[en] Alpha particle spectrometry with collimation is a useful method for identifying nuclear materials among various nuclides. A mesh type collimator reduces the low energy tail and broadened energy distribution by cutting off particles with a low incidence angle. The relation between the resolution and the counting efficiency can be investigated by changing a ratio of the mesh hole diameter and the collimator thickness. Through collimation, a target particle can be distinguished by a PIPS"® detector under a mixture of various nuclides. - Highlights: • Alpha particle spectrometry with collimation a useful method for identifying nuclear materials among various radionuclides. • A collimator cut off alpha particles with low angle emitted from a source. • We confirm that that a collimator improves the resolution of alpha spectra through both simulation and experiments

[en] L-edge densitometry (LED) which is specially called X-ray Absorption Spectrometry (XAS) for uranium xray analysis is a technique of determination of uranium concentration as a continuous x-ray energy beams transmit a uranium liquid sample for safeguard. Compared to K-edge densitometer, since relatively lower energy of uranium L series energy than K series energy, L-edge densitometer does not require a liquid nitride cooling system. In this study, the simulation of uranium L-edge densitometer is performed using Monte Carlo method. Ledge spectrum, such as spectrum jumps, can be confirmed by the simulation. In further study, improvement of counting efficiency through collimation of x-ray, and shielding will be considered for detailed design of L-edge densitometer

[en] Iodine behavior is most important in the evaluation of the early effects of a severe accident on the off-site public health. However, the MELCOR code, which is being used by Korea Institute of Nuclear Safety (KINS) for an integrated severe-accident assessment, does not treat the organic iodine behavior in the containment atmosphere. Therefore, it is needed to develop a standalone model which can be coupled with the current radiological assessment methodology. KINS agreed with other domestic organizations, including Korea Atomic Energy Research Institute (KAERI), Korea Hydro and Nuclear Power Co. Ltd. (KHNP) and KEPCO Engineering and Construction Company, Inc. (KEPCO E and C), to participate in the ISTP (International Source Term Program) operated by IRSN. This Program investigates the behaviour of iodine and ruthenium in the containment of a power plant in case of severe accident. It consists of two sub programs: ISTP-EPICUR and PARIS. This study was carried out to evaluate the experimental results and derive observations that could be used for development of an iodine behavior model and its validation

[en] Alpha spectroscopy is widely used for detecting undeclared nuclear facilities, activities, and materials. Due to the heavy equipment required to carry out this technique, its applications is limited. With the goal of quickly and efficiently responding to undeclared nuclear facilities, activities, and materials, the present authors have designed and built a portable α-particle spectrometer. This study was conducted in order to develop a new portable α-particle spectrometer with the purpose of detecting undeclared nuclear facilities, activities, and materials on site quickly and efficiently. All heavy and large components, which are typically required for a laboratory such as a αparticle spectrometry system, were minimized and placed in a small container with a weight of 14 kg and a size of 30 cm x 30 cm x 30 cm. In the feasibility study, the calculated enrichment values of "2"3"5U obtained from the portable α-particle spectrometer were 1.868 % and 3.083 %, similar to the results from a commercial spectrometry system used in laboratories, 2.049 % and 3.253 %. These differences were possibly caused by different channel setups for each system

[en] This analysis can be used to identify the undeclared nuclear activities of North Korea. The international community has developed a method of collecting and analyzing uranium particles within a limited time in the field to determine whether or not undeclared nuclear activities have taken place. This study shows the U source using CeF_3 coprecipitation has no significant difference. In addition, this CeF_3 coprecipitation method is simple and time saving. It is expected to be useful for rapid on-site detection of undeclared uranium enrichment activities

[en] Radionuclides such as ¹³¹I, ¹³⁴Cs, ¹³⁷Cs, and ^239,240Pu in Korean rainwater have been analyzed by Korea Research Institute of Standards and Science (KRISS) since the Fukushima nuclear power plant accident in March 2011 to investigate the activity level, distribution pattern, and temporal variation and to assess the radiation dose the public is exposed to. The concentration of ¹³¹I in the Korean rainwater samples varied between 0.033 (minimum detectable activity; MDA) and 1.30 Bq kg^-1 and the concentrations tended to decrease exponentially with time. The concentrations of ¹³⁴Cs and ¹³⁷Cs in rainwater ranged from 0.01 to 334 ± 74 and 0.29 ± 0.01 to 276 ± 1 mBq kg^-1, respectively. The mean activity ratio of ¹³⁷Cs/¹³⁴Cs in the rainwater samples collected from April 18 to May 12 was estimated to be 0.44 ± 0.21, and this value is lower than that (ca. 1) observed in Fukushima, Japan, when there was an escape from the nuclear reactors. When an attempt was made to analyze Pu isotopes in rainwater samples, no Pu isotopes were detected above the MDA in any of the rainwater samples. Although the locations investigated were different from Asia to Europe, the concentrations of ¹³¹I, ¹³⁴Cs and ¹³⁷Cs in the rainwater are comparable, which suggests a global contamination of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs occurred because of the Fukushima nuclear power plant accident. (author)

