• Nuclear Engineering and Technology
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• 제16권3호
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• pp.155-160
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• 1984

표준 핵연료집합체나 최적 핵연료집합체로 구성된 원자력 1호기 원자로심의 열적여유도를 기존 열설계 방법과 통계적 열설계 방법을 이용하여 분석하였다. 통계적 열설계 방법은 노심내 운전변수들의 불확실도를 통계적으로 처리함으로써 기존 방법에 비하여 열적여유도를 증가시킨다. 계산을 위하여 정상상태와 과도시 열수력분석 전산코드인 COBRA-IV-i를 사용하였다. 계산결과 통계적 설계방법은 열적여유도를 크게 증가시키며, 표준 핵 연료집 합체는 물론 최적 핵 연료집 합체가 장전된 원자력 1호기의 열설계기준을 만족시키는 것으로 밝혀졌다. 그러나 기존 열설계 방법은 원자력 1호기 노심에 최적 핵연료집합체가 장전된 경우 열설계기준을 만족시키지 못하는 것으로 밝혀졌다.

• 한국물환경학회지
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• 제37권1호
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• pp.47-54
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• 2021

Aerobic granular sludge (AGS) can be classified as a type of self-immobilized microbial aggregates measuring more than 0.2 mm. It offers the option to simultaneously remove COD, N, and P that occur in different zones inside a granule. Also, AGS is characterized by high precipitability, treatability with high organic loading, and high tolerance to low temperature. In this study, a sequencing batch reactor inoculated with AGS (AGS-SBR) is a new advanced wastewater treatment process that was proven to grow AGS with integrated nutrient removal and low C/N ratio. A pilot plant, AGS-SBR with a capacity of 225 ㎥/d was installed at an S sewage treatment plant in Gyeonggi-do. The results of the operation showed that the water quality of the effluent indicated that the value of BOD5 was 1.5 mg/L, CODMn was 11.4 mg/L, SS was 6.2 mg/L, T-N was 13.2 mg/L, and T-P was 0.197 mg/L, and all of these values reliably satisfied an effluent standard (I Area). In winter, the T-N treatment efficiency at a lower temperature of less than 11℃ also showed reliability to meet the effluent standard of the I Area (20 mg/L or less). Analysis of microbial community in AGS showed a higher preponderance of beneficial microorganisms involved in denitrification and phosphorus accumulation compared with activated sludge. The power consumption and sludge disposal cost were reduced by 34.7% and 54.9%, respectively, compared to the domestic SBR type sewage treatment plant with a processing capacity of 1,000 ㎥/d or less.

• Nuclear Engineering and Technology
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• 제36권3호
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• pp.248-262
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• 2004

Turbulence models are separately assessed for a three dimensional thermal-hydraulic analysis of the integral reactor SMART. Seven models (mixing length, k-l, standard $k-{\epsilon},\;k-{\epsilon}-f{\mu},\;k-{\epsilon}-v2$, RRSM, and ERRSM) are investigated for flat plate channel flow, rotating channel flow, and square sectioned U-bend duct flow. The results of these models are compared to the DNS data and experiment data. The results are assessed in terms of many aspects such as economical efficiency, accuracy, theorization, and applicability. The standard $k-{\epsilon}$ model (high Reynolds model), the $k-{\epsilon}-v2$ model, and the ERRSM (low Reynolds models) are selected from the assessment results. The standard $k-{\epsilon}$ model using small grid numbers predicts the channel flow with higher accuracy in comparison with the other eddy viscosity models in the logarithmic layer. The elliptic-relaxation type models, $k-{\epsilon}-v2$, and ERRSM have the advantage of application to complex geometries and show good prediction for near wall flows.

• 전기학회논문지
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• 제57권6호
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• pp.938-943
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• 2008

Coupling capacitor voltage transformers(CCVTs) have been used in extra or ultra high voltage systems to obtain the standard low voltage signal for protection and measurement. For fast suppression of the phenomenon of ferroresonance, three winding CCVTs are used instead of two winding CCVTs. A tuning reactor is connected between a capacitor voltage divider and a voltage transformer to reduce the phase angle difference between the primary and secondary voltages in the steady state. Slight distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has significant errors due to the transient components such as dc offset component and/or high frequency components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of a three winding CCVT in the time domain. With the values of the measured secondary voltage of the three winding CCVT, the secondary, tertiary and primary currents and voltages are estimated; then the voltages across the capacitor and the tuning reactor are calculated and then added to the measured voltage. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the three winding CCVT irrespective of the fault distance, the fault impedance and the fault inception angle as well as in the steady state.

• 전기학회논문지
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• 제57권6호
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• pp.909-914
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• 2008

A coupling capacitor voltage transformer(CCVT) is used in an extra or ultra high voltage system to obtain the standard low voltage signal for protection. To avoid the phase angle error between the primary and secondary voltages, a tuning reactor is connected between a capacitor and a voltage transformer. The inductance of the reactor is designed based on the power system frequency. If a fault occurs on the power system, the secondary voltage of the CCVT contains some errors due to a dc offset component and harmonic components resulting from the fault. The errors become severe in the case of a close-in fault. This paper proposes an algorithm for compensating the secondary voltage of a CCVT in the time-domain. From the measured secondary voltage of the CCVT, the secondary and primary currents are obtained; then the voltage across the capacitor and the inductor is calculated and then added to the measured secondary voltage to obtain the correct primary voltage. Test results indicate that the proposed algorithm can compensate the distorted secondary voltage of the CCVT irrespective of the fault distance, the fault inception angle, and the burden of the CCVT.

