[en] A composite stilbene scintillator has been specially developed for fast neutron detection. The detector response have been measured by using gamma, alpha, neutron radiation source and mono-energy neutron from the Tandem Van de Graff accelerator, and compared to the performance of the commercial single stilbene crystal. In this study, the detection and separation performance for gamma-ray and neutron were evaluated and compared with the single stilbene crystal. The composite stilbene scintillation detector could be possible to use the fast neutron detection in the various fields. The relative light yields of the composite stilbene scintillator comparing to the commercial single stilbene crystal are 81% for the gamma-radiation and 70% for the alpha particles. The calculated value of the relative neutron detection efficiency for composite stilbene scintillator is 53.5 % while the detection efficiency is assumed as 100% for the commercial single stilbene crystal. For ²⁵²Cf neutron radiation source, the Figure-of-Merit of single stilbene crystal was 1.21, and that of the composite stilbene scintillator was 0.95. The property measurement result says that our composite stilbene scintillator has similar characteristics to the single crystals for the radiations, such as gamma-rays, alpha particles, and fast neutrons. The advantages of the composite stilbene scintillators are large construction, no special housing, and no toxic. The major aim of this research, the n/γ separation performance of the large area composite stilbene scintillator is similar with the commercial single stilbene crystal for the neutron radiation source and mono-energy neutron generated through Tandem Van de Graff accelerator. The measurement techniques for the fast neutrons will be applied to the neutron monitoring system in the nuclear fusion reactor, and also can contribute to the nuclear data production in Korea

[en] The optimum test conditions of measuring the crack height were determined for the two-probe ultrasonic diffraction method. The applicability and the accuracy of the two-probe ultrasonic diffraction method on the inclined artificial cracks and the fatigue cracks were evaluated. It is possible to measure the height of the normal and inclined artificial cracks with the maximum error of ± 0.5mm with the two-probe ultrasonic diffraction method. It was found, however, that the accuracy of this method in measuring the height of the fatigue crack depends on the degree of closure of the crack tip. It was desirable to choose a refraction angle as small as possible, but the angle should not be so small that the distortion of the lateral waveform became appreciable

[en] Organic single crystal stilbene has the best spectrometry characteristics and light yield in comparison with plastics and liquids and has been widely used as neutron detectors or monitors due to their fast timing response and good pulse shape discrimination (PSD) properties in neutron/gamma mixed fields such as a particle accelerator, a generation IV nuclear reactor, a nuclear fusion reactor, and so on. However, single stilbene crystals are so difficult to obtain in large size that greater than 60-80 mm in diameter, and are also vulnerable to damage from thermal and mechanical shocks that its extensive use are limited. Recently, polycrystal composite stilbene based on grains of stilbene crystals have been developed in several Research Institute and it is manufactured in large size for neutron detection. We have investigated its characteristics, especially capability of neutron /gamma discrimination

[en] The stilbene scintillator was proposed as a neutron-flux monitor in measuring the characteristics of neutron radiation at the Korea Superconducting Tokamak Advanced Research (KSTAR). Various neutron diagnostic tools are used in fusion reactors for measurement of plasma parameters such as fusion power, power density, ion temperature, fast ion energy, and their spatial distribution. In this study, to evaluate the properties of the stilbene neutron diagnostic system, the efficiency of the radiation shielding was tested experimentally by changing the orientation of the n, γ source. Polyethylene was used to keep neutrons out of the sight line and gamma-rays were blocked by lead. A neutron tagger module was used for a signal digitization, which consists of Flash-ADC and FPGA implemented with real-time n-γ separation processor by using a charge comparison method. As a result, the designed and fabricated stilbene neutron diagnostic system show a good performance measuring neutrons and it was proper as the collimator to measure neutrons from fusion reaction at KSTAR

[en] Pulmonary venous wedge angiogram (PVWA) was performed in 23 patients with cyanotic congenital heart disease due to decreased pulmonary blood flow, as the part of whole of pulmonary arterial system had not been opacified by conventional angiogram. The pulmonary venous wedge angiogram visualized pulmonary arteries (1) with completely closed feeder or with severe peripheral stenosis in 16 patients with pulmonary atresia or TOF, (2) with the interruption of one pulmonary artery in 3 patients, and (3) in 4 patients with tight pulmonary stenosis where pulmonary arteries were not adequately delineated. PVWA has completed the map of entire pulmonary arterial system, which was essential in the surgical management of these patients

[en] Highlights: • A chromium oxide layer is formed as diffusion barrier by thermal oxidation process on STS substrate. • A Cr_2O_3 layer effectively reduces impurities diffusion into the CIGS absorber layer. • The Cr_2O_3 layer plays an important role in increasing the efficiency by reduction of impurity diffusion. - Abstract: It is known that the efficiency of flexible Cu(In,Ga)Se_2 (CIGS) solar cells fabricated on stainless-steel (STS) substrates deteriorates due to iron (Fe) and Cr impurities diffusing into the CIGS absorber layer. To overcome this problem, a nanoscale homomorphic chromium oxide layer was formed as a diffusion barrier by thermal oxidation on the surface of STS substrates for 1 min at 600 °C in oxygen atmosphere. By TEM and grazing-incidence X-ray diffraction (GIXRD), it was confirmed that the formed oxide layer on surface of STS substrates was a Cr_2O_3 layer. It was found that the formed homomorphic Cr_2O_3 thin layer of about 15 nm thickness was an effective diffusion barrier to reduce impurity diffusion into the CIGS layer by secondary ion mass spectroscopy (SIMS). In contrast to the efficiency of CIGS solar cell without homomorphic Cr_2O_3 diffusion layer is 8.6%, whereas with diffusion barrier it increases to 10.6% because of impurities such as Fe and Cr from the STS substrate into the CIGS layer. It reveals that the layer formed on the surface of STS substrate by thermal oxidation process plays an important role in increasing the performance of CIGS solar cells.

