of the conventional radioactivation method which employs $^{102}Ru(n,{\gamma})^{103}Ru$ nuclear reaction.

• Journal of the Korean Society of Radiology
• /
• v.17 no.1
• /
• pp.17-23
• /
• 2023

In this study, the thermoluminescence kinetics of electron trap in Li₆Y_0.5Gd_0.5(BO₃)₃ (LY_0.5G_0.5BO) scintillator for neutron detection composed of Li, Gd, and B with a high neutron response cross-section were investigated. The thermoluminescence glow curve of the LY_0.5G_0.5BO scintillation single crystal was measured and analyzed using the peak shape method, the initial rise method, and the machine learning algorithm to evaluate the physical parameters of the electron trap. The glow curve of the LY_0.5G_0.5BO scintillation single crystal consisted of a single peak. As a result of analyzing this peak, the activation energy, emission order, and frequency factor of the electron trap were 0.61 eV, 1.1, and 1.7×10⁷ s^-1, respectively. In addition, the possibility of thermoluminescence analysis of scintillators using machine learning was confirmed.

• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.5
• /
• pp.317-324
• /
• 2014

Environmental tobacco smoke (ETS) samples were collected separately in mainstream and side-stream smoke using a self-designed smoking machine, and a total 40 of PM2.5 was collected with low volume air sampler at indoor environments with and without ETS in Daejeon, Korea. About 20 trace elements including toxic metals like As, Cr, Mn, Se, V, and Zn were determined in PM2.5 and ETS samples by instrumental neutron activation analysis (INAA). It is found that the emission factors of K, Cl, Na, and Al were much higher than those of toxic elements for both mainstream and side-stream smoke. The average concentration of PM2.5 was enriched by 1.5 times at smoking area ($58.7{\pm}18.1{\mu}g/m^3$) than at smoking free area ($38.6{\pm}12.7{\mu}g/m^3$). The concentration ratio of each element between smoking and smoking free area were ranged from 1.1 to 6.0 except Cu (1.0); especially, Ce (6.0), La (5.2), K (2.3), and Co (2.0) showed higher ratio, which suggests that the ETS is one of the possible increasing factors of PM2.5 and elemental concentration at indoor environment.