[en] We introduce our experience in construction and application of the virtual parallel computer using PCs clustered by high speed network cards. MCNP Benchmark calculation using the virtual parallel computer shows that the computing power is proportional to the number of CPUs. The virtual parallel computer with PC cluster has not only economic advantage but also its comparable performace to the high-priced super computer. Current development of compilers and libraries for parallel computing suggests us to consider an ecomonic approach using the virtual parallel computer with PC cluster in scientific and engineering calculations which need long computing time

[en] For the removal of radioiodine from the gaseous effluent streams at nuclear facilities, the adsorption characteristics of elemental iodine(I₂) and methyl iodide(CH₃I) on an unimpregnated and TEDA(Triethylene-diamine) impregnated activated carbons were investigated. Adsorption isotherms were reviewed by various isotherm models such as the Langmuir, the Freundlich, the Sips and the DA (Dubinin-Astakhov) equations, and the DA isotherm equation gave the best fit for the adsorption of I₂ and CH₃I on various activated carbons. The adsorption energy distribution was calculated from the parameters of the DA isotherm equation. The adsorption energy distribution curve for CH₃I on unimpregnated activated carbon showed more sharper than that for I₂. Due to the adsorbate-adsorbent interaction as well as the pore structure, the surface heterogeneity increases as an impregnant content of TEDA increases. The adsorption behaviors of the I₂ and CH₃I on an unimpregnated and TEDA impregnated carbons in fixed bed adsorbers were satisfactorily simulated by the surface diffusion model with the DA isotherm equation

[en] The objectives of this study are to suggest a standard nuclear cooperation agreement (SNCA) as a model for new nuclear cooperation agreements (NCA's) which are expected to be concluded in the near future and to suggest a proposal text and strategy for the revision of existing NCA's with advanced countries such as the United States. To accomplish the objectives, this study: First, establishes a framework for a NCA through clarifying the basic concept of NCA and identifying key elements of NCA. Second, draws implications for a standard NCA and revision of existing NCA's through analyzing by comparison those NCA's between other countries. Third, clarifies the purpose and underlying philosophy for the SNCA, determines the elements to be included in the SNCA, and suggests a final draft of the SNCA. And fourth, clarifies general concepts of the revision of NCA's, analyzes the needs of the revision of the Korea-U.S. NCA, and assesses the position of the United States on the matter. (author). 28 refs., 5 tabs., 2 figs

[en] The after-effect of pharmacologic stress (adenosine) on left ventricular (LV) function, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (LVEF) were evaluated after pharmacologic stress with Tl-201 and ^99mTc-MIBI SPECT using an automated program in 153 subjects. The subjects were grouped as follows: 1) Tl-201 group (n=35, male 18, female 17, mean age: 58 years); normal scan (n=24), ischemia (n=8) and infarction (n=3). 2)^99mTc-MIBI group (n=118, male 60, female 58, mean age: 62 years); normal scan (n=73), ischemia (n=20) and infarction (n=25) based on the interpretation of perfusion images. All patients were in sinus rhythm during the study. 1)Tl-201 group; In patients with ischemia (the mean time interval between injection and acquisition is 12.3 min), post-stress LVEF was significantly depressed after adenosine infusion (51.2 ± 6.3% vs 59.8± 8.2%, p<0.01) and the mean difference in LVEF(ΔLVEF) between rest and stress was 8.6%. Seven patients (88%) showed an increase in LVEF greater than 5% from poststress to rest. The ΔLVEF in the ischemic group was significantly larger than that in the normal scan (p<0.05) or infarction group (p<0.05). 2)^99mTc-MIBI group; In patients with ischemia (the mean time interval between injection and acquisition is 80 min), post-stress LVEF was significantly depressed after adenosine infusion (p<0.001) and ΔLVEF was 5.1%. Eight patients (40%) showed an increase in LVEF greater than 5% from poststress to rest. Poststress ESV (37.1±17.3 ml) was significantly higher than ESV (31.3±15.5 ml, p<0.001) at rest, but no significant difference in EDV. These results showed that pharmacologic stress induced stunning is well noted in the early quantitative gated SPECT in ischemic patients and also observed in the delayed gated SPECT, even though the rate of stunning is less than the early SPECT

[en] Following scope of tasks are performed to establish the nuclear data base which is the infra structure for the nuclear related research and industry. - Upgrade of Table of Nuclides web service and addition of new feature to existing ENDF plotting services. - Establishment of nuclear structures data base. Reconstruction of nuclear structure (ENSDF) data base with up-to-date data. - Establishment of nuclear reaction data base. Collection of the experimental reaction database (EXFOR). Collection of the evaluated nuclear reaction data libraries. Development of data retrieval programs. - Group constant library generation and verification. Generation of MATXS group constant library for thermal reactor application and verification against U-235 cores. Improvement of the cross section library preparation system for the MCNP code. (author). 15 refs., 8 tabs., 8 figs

