• Nuclear Engineering and Technology
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• v.13 no.4
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• pp.264-276
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• 1981

A simulation procedure which can represent time-dependent nuclear characteristics of TRIGA Mark-III reactor is developed. CITATION, a multi-group diffusion-depletion program, has been utilized as calculational tool. The group structure employed in this study consists of 7 groups: -3-fast and 4-thermal-which is conventionally utilized in TRIGA type reactor analysis. Three-dimensional nuclear characteristics are synthesized by combining results from two-dimensional plane calculation and two-dimensional cylinder calculation, since direct three-dimensional approach is not yet possible. An effort ia made to develope a method which can extract effective zone and group dependent bucklings by neutron diffusion theory rather than conventional zone and/or group independent Ducklings by neutron transport theory, since neutron leakage is quite high for small core such as research reactors. It is turned out that the method developed in this study gives satisfactory results. The calculation is performed under assumptions that all control rods are fully withdrawn, that no samples are inserted in the irradiation holes and that the core is located in the center of the reactor pool. Burnup-dependent variation of core excess reactivity, time dependent change of Xe-135 poisoning and reactivity worth of rotary specimen rack are calculated and compared with operation records. Neutron flux and power distribution as well as neutron spectrum in each irradiation .facility are presented.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.485-490
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• 2005

Effects of gas injectino on the copper recovery form industrial waste water in a fluidized-bed electrolytic reactor were investigated. Effects of gas injection on the individual phase holdup and efficiency of copper recovery for given operating variables such as liquid and gas velocity (0.1~0.4 cm/s), current density ($2.0{\sim}3.5A/dm^2$) and amount of fluidized solid particles (1.0~4.0 wt%) were examined. The solid particle, whose diameter and swelling density were 0.5 mm and $1100kg/m^3$, respectively, was made of polystylene and divinyl benzene. It was found that the holdup of gas and solid phases increased, but that of the liquid phase decreased with increasing velocity of gas injected into the reactor. With increasing gas and/or liquid velocity and increasing amount of fluidized particles is not needed, the rate of copper recovery increased to a maximum value of and subsequently decreased. The recovery rate of copper increased almost linearly with increasing current density in accordance with Faraday's law.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.435-441
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• 2014

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

• Journal of Environmental Health Sciences
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• v.32 no.1 s.88
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• pp.71-76
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• 2006

Treatment performance and microbial community structure were investigated in water-soluble cutting oil treatment process using biological activated carbon. DOC removal in BACI column at $15^{\circ}C$ was higher than at $25^{\circ}C$, but those of BAC3 column after 60days was high at$25^{\circ}C$. Also, quinone content of first-step reactors at $25^{\circ}C$ and $15^{\circ}C$ was much the same, but those of the third-step reactor at $25^{\circ}C$ was higher than at $15^{\circ}C$. The dominant type of two apparatus was ubquinone (UQ)-l 0 followed by UQ-8. Menaquinones were detected from $25^{\circ}C$ apparatus and effluent. This suggested that DOC removal at $25^{\circ}C$ was advanced degradation by attached microorganisms on the activated carbon surface. The DOC removal in long-term activated carbon apparatus increased with going in BAC3 column. This indicated the influent of POC was a result of DOC removal efficiency decrease. Integrated DOC removal from start point in experiment to break point and quinone content were showed a tendency of increasing with going last-step activated carbon apparatus. Therefore, the biological activated carbon apparatus used by this study was effective treatment process in contaminated groundwater by water-soluble cutting oil.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.458-463
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• 2005

Considering the characteristics of a filtration bio-reactor equipped with a mesh filter module which can effectively maintain high concentration of biomass and enhanced solid-liquid separation performance, the hybrid process of filtration bio-reactor combined with coagulation was investigated to get improved filtration characteristics as well as water quality in this work. Two bio-reactors (Run-1 & Run-2) were operated under the following conditions: working volume of 25 L, continuous loading of a synthetic wastewater (BOD: 200 mg/L, T-N: 50 mg/L, T-P: 5 mg/L), where an appropriate amount of alum ($Al_2(SO_4)_3{\cdot}18H_2O$) was added once a day into the reactor (Run-2). In the system without using a alum (Run-1), the clogging of mesh filter module was observed two times through 85 days of whole operation. Meanwhile, the filter module did not clog even at higher MLSS concentration (6,000~12,000 mg/L) and the stable filtration (0.7 mid) was continued in the case of using a alum. Due to the stable formation of cake layers, BOD and SS were shown below 6 and 3 mg/L, respectively. T-P and pH of the effluent were changed because of the intermittent addition of the alum. In the case of Al/P=2.5, the average T-P removal efficiency per day was 85.2% and the average T-P concentration of the effluent was 0.3 mg/L. However, the removal efficiency of phosphate was influenced by pH in the reactor.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.547-555
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• 2009