[en] In this study, neutron detection efficiency of the UNDA system, which has been developed for study on nuclear material accountancy in a future pyro-process facility, was evaluated by using the MCNPX code. The detection efficiency was evaluated as a function of (1) positions of ²⁵²Cf neutron source in the axial and radial directions, and (2) thicknesses and locations of the container filled with the depleted uranium materials for two different designs of the UNDA. In the case of ²⁵²Cf source positions, detection efficiency was distributed from 6.83% to 13.35%. As ²⁵²Cf source was positioned at upper part in the axial direction, detection efficiency was decreased after a slight increase. On the other hands, as source was positioned at outer part in the radial direction, detection efficiency was increased. In the case of container thickness, there was a slight decline when the thickness was increased. As the container was located at upper part, detection efficiency was decreased and as the container was located at outer part, detection efficiency was increased. Detection efficiency was varied from 10.31% to 13.61%. These values were higher than that of ²⁵²Cf source case. The UNDA with polyethylene cover has about 2% higher detection efficiency than the UNDA without the cover

[en] We studied the angiographic findings in 65 patients with congenital pulmonary atresia, ages 4 days to 14 years (mean 3.3 yrs), from 1981 to 1986 at Severance Hospital Yonsei University. 1. 6 had pulmonary atresia with an intact interventricular septum, 38 had it with cardiac anomaly Renodynamically simulating TOF, and 21 associated with more complicated cardiac anomalies. 2. In the group with an intact ventricular septum, 5 showed confluent intrapericardial pulmonary artery, all segmental pulmonary arteries connected to intrapericardial artery. 3. In the group simulating TOF, aorta arose from RV with or without overriding in 35. In 27 patients with confluent intrapericardial pulmonary artery, 23 had more than 10 segmental pulmonary arteries connected to intrapericardial artery and 5 had severely hypoplastic hilar pulmonary arteries. In 11 with non confluent intrapericardial pulmonary artery, 4 had more than 10 segmental pulmonary arteries connected to central pulmonary artery and 9 had severely hypoplastic hilar pulmonary arteries. 4. In the group associated with more complicated cardiac anomaly, included 8 patients with atrioventricular discordance, 7 with univentricular heart and 6 with tricuspid atresia. In 17 patients with confluent intrapericardial artery, 16 had more than 10 segmental pulmonary arteries connected to intrapericardial artery, one showed severe hypoplasia of hilar pulmonary arteries. In another 4 with non confluence, no one showed more than 10 segmental arteries connected to intrapericardial or hilar pulmonary artery.

[en] Thermoluminescence dosimeter (TLD) is a detector that represents personal dosimeter in many years. Recently, dose re-evaluation in personal dosimetry is gradually required because it makes the measurement system more reliable as offering a chance to repeat the measurement. Compared with OSLD (Optical stimulated luminescence dosimeter), dose re-evaluation using TLD was considered impossible due to erase process of trap charge during high temperature measurement. These values are quite effective for dose re-estimation, which is mainly used for highly exposed persons. In fact, the routine personal dosimetry service measures TL every quarter. Therefore, it is difficult to take into the PTTL reset, but accumulation of the signal by quarterly recorded dose become a problem. Furthermore, because the PTTL signal decreases with the number of TL measurements, the decrease in cumulative PTTL signal should also be considered. A normalized PTTL signal according to the number of serial TL measurements is presented in Fig. 4. The data shows the exponential decay with the TL measurement. Consequently, since the PTTL signal is maintained more than 10% after 5 TL measurements, the correction should be made especially for the highly exposed TLD.

[en] The XRF technique compares the measured pulse height of U and Pu peaks which are self-induced characteristic xray emitted from U and Pu to quantify the elemental U and Pu. The measurement of the U and Pu x-ray peak ratio provides information on the relative concentration of U and Pu elements. Photon measurements of spent nuclear fuel using high resolution spectrometers show a large background continuum in the low energy x-ray region in large part from Compton scattering of energetic gamma-rays. The high Compton continuum can make measurements of plutonium x-rays difficult because the relatively small signal to background ratio produced. In pressurized water reactor (PWR) spent fuels with low plutonium contents (-1%), the signal to background ratio may be too low to get an accurate plutonium x-ray measurement. The Compton suppression system has been proposed to reduce the Compton continuum background. In the present study, the feasibility of a Compton suppression system for XRF was evaluated by Monte Carlo simulations and measurements of the radiation source. In this study, the feasibility of a Compton suppression system for XRF was evaluated by MCNP simulations and measurements of the radiation source. Experiments using a standard gamma-ray source showed that the peak-to-total ratios were improved by a factor of three when the Compton suppression system was used