• 상하수도학회지
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• 제24권5호
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• pp.561-572
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• 2010

The efficiency of biological hydrolysis at $80^{\circ}C$ on municipal solid waste mixed with anaerobic digestion sludge was investigated in 100L batch reactors. The hydrolysis effect was observed within a day, when the hydrolysis reactor used for a pre-treatment reactor for methanogenesis, and the effect was observed during two days, When the reactor used for post-treatment reactor. For both configurations, methane production rate decreased, when hydrolysis was carried out more than a day. Gaseous ammonia in the hydrolysis reactors was successtully removed by the ammonia stripping system. Microbial diversity analysis on the hydrolysis reactors indicated dependency of microbial diversity on the configuration of the hydrolysis reactors. Carbohydrate and lactate degrading microbes dominated in the hydrolysis reactor, when the hydrolysis reactor used for a pre-treatment reactor for methanogenesis, while protein degrading microbes dominated in the post-treatment reactor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.133-137
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• 2002

In this paper, the $CF_{4}$ decomposition rate are investigated for a simulated three plasma reactors which are metal particle reactor, spiral wire reactor and reactor with porous dielectric as applied voltage. The $CF_{4}$ decomposition rate by plasma reactor with porous dielectric had a gain of 20~25[%] over that by plasma reactor with spiral wire or metal particle electrode. The $CF_{4}$ decomposition efficiency increases with increasing applied voltage up to the critical voltage for spark formation. The $CF_{4}$ decomposition efficiency of metal particle reactor was about 80[%] at AC 24[kV]. However, decomposition efficiency is more than 90% in case of the reactor with porous dielectric. we think, the reactor with porous dielectric should be much better than other reactors for $CF_{4}$ decomposition.

• 한국안전학회지
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• 제33권5호
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• pp.157-163
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• 2018

This paper describes design improvement to a research rector for safety enhancement using Probabilistic Safety Assessment (PSA). This PSA under reactor design was undertaken to assess the level of safety for the design of a research reactor and to evaluate whether it is probabilistically safe to operate and reliable to use. The scope of the PSA reported here is a Level 1 PSA, which addresses the risks associated with the core damage. The technical objectives of this study were to identify accident sequences leading to core damage and to derive design improvement from the dominant accident sequences through the sensitivity analysis. The AIMS-PSA and FTREX were used for the this PSA of the research reactor. The criterion for inclusion was all sequences with a point estimate frequency greater than a truncation value of 1.0E-14/yr. The final result indicates a point estimate of 6.79E-05/yr for the overall Core Damage Frequency (CDF) attributable to internal initiating events for the research reactor under design. Based on the dominant accident sequences from the PSA, the seven kinds of sensitivity analysis were performed and some design improvement items were derived. When the five methods to improve the safety were all applied to the reactor design and emergency operating procedure, its risk was reduced to about 1.21E-06/yr from 6.79E-05/yr. The contribution of LOCA and LOEP with high CDF were significantly reduced by the sensitivity analysis. The safety of the research reactor was well improved and the risk was reduced than before adapting the design improvement gotten from the sensitivity analysis. The present study indicated that the research reactor has the well-balanced safety in regard to each initiating event contribution to CDF. The PSA methodology is very effective to improve reactor safety in a conceptual design phase and especially, Risk-informed design(RID) is very nice way to find the deficiencies of research reactor under design and to improve the reactor safety by solving them.

• 한국환경과학회지
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• 제8권1호
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• pp.107-113
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• 1999

A new biological nutrient removal system combining $A^2/O$ process with fixed film was developed in this work and the characteristics of denitrification were especially investigated in the combined fixed film reactor(CFFR). Media was added in the anaerobic, anoxic and aerobic reactors, respectively. Tests were made to establish the effluent level of $NO_x-N$, COD, DO and nitrite effects on $NO_x-N$ removal in the CFFR by decreasing hydraulic retention time (HRT) from 10.0 to 3.5 hours and by increasing internal recycle ratio form 0% to 200%. The influent was synthesized to levels similar to the average influent of municipal wastewater treatment plants in Korea. SARAN media with a porosity of 96.3% was packed 40% / 130% / 25% based on its reactor volume, respectively. It was found that COD rarely limited dentrification in the anoxic reactor because of high $C/NO_x/-N$ ratio in the anoxic reactor, while DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent inhibited denitrification in the anoxic reactor. It was proved that the critical points of DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent were 0.15mg/L and 10%, respectively. As the internal recycle ratio increased, DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent increased. Especially, at the condition of internal recycle ratio, 200%, DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent exceeded the critical points of 0.15mg/L and 10%, respectively. Then, denitrification efficiency considerably decreased. Consequently, it was represented that the control of DO concentration in the anoxic reactor and $NO_2-N/NO_x/-N$ from the aerobic effluent can assure effective denitrification.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.1-8
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• 2015

When the line and switchgear of the substation system are disconnected, ferro-resonance can occur. This happens even if the capacitive reactance and inductive reactance are not equal, which are not common resonance conditions. Resonance conditions vary depending on the busbar configuration environment. Although the damping resistance method applying the existing saturable reactor to cope with ferro-resonance has been successfully applied on site, there can be loss of normal function during long-term operation. The reason is because the rise in the operating frequency of saturable reactors means the saturation number is increased. Therefore, it can no longer function as saturable reactor since the resistor having inadequate capacity is burned out. To address this problem, in this paper, an EMTP-based simulation test was performed by designing and applying a dual reactor method, which adds an extended divergence reactor to the 1st side of the VT. The test result confirms that when the divergence reactor is inserted, the voltage and current values obtained at the 1st side and 2nd side of the VT as well as current values of divergence reactor part were stabilized from the transient phenomena and return to normal values. When compared with existing measures, although this method is similar in adding having a reactor added to a system regarding ferro-resonance, it has the advantage of being able to prevent ferro-resonance in advance since the reactor is added before the system is saturated. In addition, because it does not use damping resistance, it can extend the equipment life and stabilize its operation. Therefore, there are a lot of differences in terms of its operating characteristics and achivement of goal between the conventional method and new divergence reactor method.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1165-1203
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• 2024

