[en] The steady-state behavior of recycling neutral atoms in a tokamak edge region has been analyzed through a two-dimensional Monte Carlo simulation. A particle tracking algorithm used in earlier research on the neutral particle transport is applied to this Monte Carlo simulation in order to perform more accurate calculations with the EDGETRAN code which was previously developed for a two-dimensional edge plasma transport in the authors' laboratory. The physical model of neutral recycling includes charge-exchange and ionization interactions between plasmas and neutral atoms. The reflection processes of incident particles on the device wall are described by empirical formulas. Calculations for density, energy, and velocity distributions of neutral deuterium-tritium atoms have been carried out for a medium-sized tokamak with a double-null configuration based on the KT-2 conceptual design. The input plasma parameters such as plasma density, ion and electron temperatures, and ion fluid velocity are provided from the EDGETRAN calculations. As a result of the present numerical analysis, it is noticed that a significant drop of the neutral atom density appears in the region of high plasma density and that the similar distribution of neutral energy to that of plasma ions is present as frequently reported in other studies. Relations between edge plasma conditions and the neutral recycling behavior are discussed from the numerical results obtained herein. (author)

[en] The effects of pulsating flow, such as pulsating frequency and flow rate, on the heat transfer as well as pressure drop in a plate heat exchanger has been studied in detail. Reynolds number in cold side of a plate heat exchanger is varied 100∼530 while that of hot side is fixed 620. The pulsating frequency is considered in the range of 5∼30Hz. The result of the pulsating flow are also compared with those of steady flow. It is found that the average heat transfer rate as well as pressure drop is increased as flow rate is increased for both steady flow and pulsating flow cases. When pulsating flow is applied to the plate heat exchanger, heat transfer could be substantially increased in particular ranges of pulsating frequency or Strouhal number; St=0.36∼0.60 and pressure drop is also increased, compare with those of steady flow

[en] The collimator system could be used to demonstrate correlation between distal dose falloff and prompt gamma distribution, but it is difficult to be used in practice considering that the system has to be moved when the therapy beam is scanned. The system in fact has to measure both the direction and location of incident prompt gamma to be stationary. We chose to use a newly developed Compton gamma detector system consisting of a time projection chamber (TPC) and a position sensitive gamma camera. TPC is a gas detector with a printed circuit board to track scattered elections. We have performed extensive Monte Carlo simulations using GEANT3 to evaluate the use of the Compton camera to detect distal dose falloff and also to optimize the geometry. The result predicts that the number of gamma detected at a beam current of 5 nA is around 2000 per sec. Also, effects of dimensions and energy resolution of each electron and gamma detector on the efficiency of the whole detector system were evaluated. Based upon simulation results, a pixellated CsI(Tl) detector with position sensitive PMT and electronics to manipulate the signals are fabricated for testing. It is beyond the scope of user program to fully develop the system, and thus we studied key components of the system. The proton beam has the advantage of distal dose falloff over conventional radiation therapy modalities using photons and elections. However, it can be disadvantageous unless the falloff location matches accurately with the distal end of tumor volume. In the early stage of this research project we chose to measure prompt gamma emitted in the orthogonal direction to the beam using a collimator to locate dose falloff location

[en] Cathodoluminescent (CL) spectra of Li-doped Gd_2-xY_xO₃:Eu³⁺ solid-solution (0.0≤x≤0.8) were investigated at low voltages (300 V-1 kV). The CL intensity is maximum for the composition of x=0.2 and gradually reduces with increasing the amount of substituted Y content. In particular, small (∼100 nm) particles of Li-doped Gd_1.8Y_0.2O₃:Eu³⁺ are obtained by firing the citrate precursors at only 650 deg. C for 18 h. Relative red-emission intensity at 300 V of this phosphor is close to 180% in comparison with that of commercial red phosphor Y₂O₃:Eu³⁺. An increase of firing temperature to 900 deg. C results in 400-600 nm sized spherical particles. At low voltages (300-800 V), the CL emission of 100 nm sized particles is much stronger than that of 400-600 nm sized ones. In contrast, the larger particles exhibit the higher CL emission intensity at high voltages (1-10 kV). Taking into consideration small spherical morphology and effective CL emission, Li-doped Gd_1.8Y_0.2O₃:Eu³⁺ appears to be an efficient phosphor material for low voltage field emission display