[en] Electrowinnng is a process to recover uranium and transuranic elements using liquid cadmium cathode (LCC). Major components such as electrodes should be remotely handled and relatively easily replaceable to operate the large-scale electrowinning system. In this paper, the performance of electrodes and LCC crucible was evaluated through cyclic voltammetry (CV) and electrodeposition experiments. In this paper, electrolytic behavior of large-scale LCC electrowinning system was studied. Reasonable CV behavior was obtained using ungrounded power source after dipping of LCC assembly into the electrolytic salt. Electrodeposition experiments were successfully conducted at the current densities of 50 and 70 mA/cm².

[en] Hydrogen combustion phenomenology during severe accidents in nuclear power plants has been a safety issue. Especially, flame acceleration (FA) and Deflagration-to-Detonation Transition (DDT) are important because of their possible destructive impact on the containment or plant systems in it. Accordingly, it is the design goal to avoid FA and DDT for the hydrogen mitigation system. As a result from extensive effort dedicated to resolve the hydrogen issue, compiled information on the FA and DDT has been provided by the NEA. The FA criterion was suggested in terms of the mixture expansion ratio σ , and the criterion for onset of DDT was based on the greatness of the geometrical size of the reactive system compared with the detonation cell width λ of the average mixture composition. The DDT onset criterion reflects the current state of knowledge based on the experimental database; however, the criterion is not sufficient but a necessary condition. Therefore, it should be noted that satisfying this condition means that the possibility of DDT cannot be removed. Based on this information, a simple in-house computer program for evaluation of the FA and DDT possibility, named DEFEND (Determination of Flame Evolution and DDT), is being developed. The database for the density of combustion products analyzed by KEPCO-E and C with the CHEMKIN code was used for FA estimation. The correlation developed by Chan and Wojciechoski is incorporated for determination of the critical expansion ratio σ critical

[en] Highlights: • A various high-refractive-index ZnO patterns were formed on LED using imprinting. • Mechanism of light extraction enhancement was demonstrated by simulation and EL. • Light output power of patterned LED was improved up 19.6% by light waveguide effect. - Abstract: We fabricated high-brightness GaN-based light-emitting diodes (LEDs) with highly refractive patterned structures by using a thermal nanoimprint lithography (NIL). A highly refractive ZnO-nanoparticle-dispersed resin (ZNDR) was used in NIL, and a submicron hole, a submicron high-aspect-ratio pillar, and microconvex arrays were fabricated on the indium tin oxide (ITO) top electrode of GaN-based LED devices. We analyzed the light extraction mechanism for each of the three types of patterns by using a finite element method simulation, and found that the high-aspect-ratio pillar had a great ability to improve light extraction owing to its waveguide effect and prominent scattering effect. As a result, the light output power, which was measured in an integrating sphere, of the LED device was enhanced by up to 19.6% when the high-aspect-ratio pillar array was formed on the top ITO electrode of the device. Further, the electrical properties of none of the patterned LED devices fabricated using ZNDR degraded in comparison to those of bare LED devices

[en] The interest of the people in the radioactive contamination of the water has increased significantly and the study about analysis and management of radioactive materials are being actively conducted. And monitoring spots have been expanded to the range of public water as well as drinking water by publishing the rule of drinking water quality standards and examination in the Environmental Enforcement Ordinance No. 553 of Korea. In this study, US EPA was investigated as the foreign advanced cases and the way that is appropriate for the Korea was sought by analyzing investigate radionuclide, interval and management. As a result, in the selection part of investigate radionuclide, geological survey, status of nuclear power plants and the presence of the use of artificial radionuclides of the Korea should be investigated and additionally after the selection of a few radionuclides, the systems should be extended to cover all possible radionuclides by considering radioactive pollution levels in humans may be exposed due to the annual drinking water. In the part of the investigate interval, the concept(MCL, DL) should be set up for preventing concentration detection of above MCL and it needs to the maintenance and management. For example, when the concentration is more than MCL, it should be investigated on a quarterly and when the concentration is lower than MCL, it should be investigated to each different interval and management. And the US EPA divided the management area and make the road map for managing drinking water. The each classified area has been organized to match the state budget and labor force and the individual data have been managed effectively by HPGe, the NaI, TLD and so on