In the paper we validate theoretical models of the pulse against experimental data from the Jozef Stefan Institute TRIGA Mark II research reactor. Data from all pulse experiments since 1991 have been collected, analysed and are publicly available. This paper summarizes the validation study, which is focused on the comparison between experimental values, theoretical predictions (Fuchs-Hansen and Nordheim-Fuchs models) and calculation using computational program Improved Pulse Model. The results show that the theoretical models predicts higher maximum power but lower total released energy, full width at half maximum and the time when the maximum power is reached is shorter, compared to Improved Pulse Model. We evaluate the uncertainties in pulse physical parameters (maximum power, total released energy and full width at half maximum) due to uncertainties in reactor physical parameters (inserted reactivity, delayed neutron fraction, prompt neutron lifetime and effective temperature reactivity coefficient of fuel). It is found that taking into account overestimated correlation of reactor physical parameters does not significantly affect the estimated uncertainties of pulse physical parameters. The relative uncertainties of pulse physical parameters decrease with increasing inserted reactivity. If all reactor physical parameters feature an uncorrelated uncertainty of 10 % the estimated total uncertainty in peak pulse power at 3 $ inserted reactivity is 59 %, where significant contributions come from uncertainties in prompt neutron lifetime and effective temperature reactivity coefficient of fuel. In addition we analyse contribution of two physical mechanisms (Doppler broadening of resonances and neutron spectrum shift) that contribute to the temperature reactivity coefficient of fuel. The Doppler effect contributes around 30 %-15 % while the rest is due to the thermal spectrum hardening for a temperature range between 300 K and 800 K.

• 환경위생공학
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• 제14권3호
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• pp.130-138
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• 1999

The feasibility of municipal sewage sludge digestion was investigated by using thermophilic anaerobic sequencing batch reactor(ASBR). One-day settle time was enough for the high performance of solid-liquid separation. The conversion of semi-continuous mode to sequencing batch mode is easily achieved without any adverse effects, although the large amount of sludge equal to the volume ratio of 0.3~06 to reactor volume was added in the feed step of the start-up. The ASBRs had higher conversion capability of organics to biogas than the control reactor. Gas yields of the ASBRs were increased by the average of 50% over the control reactor across a range of hydraulic retention time(HRT)s from 10days to 5days. The thermophilic reactors showed higher gas production than mesophilic reactor. Removal efficiencies of organic matter exceeded 80% on the basis of supernatants, except that at the reactor. Solid-liquid separation was essential in the performance of the ASBR, especially, at the lower HFT. The ASBRs were highly efficient in the retention of activated biomass within the reactor. thus compensating for increased equivalent organic loading rate through increased solids retention times followed by the increased solids, while maintaining shorter HRTs.

• International Journal of Safety
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• 제7권2호
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• pp.7-11
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• 2008

In this paper, a Magnetic Core Reactor (MCR) which forms a part of the DC reactor type three-phase high-Tc superconducting fault current limiter (SFCL) has been developed. This SFCL is more economical than other types with three coils since it uses only one high-Tc superconducting (HTS) coil. When DC reactor type three-phase high-Tc SFCL is developed using just one coil, fewer power electronic devices and shorter HTS wire are needed. The SFCL proposed in this paper needs a power-linking device to connect the SFCL to the power system. The design concept for this device was sprang from the fact that the magnetic energy could be changed into the electrical energy and vice versa. Ferromagnetic material is used as a path of magnetic flux. When high-Tc superconducting DC reactor is separated from the power system by using SCRs, this device also limits fault current until the circuit breaker is opened. The device mentioned above was named Magnetic Core Reactor (MCR). MCR was designed to minimize the voltage drop and total losses. Majority of the design parameters was tuned through experiments with the design prototype. In the experiment, the current density of winding conductor was found to be $1.3\;A/mm^2$, voltage drop across MCR was 20 V and total losses on normal state was 1.3 kW.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.15-19
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• 2014

A Failure or degradation of reactor upper head penetration is a recurring problem due to long term operation at nuclear power plants. And a flaw in the reactor upper head penetration has caused unplanned plant shutdown for repair as well as high economic impact on the plants. Consequently, a detection of flaws is of the utmost importance. Prior to the replacement of reactor upper head penetration, some utilities have repaired the flaws of reactor upper head penetration generated by overlay weld. Until now, only the base metal in reactor upper head penetration has been inspected according to 10 CFR 50.55a and ASME code case N-729-1. Accordingly, it is difficult to detect manufacturing defects and repair defects in overlay weld. This paper presents a case study on the application of Time of Flight Diffraction technique for reactor head penetration mockup with artificial flaws in overlay weld. This study offers a way to understand the flaws detected in reactor upper head penetration overlay weld.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.30-35
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• 2000

The pulsed plasma wire-plate reactor was analyzed on the basis of experiment, EMTP simulation and modelling method. Though the reactor has a non-linear impedance characteristics, we demonstrate that the reactor impedance can be approximately analyzed with the measured initial capacitance and average resistive component of flat zone. Using this modelling method, the influence of the reactor capacitance on the impedance matching between pulse generator and reactor can be investigated. From this, we found that the energy of 95% was delivered form pulse generator to reactor at the ratio of $C_r/C_p\cong 0.3,\; where\; C_p\; is\; pulse\; generator\; capacitance, C_r$ is reactor capacitance.