[en] Absolute value of the functional data of gated myocardial perfusion SPECT is necessary to determine that individual patient is normal or not. Tc-99m MIBI gated myocardial perfusion SPECT was performed using emory cardiac tool box program. All patients (M:F=15:36, age 64±10 yrs) showed normal myocardial perfusion. The patients with following characteristics were excluded; previous angina or MI, ECG change with Q wave or ST-T change, diabetes mellitus, hypercholesterolemia, typical chest pain and hypertension. In all patients, myocardial mass is 117±23 g in stress gated SPECT, 106±22 g in stress ungated SPECT and 102±21 g in rest ungated SPECT. EDV is 90±28 ml, ESV 26±20 ml, SV 66±21 ml, EF 73±10 % and TID 1.06±0.14. Myocardial mass in rest ungated SPECT is significantly different between men and women (p=0.025). Myocardial mass is significantly different between stress gated SPECT and stress ungated SPECT (p=0.000), and between stress ungated SPECT and rest ungated SPECT (p=0.003). We provide normal value of functional parameters to determine the abnormality of individual patients in patients with low risk of coronary artery disease

[en] The objective of the present work is to verify the prediction and analysis capability of MELCOR code about the progression of severe accidents in light water reactor and also to evaluate appropriateness of thermal-hydraulic models used in MELCOR code. Comparing the results of experiment and calculation with MELCOR code is carried out to achieve the above objective. Specially, the comparison between the CORA-13 experiment and the MELCOR code calculation was performed

[en] A survey and analysis of India's nuclear policy, nuclear program, nuclear liability, nuclear R&D program, and education and training program for nuclear personnel were conducted. In addition, the current status of bilateral cooperation with the main focus on the collaborative research project launched, and a bilateral cooperation meeting held to identify the best ways to promote cooperation was described, while ramifications and future directions for mutually beneficial cooperation was suggested. To this end, the project team members visited India to receive specialized consultation from Indian experts.

[en] The final objective is to develop the technical criteria for the facility operation of the interim spent fuel storage facility. For this purpose, elementary technical issues are evaluated for the wet storage of spent fuels and status of operation in foreign counties are examined. Urgent objective of this study is to provide technical back data for the development of operational criteria. For the back data for the development of operational criteria, domestic technical data for the wet storages are collected as well as standards and criteria related to the spent fuel storage. Operational stutus of spent fuel storages in foreign countries CLAB in Sweden and MRS in the United States are studied. Dry storage concept is also studied in order to find the characteristics of wet storage concept. Also basic technical issues are defined and studied in order to build a draft of operational criteria

[en] Zirconium carbide has been chosen and studied as an advanced material of silicon carbide. In order to collect data on the basic properties and characteristics of Zirconium carbide, studies have been conducted using various methods. As a result of chemically vapor deposed subliming zirconium tetrachloride(ZrCl4) and using methane(CH4) as a source in hydrogen atmosphere, graphite film is deposited.. Zirconium carbide was deposited on the sample where silicon carbide was deposited on a graphite substrate using Zirconium sponge as a Zirconium source. In terms of physical characteristics, the deposited Zirconium carbide showed higher strength, but slightly lower elastic modulus than silicon carbide. In order to evaluate the mechanical properties of a coating layer in pre-irradiation step, internal pressure induced method and direct strength measurement method is carried out. In the internal pressure induced method, in order to produce the requirement pressure, pressure media is used. In the direct strength measurement method, the indentation experiment that indent on a hemisphere shell with plate indenter is conducted. For this method, the finite element analysis is used and the analysis is verified by indentation experiments. To measure the strength of TRISO particle SiC coating, SiC hemisphere shell is performed through grinding and heat treatment. Through the finite element analysis, strength evaluation equation is suggested. Using suggested equation, Strength evaluation is performed and the strength value shows 1025MPa as a result of statistical analysis

[en] In order to enhance system maintainability, control stability and availability, various design changes have been implemented in the Chemical and Volume Control System (CVCS) of the Korean Standard Nuclear Power Plant (KSNP). A CVCS simulation code, CARD, which models the letdown and charging system has been developed to demonstrate the performance of the CVCS. The code was preliminarily and partially verified by comparing its simulation results with the measured data during transient operation in the previous CVCS letdown system with flow control valves. In this study, the integrated system performance is evaluated by simulating the CVCS transients during the performance related design basis events using the CARD code and comparing the simulated results with the field test results. The analysis results show that the CVCS can perform its functions without any unacceptable transients during the performance related design basis events and that the code can predict the actual plant test results well