• Environmental Engineering Research
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• 제23권1호
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• pp.46-53
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• 2018

This study explores the environmentally innovative and low-impact technology, a zero food waste system (ZFWS) that utilizes food waste and converts it into composts or biofuels and curtails carbon emissions. The ZFWS not just achieves food waste reductions but recycles food waste into fertilizer. Based on a fermentation-extinction technique using bio wood chips, the ZFWS was employed in a field experiment of the system installed in a large-scale apartment complex, and the performance of the system was examined. The on-site ZFWS consisted of three primary parts: 1) a food waste slot into which food waste was injected; 2) a fermentation-extinction reactor where food waste was mixed with bio wood chips made up of complex enzyme and aseptic wood chips; and 3) deodorization equipment in which an ultraviolet and ozone photolysis method was employed. The field experiment showed that food waste injected into the ZFWS was reduced by 94%. Overall microbial activity of the food waste in the fermentation-extinction reactor was measured using adenosine tri-phosphate (ATP), and the degradation rate of organic compounds, referred to as volatile solids, increased with ATP concentration. The by-products generated from ZFWS comply with the national standard for organic fertilizer.

• 한국환경보건학회지
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• 제26권3호
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• pp.92-97
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• 2000

The treatment of the washout from small scale incinerator was performed physically, chemically and biologically. The results are as follows. 1. SS, FS removal efficiency of washout wastewater from incinerator was 67.4%, 37.4%, while SS, FS of sewage wastewater was removed 63.2% 35.4% respectively. 2. The optimal conditions for chemical coagulation turned out to be pH 7.5, alum(Al2O3 10%) 30ml/ι and polyelectrolyte(A-601P 0.1%) 4ml/ι. SS 86%, FS 89.5%, BOD 42.5% and CODMn, 63.5% was removed and the removal efficiency of some metals are shown as Pb 93.5%, Zn 86.5% and Fe 80.6%. The concentration of the effluent was SS 9mg/ι, BOD 98.4mg/ι, and CODMn 138.4mg/ι. 3. The removal efficiency in treating washout wastewater of incinerator through HBC-briquet media was getting higher with increasing HRT, and mixed wastewater with 1:1, 1:2 ratio could be met up to the standard limit with higher HRT than 12hr. Under the condition of 1:2 mix ratio and HRT 24 hr, removal efficiency of SS, BOD, CODMn, T-N and T-P was 92.1%, 90%, 87%, 48.2% and 48%, respectively, and the concentration of treated wastewater was SS 2.9 mg/ι, BOD 10.3mg/ι, CODMn 14.1mg/ι, T-N 11.6 mg/ι and T-P 1.3 mg/ι, respectively.

• Nuclear Engineering and Technology
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• 제21권4호
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• pp.245-258
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• 1989

열중성자로의 핵계산을 위한 69군 단면적 라이브러리를 생산하였다. 기본 평가핵자료로는 IAEA Nuclear Data Section에서 수집된 자료가, 그리고 이를 처리하여 군정수화 하는데는 NJOY코드가 이용되었다. 새로이 마련된 라이브러리의 유용성을 검증하기 위해 각기 산화우라늄과 금속 우라늄 연료로 구성된 임계실험치를 WIMS-KAERI 코드로 계산된 결과와 비교, 검토하였다. 총 88임계결과에 대해 평균 $K_{eff}$ 값 0.9997, 그리고 표준 편차 0.69%를 보였다. PWR 연료의 연소결과로 얻어진 우라늄과 플루토늄 생성량에 대한 평가에서도 전반적으로 좋은 결과를 얻었다.다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.160-168
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• 1995

This paper describes computational efforts on the various energy and environmental problems using Patankar's SIMPLE method. The specific problems included in this study are : pollutant and flammable material dispersions in open and confined areas, aerator-induced flow in a lake for DO(dissolved oxygen) concentration, primary clarifier for water and waste water treatment, hood ventilation in workplace, cyclone and LNG combustors and Dow chlorination reactor. A control-volume based finite-difference method is employed together with the power-law scheme. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, says SIMPLER and SIMPLEC. The Reynolds stresses are closed using the standard or the RNG $k-{\varepsilon}$ models. Turbulent reaction is modeled using two fast chemistry methods such as eddy breakup and conserved scalar models. Further, a nonequilibrium model is developed for the application of the chlorination process in the Dow reactor. Other important empirical models and physical insights appeared in this study are presented and discussed in a brief note. The computational method developed in this study is considered, in general, as a viable tool for the design and determination of the optimal condition of various engineering system of interest.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.660-672
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• 2016

In Part I of this paper, the two-temperature homogenized model for the fully ceramic microencapsulated fuel, in which tristructural isotropic particles are randomly dispersed in a fine lattice stochastic structure, was discussed. In this model, the fuel-kernel and silicon carbide matrix temperatures are distinguished. Moreover, the obtained temperature profiles are more realistic than those obtained using other models. Using the temperature-dependent thermal conductivities of uranium nitride and the silicon carbide matrix, temperature-dependent homogenized parameters were obtained. In Part II of the paper, coupled with the COREDAX code, a reactor core loaded by fully ceramic microencapsulated fuel in which tristructural isotropic particles are randomly dispersed in the fine lattice stochastic structure is analyzed via a two-temperature homogenized model at steady and transient states. The results are compared with those from harmonic- and volumetric-average thermal conductivity models; i.e., we compare $k_{eff}$ eigenvalues, power distributions, and temperature profiles in the hottest single channel at a steady state. At transient states, we compare total power, average energy deposition, and maximum temperatures in the hottest single channel obtained by the different thermal analysis models. The different thermal analysis models and the availability of fuel-kernel temperatures in the two-temperature homogenized model for Doppler temperature feedback lead to significant differences.