[en] This study was performed for suggesting a simulation method that can create accurate virtual models of objects with free curved surfaces and perform distortion-free MCNPX simulations. The virtual models acquired by using 3D scan equipment with an accuracy of approximately ±0.025 mm in length, compare with actual objects and are comprised of 11104 polygons. Generally, MCNPX simulations of objects with free curved surfaces are performed through voxelization. In this study, polygon model be tetrahedralized by TetGen for the construction of MCNPX geometry to distortion-free. Then, dose estimation was successfully performed after converting the virtual model into an MCNPX input. With this in mind, a voxelized model was constructed for comparison purposes. The dose estimation functions of the two models were found to be similar, showing a similar amount of computing time by using the mesh tally option with 2e7 histories: for the tetrahedralized model, 729.67 minutes; for the voxelized model, 720.11 minutes. (authors)

[en] Neutron source play essential roles in various industrial and scientific fields. In particular, the fast neutron can be used to study of irradiation effect of neutrons on single event upset of semiconductor devices, materials, and bio-sciences. There are several approaches to obtain neutron beams with the desired energy spectrum such as a nuclear research reactor, a neutron-emitting radio isotopes ("2"5"2Cf and Be-couple "2"4"1Am), and a bombarding proton beams on a target. In the bombarding proton beams case, neutron beams are generated mainly through the (p, n) charge exchange reaction. By adjusting the beam energy, the target material and the thickness of the target, the resulting neutron spectrum can be controlled to a certain degree. Beryllium is widely used as the target material because of its high melting point, good thermal conductivity and many other advantaged features. The purpose of present work is to characterize the neutron flux energy spectrum which produced by a beryllium target with 0.5 cm thickness at 35 MeV energy providing by the MC-50 cyclotron of the KIRAMS (KOREA). Neutron spectrum at the irradiation position of the MC-50 cyclotron was measured by using activation method and been unfolded with the both interactive codes as SAND and STAYSL. Measurements made with foil-activation technique provided valuable information about the neutron spectrum in the irradiation position of the MC-50 cyclotron in KIRAMS. The group cross sections of a certain thickness of foil were processed before unfolding. The results of spectrum unfolding are generally consistent

[en] For the mass inspection of attached foils such as printed electrodes, mass should be measured by a non-contact method with the capacity to measure a small mass of micrograms. In this study, the masses of 1 mg to 10 mg electrodes were evaluated using an X-ray microscope. The results were compared with the masses determined by using a digital scale with a 0.005 mg error. The average of the relative error between the mass measurements using the X-ray microscope and those using the digital scale was less than 2.51%. The results show that X-ray mass evaluation method can be used for mass measurement of micro objects by replacing a digital scale.

[en] For the efficient use of the particle beam, characteristics of the particle beam should be analyzed. The characteristics of the beam can be estimated by the neutrons produced during the accelerator operation. In order to understand the physical properties of neutrons including the energy spectrum, spreading directions, and the amount of the neutrons produced while the particle accelerators run, an unfolding process has been employed. An unfolding method combines the neutron activation analysis with the computer simulation. This combined method is accurate than measuring neutrons directly in that the initial estimation is obtained by the computer simulation and further corrected by the measurement data. This simulation-activation measurement combined unfolding technique, however, is highly dependent on simulation without sufficient number of the activation samples. Available materials for activation foil are limited. Therefore, in this study, a method to acquire additional activation reactions introducing cover materials was studied. The uses of the particle accelerators are rapidly increasing in these days. The produced neutrons should be identified for effective utilization of the facility. The purpose of this study was to suggest foil cover materials to acquire additional activation reactions. Unfolding neutron spectrum was performed with gold and cobalt as activation foils and boron and cadmium as foil cover materials. The unfolded spectrum became similar to actual spectrum according to increasing the number of reactions that were obtained by cover materials with same foils. This study is expected to improve efficiency of neutron spectrum unfolding using limited number of activation foils

[en] In the present study, a new prompt-gamma activation imaging system was proposed for two-dimensional (2D) elemental distributions. The system, as based on coincidence measurement, consists of a high-purity germanium detector for the measurement of the prompt-gamma energy and a position-sensitive detector for the determination of the emission position. To estimate its feasibility, we performed the Monte Carlo simulations using the Geant4 toolkit. For an iron bulk sample with implanted nickel elements, we could recognize the shape of the nickel implant from the 2D image obtained by the imaging system using the energy information of characteristic prompt gammas emitted by neutron capture interactions.