[en] Treatment technologies for noble gases and semi-volatile gases generated from nuclear fuel cycle process were evaluated, and the optimal process was selected based on process simplicity and safety of disposal. Evaluation of the adsorption capacity of methyl iodine on AgX(silver-impregnated zeolite) and AgS(silver-impregnated silica gel) at the temperature of 80-300 deg C was carried out, and adsorption performances of AgX and AgS were compared with that of activated carbon. CO₂ removal capacity using soda lime, activated carbon and 13X was investigated, and effect of relative humidity was identified. A preparation method of granular calcium hydroxide as a CO-2 removal sorbent using oyster-shells was characterized. This study involves the comparison of the adsorption capacities of Kr on natural or synthetic zeolites and activated carbon at high concentration and an analysis of humidity effect on water adsorption of natural-zeolite. It also was carried out that performance tests for reuse of activated carbon through desorption and re-impregnation process of TEDA/KI impregnated carbon as a removal sorbent for organic radio iodines. (author). 132 refs., 17 tabs., 29 figs

[en] This study aims to analyses recent trends of international situation relating to nuclear non-proliferation and the adverse conditions in Korea's pursuing self-support of such technology, so that it may map out effective strategies for the promotion of nuclear energy. This study analyses developments of international nuclear non-proliferation regime, which plays a main role in preventing the international proliferation of nuclear weapons. This study includes NPT, IAEA safeguards system, international export control regimes, CTBT, and NWFZs as the subjects of analysis. Second theme is international organizations concerning nuclear activities. This study mainly analyses IAEA activities which pursues the promotion of peaceful use of nuclear energy and nuclear non-proliferation simultaneously as a pivotal body of international nuclear cooperation. Third focus of this study is Northeast Asian circumstances pertaining to nuclear non-proliferation. The study looks into the DPRK nuclear issues, and reviews the developments of the proposed regional body for nuclear cooperation and the discussion on the Northeast Asian NWFZ. Fourth, but the most influential to Korean nuclear activities, is the U. S. nuclear policy, since U. S. takes the overwhelming initiative in the field of international nuclear non-proliferation. Therefore, this study gives much weight in analyzing the structure, procedures, recent trend, and pending issues of U. S. nuclear policy. (author). 78 refs., 5 tabs., 4 figs

[en] The adsorption characteristics of methyl iodide (CH₃I) from the off-gas stream on silver impregnated adsorbents such as silver zeolite (AgX), silver silica gel (AgS), unimpregnated carbon were investigated. The removal of radioactive iodine was carried out in the fixed bed by silver impregnated adsorbents, AgX, AgS, and unimpregnated carbon. Effects of temperature, concentration, and impregnated silver amount on the adsorption behaviors were related on the basis of their chemical forms of silver and the adsorbents pore sizes

[en] Hyperfixation characterized by excess tracer activity compared with cerebral blood flow (CBF) using ^99mTc-d, l-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission tomography (SPECT), has not been measured in terms of cerebral metabolic rate of oxygen consumption (CMRO₂) oxygen extraction fraction (OEF) and cerebral blood volume (CBV). We studied four patients with subacute stroke who showed hot uptake in infarct areas with ^99CTc-HMPAO brain SPECT. We performed positron emission tomography (PET) and magnetic resonance (MR) imaging. Regions of interest (ROIs) were drawn in the same hot uptake areas in SPECT and PET images. The average counts per pixel of ^99mTc-HMPAO and the absolute values of CBF, CMRO₂ OEF and DBV with PET were then obtained. The hyperfixation rate with ^99mTc-HMPAO is expressed as the surplus rate compared with PET-CBF. PET parameters in the hot uptake area were compared with those of 5 normal controls. OEF and CMRO₂ at the hot uptake areas in the 4 patients were significantly lower than those of normal controls (P<0.01), but CBF and CBV were not significantly different between patients and normal controls (ns). The hyperfixation rate of 4 patients was 0.30±0.15, which correlated well with CBV (r=0.97, y=11.75 + 0.42 ; P<0.05). The hyperfixation rate by ^99mTc-HMPAO brain SPECT correlated with CBV in the PET study and reflected Gd-DTPA enhancement by MR imaging. Therefore, ^99mTc-HMPAO hyperfixation in the infarct area might be caused by vascular dilatation and disruption of the blood brain barrier in terms of an increased capillary permeability-surface product

[en] Photochemical wet etching of n-type Si (100) was carried out in hydrofluoric acid (49 wt %) solution using high-flux synchrotron x-ray radiation. Under illumination of high-flux white x-ray beam, silicon is electropolished with an etching rate of about 1.5 nm/min. When illuminated with a monochromatic x-ray beam of relatively low flux, a porous silicon layer is formed instead. The open circuit potential increases under the white x-ray beam, in contrast to the results of visible or ultraviolet photoelectrochemistry. The authors attribute the electroless electropolishing of silicon to the enhanced band bending caused by the x-ray illumination