Gwang Min Sun

Comparison of elemental contents of Korean space foods using instrumental neutron activation analysis

The analysis of mineral contents in space foods is needed to obtain an information on a comprehensive elemental composition as well as the investigation on the effects of human nutrition and health based on the dietary intake of mineral elements. Recently, six items of new Korean space foods (KSFs) such as kimchi, bibimbap, bulgogi, a ramen, a mulberry beverage and a fruit punch which was developed by the KAERI, and the contents of more than 15 elements in the samples were examined by using instrumental neutron activation analysis (INAA). Five biological certified reference materials, NIST SRM were used for analytical quality control. The results were compared with those of common Korean foods reported, and these results will be applied toward the identification of irradiated foods.

The geographical origin and chemical composition in phellinus mushrooms measured by instrumental neutron activation analysis

In order to expand the utilization of phellinus mushrooms as a dietary supplement, we attempted to evaluate the chemical composition by measuring its inorganic elemental content with the aid of instrumental neutron activation analysis (INAA). Twenty seven phellinus mushrooms samples were collected from Korea, Cambodia, and Vietnam. A total of 28 elements were analyzed in the phellinus mushroom samples using the INAA. The concentrations of Ca, K, and Mg are much higher than those of other elements in phellinus mushroom samples. The sum of determined elemental concentration in Cambodia samples was about 2–6 times higher than those in Korea and Vietnam samples, respectively. Based on our measurement data, we attempted to discriminate the geographical origin using principal components analysis (PCA) and linear discriminant analysis (LDA). The geogrpahical origins of all samples were clearly classified with correct classification rate of 100%.

Monte Carlo ray-tracing simulations for cold neutron beam guides of CONAS

The cold neutron guides dedicated to the cold neutron activation station (CONAS) at HANARO (KAERI, Republic of Korea) offering a substantial improvement of analytical sensitivity were simulated by using two Monte Carlo neutron ray-tracing packages (McStas and VITESS). In this paper, the estimations of neutron intensities and fluxes were calculated at some particular positions of the two cold neutron guides, namely CG1 and CG2B. In addition, some drawbacks of the simulation with the energy spread of the incident beams were found out based on the comparison between the simulation and experimental results.

Optimization of HANARO cold neutron induced prompt gamma activation analysis system by using Monte Carlo code

Prompt gamma activation analysis (PGAA) is a nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. The principle of PGAA technique is based on detection of captured gamma-ray emitted from an analytical sample while being irradiated with neutrons. Use of a cold neutron beam guide greatly reduces the gamma-ray background at the analytical sample while maintaining a neutron capture rate is comparable to that of standard thermal neutron PGAA. A new cold neutron induced prompt gamma activation analysis (CN-PGAA) system has been under construction since April of 2009 at the HANARO Cold Neutron Building (KAERI, Republic of KOREA). In this study, the Compton suppression factor of the CN-PGAA system was estimated to be 5.5 using a 60Co radioactive source in conjunction with the MCNPX simulations. Several parameters of the CN-PGAA system were studied to estimate and optimize the performance of the system: scintillation material in the guarded detector of a Compton suppression spectrometer (CSS); the relative positions of the HPGe detector and annular detector; and the distance between the HPGe detector and back catcher BGO detectors of the CSS. In addition, the neutron ray-trace simulation package, McStas, was adopted to predict the neutron flux and wavelength distribution at the end of the cold neutron beam guide. These results served as input for the MCNPX simulation of the CN-PGAA system.

Enhancing neutron spectral results based on the combination of genetic algorithm and activation method

AbstractThe generated neutron spectrum from KIRAMS MC-50 cyclotron has been adjusted and enhanced by the combination of the genetic algorithm (GA) and activation foil methods. The activation rates were derived from the measurements of Shieldwerx activation foil using the ORTEC HPGe spectroscopy system and applying the GA method to return the adjusted spectral information. It is worth mentioning here that the result, which was successfully validated with the unfolding spectrum from STAY’SL PNNL code, is significant as it will be a referenced neutron spectrum for the experiments of the MC-50 cyclotron.

A Preliminary Study of Korean Geostansdards Using Mesozoic Granites

In this study, we selected three representative granite samples and conducted petrological observation to establish the Korean geostandards. Samples were taken from the two Jurassic (KJG-1, KJG-2) and one Cretaceous (KCG1) granites in South Korea. The powder samples were prepared by the standard pulverization process, and glass beads were made for geochemical analysis using X-ray fluorescence (XRF) method, and finally, major element contents of the samples were acquired. The analytical data are shown with mean, standard deviation and relative standard deviation. The accuracy of the analysis was confirmed within an estimated error range of about 5% by comparing the recommended true values of the USGS and GSJ geostandards. Also, we checked the analytical precision by calculating a relative standard deviation of about 3% from the XRF analytical results for the three samples.

Development of a single photon counting gamma-ray camera for Compton noise elimination

In this study, the noise resulting from Compton scattering was quantified when gamma images were acquired with a 50-mm thick scintillator array detectors, and the solution method was proposed to its elimination. To perform it, a system capable of recording the events and occurrence times at each one of the 144 scintillator array elements has been developed. This study also presents that the Compton noise was not the dominant source of image quality degradation in the experiment, but its negative influence of the Monte Carlo simulation can increase greatly to lower detection threshold energies.

Quantification of Nb and Zr in the irradiated pressure tubes from Wolsong CANDU Unit 1 by neutron activation analysis

When the Wolsong 1st CANDU reactor in Korea is reaching the end of its original lifespan, decommissioning has been one of the largest issues faced by the nuclear industry and the government for the estimation of expense. The radioactive sources in the construction stuffs and components of the reactor such as pressure tubes, steam generators must be evaluated for the estimation of the appropriate expense for the decommissioning. Unfortunately we do not have exact information about the initial composition of the pressure tubes. In this study the elemental contents of Nb and Zr in the activated zircaloy pressure tubes was investigated. Nb is one of the important elements that characterize the physical and mechanical properties of the pressure tube and a major source of high radioactivity. The prepared samples were strongly irradiated again in the vertical irradiation channel at the HANARO research reactor in the Korea Atomic Energy Research Institute (KAERI) and then measured by an HPGe detector.