[en] This study aimed to verify that neutron energy and flux can be simultaneously measured by a new technique called an array-type threshold detector. Neutrons generated by nuclear reactions between 26 MeV protons and beryllium targets in the KIRAMS MC50 cyclotron were measured using array-type threshold detectors fabricated by superimposing 4 arraytype activation foils composed of Au, Ag, In, and Cu, and the measured results were compared to the simulation results using MCNPX and FISPACT. The results showed that the spatial distribution of high-speed neutrons was mostly concentrated at the center of the beam, whereas the thermal neutrons were relatively sparse at the center of the beam. The results show that although there is a difference between the experiment and the simulation, the high-speed neutron results showed a common tendency for the neutron flux to be concentrated on the center part compared to the total flux. The thermal neutron results showed a trend in which the thermal neutron flux became less at the central part compared to the total flux

[en] Nowadays, evaluation of amounts and distributions of radioactive waste is an important preparatory step in the process of nuclear reactor decommissioning. For tentative estimation of radioactive waste, a cell-based rigorous 2 step (R2S) method usually is used; however, a poor resolution caused by the averaged flux and spectrum in a cell is still a great challenge because of leading to underestimated or overestimated results. To overcome the poor resolution, several systems were introduced. Neither system, however, provides any function for evaluation of radioactive waste amount and distribution. Thus, it is additionally required to classify radioactive waste based on the results of activation calculation. In this study, the advanced R2S (AR2S) system was developed. To verify the performance of the system, its results for a verification problem were compared with those of the cell-based R2S method. The results showed good agreement, which is to say, within 2.0% relative error. Also, several characteristics of fine/coarse mesh were analyzed. To demonstrate the performance of the AR2S system, the radioactive waste from the Japan Power Demonstration Reactor (JPDR) was estimated, and the result indicated a high-resolution distribution. Therefore, it is expected that the AR2S system will prove useful for precise evaluation of radioactive waste

[en] A digital twin system for a gamma-ray spectrometer was developed using the Geant4 Monte Carlo simulation toolkit and a dedicated novel methodology. The model system was verified to accurately represent the intrinsic characteristics of gamma-ray detection systems: not only Gaussian energy broadening caused by energy resolution, but also count loss and coincidence summing caused by the dead time and charge collection time, respectively, of the detector system. In order to represent the time-related phenomena, the results of the Monte Carlo simulation were printed out in list-mode data rather than (as in existing previous studies) as a simple energy spectrum. The list-mode data were then post-processed considering the characteristics of the gamma-ray detection systems. The model system was verified by comparison with real-world experimental data using radiation sources (¹³⁷Cs and ⁶⁰Co) and a high-purity germanium detector, the results of which showed that the spectra generated by the model well matched the experimental spectra throughout the entire energy range (0–3 MeV), with correlations of 94.3 and 94.6% for ¹³⁷Cs and ⁶⁰Co, respectively

[en] Direct stamping of functional materials has been developed for cost-effective and process-effective manufacturing of nano/micro patterns. However, there remain several challenging issues like the perfect removal of the residual layer and realization of high aspect ratio. We have demonstrated facile fabrication of flexible strain sensors that have microscale thick interdigitated capacitors with no residual layer by a simple direct stamping with silver nanoparticles (AgNPs). Polyurethane (PU) prepolymer was utilized as an adhesive layer to transfer AgNPs more efficiently during the separation step of the flexible stamp from directly stamped AgNPs. Scanning electron microscopy images and energy dispersive x-ray spectroscopy analysis revealed residue-free transfer of microscale thick interdigitated electrodes onto two different flexible substrates (elastomeric and brittle) for the application to highly sensitive strain sensors. (paper)

[en] In order to trace the origin of Particulate Matter (PM) in Korea, the research was conducted to analyze the nuclide of PM samples. To analyze the PM sample, we performed Backtracking Analysis and Gamma spectroscopy. PM is affected by the size of the atmospheric mixing layer height and the air flow according to the air mass. The air flow of the 2 seasons (summer and autumn) was predicted by using Hysplit (backtracking analysis). And the radioactivity of nuclides in the PM sample collected from the measuring site is confirmed using gamma spectroscopy and radioactivity calculation method. Takuya (J Nuclear Radiochem Sci, 8(1):5-9, 2007) As a result of analyzing samples collected in 2 seasons, it was confirmed that the radioactivity of specific nuclides changed according to the season and was affected by air flow. In conclusion, the origin of PM can be estimated by confirming the change in PM and nuclides. (author)