The objectives of this research were focused on the effects of various operating parameters on nitrous oxide emission such as C/N ratio, ammonia concentration and HRT in the hybrid and suspension reactors. With the decreasing of C/N ratios, $N_2O$ emission rates in the both processes were increased because organic carbon source for denitrification was depleted. In case of biofilm reactor operated using medium, $N_2O$ release from the nitrification was not affected by the variation of ammonia concentration. But in the suspension reactor, $N_2O$ production from the nitrification was rapidly increased with the increase of ammonia. Nitrite accumulation caused by undesirable nitrification conditions could be a important reason for the increase in the $N_2O$ production from the aerobic reactor. And rapid increase in $N_2O$ production was reflected by the decrease of HRT, similar to the results observed in the results of ammonia loading changes. So it could be said that it is very important to put in consideration both its optimum conditions for wastewater treatment efficiency and suitable conditions for $N_2O$ diminish, simultaneously, in order to development an eco-friendly and advanced wastewater treatment, especially in BNR process.

• Korean Journal of Microbiology
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• v.42 no.1
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• pp.26-33
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• 2006

To understand the efficient process of biological nitrogen removal (BNR) system, the structure of bacterial communities in nitrification reactors was analyzed using PCR and terminal restriction fragment length poly morphism (I-RFLP) methods. In this study, we used an advanced treatment system with plotting media, Nutrient Removal Laboratory system, or the rumination type sequencing batch reactor (SBR) system. The terminal restriction fragments of ammonia-oxidizing bacteria (AOB) and other $\beta-proteobacteria$ were observed in all of three BNR systems. The nucleotide sequence analysis of terminal restriction fragments showed that Nitrosomonas and Nitrosolobus were major populations of AOB in SBR system, whereas uncultured $\beta-proteobacteria$ and Cardococcus australiensis were the predominant groups in other two BNR systems. Also the SBR system may be more efficient to enrich AOB. These results indicate that the different structure of bacterial community may be developed depending on the wastewater treatment systems, although the same influent is used.

• Nuclear Engineering and Technology
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• v.9 no.4
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• pp.223-236
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• 1977

An integral computer code has been developed for a mechanical and thermal design and performance analysis of an oxide fuel rod in a pressurized water reactor. The code designated as FROD 1.0 takes into account the phenomena of radial power depression within the pellet, cracking, densification and swelling of the pellet, fission gas release, clad creep, pellet-clad contact, heat transfer to coolant and buildup of corrosion layers on the clad surface. The FROD 1.0 code yields two-dimensional temperature distributions, dimensional changes, stresses, and internal pressure of a fuel rod as a function of irradiation time within a reasonable computation time. The code may also be used for the analyses of oxide fuel rods in other thermal reactors. As an application of FROD 1.0 the behavior of fuel rod loaded in the first core of Go-ri Nuclear Power Plant Unit 1 is predicted for the two power histories corresponding to steady state operation and Codition II of the ANS Classification. The results are compared with the design criteria described in the Final Safety Analysis Report and a discrepancy between these two values is discussed herein.

• Journal of the korean society of oceanography
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• v.33 no.1-2
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• pp.35-40
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• 1998

In February and April 1997, three temporary interruptions of electric power production at the Uljin Nuclear Power Plant in the east coast of Korea were caused by the malfunction of the cool-ing-water supply unit. The clogging of the drum screens inside the unit caused by the surface swarm of the euphausiid Euphausia pacifica Hansen might be responsible for the malfunction. These incidents were of particular interest since such interruption of reactors' operation by krill swarms had not previously been reported. Using samples caught by the drum screens inside the cooling water-supply unit, we investigated the population structure of surface swarms. One occasion of nighttime and three occasions of daytime surface swarms were found in February and April 1997, respectively. The foreguts of more than 60% of E. pacifica in nighttime surface swarm were in full condition. This evidence suggests that E. pacifica aggregates to the surface water at night for feeding. In daytime surface swarms consisting of mature E. pacifica, however, foreguts in full condition were only found in less than 10eio of krill examined, suggesting that daytime surface swarms are closely related to breeding activity. During the study period, the growth rate of mature females was more than twice higher than that of mature males. Analyses of the sex-ratio and length-frequency data show a decrease in the portion of males with increasing size. There was a decline in the number of males of 19 mm in length. Energy loss during spermatophore transfer may result in the death of male E. pacifica, as found in male E. superba.

• Korean Journal of Microbiology
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• v.44 no.1
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• pp.29-36
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• 2008

Nitrogen is one of the major pollutants that should be removed by wastewater treatment systems. Biological nitrogen removal (BNR) is a key technology in advanced wastewater treatment systems operated by bacterial populations. Nitrification is the first step of microbiological processes in BNR system. Ammonia is oxidized to nitrite by ammonia-oxidizing bacteria (AOB) and then nitrite is subsequently oxidized to nitrate by nitrite-oxidizing bacteria (NOB). The diversity of NOB in nitrification reactors of 3 BNR systems, Edited biological aerated filter system, Nutrient removal laboratory system, and the Rumination type sequencing batch reactor system, was investigated by terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes. Cluster analysis of T-RF profiles showed that communities of Nitrobacter group in each system were different depending upon the process of systems. However, the clusters of Nitrospira group were divided by the habitat of aqueous and solid samples.