• 상하수도학회지
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• 제31권6호
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• pp.539-549
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• 2017

In water treatment process using microfiltration membranes, manganese is a substance that causes inorganic membrane fouling. As a result of analysis on the operation data taken from I WTP(Water Treatment Plant), it was confirmed that the increase of TMP was very severe during the period of manganese inflow. The membrane fouling fastened the increase of TMP and shortened the service time of filtration or the cleaning cycle. The TMP of the membrane increased to the maximum of $2.13kgf/cm^2$, but it was recovered to the initial level ($0.17kgf/cm^2$) by the 1st acid cleaning step. It was obvious that the main membrane fouling contaminants are due to inorganic substances. As a result of the analysis on the chemical waste, the concentrations of aluminum(146-164 mg/L) and manganese(110-126 mg/L) were very high. It is considered that aluminum was due to the residual unreacted during coagulation step as a pretreatment process. And manganese is thought to be due to the adsorption on the membrane surface as an adsorbate in feed water component during filtration step. For the efficient maintenance of the membrane filtration facilities, optimization of chemical concentration and CIP conditions is very important when finding the abnormal level of influent including foulants such as manganese.

• Nuclear Engineering and Technology
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• 제45권6호
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• pp.731-744
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• 2013

Energy security is a topic of high importance to many countries throughout the world. Countries with access to vast energy supplies enjoy all of the economic and political benefits that come with controlling a highly sought after commodity. Given the desire to diversify away from fossil fuels due to rising environmental and economic concerns, there are limited technology options available for baseload electricity generation. Further complicating this issue is the desire for energy sources to be sustainable and globally scalable in addition to being economic and environmentally benign. Nuclear energy in its current form meets many but not all of these attributes. In order to address these limitations, TerraPower, LLC has developed the Traveling Wave Reactor (TWR) which is a near-term deployable and truly sustainable energy solution that is globally scalable for the indefinite future. The fast neutron spectrum allows up to a ~30-fold gain in fuel utilization efficiency when compared to conventional light water reactors utilizing enriched fuel. When compared to other fast reactors, TWRs represent the lowest cost alternative to enjoy the energy security benefits of an advanced nuclear fuel cycle without the associated proliferation concerns of chemical reprocessing. On a country level, this represents a significant savings in the energy generation infrastructure for several reasons 1) no reprocessing plants need to be built, 2) a reduced number of enrichment plants need to be built, 3) reduced waste production results in a lower repository capacity requirement and reduced waste transportation costs and 4) less uranium ore needs to be mined or purchased since natural or depleted uranium can be used directly as fuel. With advanced technological development and added cost, TWRs are also capable of reusing both their own used fuel and used fuel from LWRs, thereby eliminating the need for enrichment in the longer term and reducing the overall societal waste burden. This paper describes the origins and current status of the TWR development program at TerraPower, LLC. Some of the areas covered include the key TWR design challenges and brief descriptions of TWR-Prototype (TWR-P) reactor. Selected information on the TWR-P core designs are also provided in the areas of neutronic, thermal hydraulic and fuel performance. The TWR-P plant design is also described in such areas as; system design descriptions, mechanical design, and safety performance.

• 에너지공학
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• 제6권1호
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• pp.87-95
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• 1997

금속염화물과 암모니아간의 가역반응을 이용한 화학열펌프는 비프레온계 냉동 냉장시스템으로서 환경규약의 제한이 없고 가스, 전기 및 산업폐열 등 다양한 구동열원을 사용할수 있으며 축열에 의한 에너지 저장이나 산업공정에서의 대용량 에너지관리 시스템 등 응용분야가 다양한 장점을 갖고 있다. 통상 소규모의 실험실 장치에서 파일롯트 플랜트(pilot plant)로 전환하는 과정에서 시스템의 성능에 대한 해석이 필요하며 화학반응기의 거동에 대한 컴퓨터 모사도 필수적이다. 따라서 본 연구에서는 작동조건에 따라 화학식 냉동기 성능계수가 어떻게 변하는지를 예측하였고 반응기 모델링에 의한 동적모사를 수행하여 반응기의 온도거동, 작동조건에 따른 전화율 변화, 반응혼합물의 제조변수가 냉동기 성능에 미치는 영향 등을 고찰하였다.

• 방사성폐기물학회지
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• 제5권1호
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• pp.65-78
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• 2007

지하 동굴식 처분장의 건설, 운영 및 중-저준위 방사성폐기물을 처분한 이후 발생하게 되는 오염물질(Rn, CH CO, HS, Radiolysis에 의한 방사능 가스 등)은 적절한 공기량을 필요로 한 곳에 정확히 분배시킬 수 있는 환기시스템에 의해 통제되도록 하여야한다. 특히 지하 처분장은 여러 개의 진입 터널, 저장 터널, 공기 유입-배기 터널, 수직갱 등으로 이루어진 복잡한 회로망의 형태로 나타나기 때문에 이에 적절한 기술적 접근이 필요하다. 본 논문에서는 이러한 환기시스템 구축을 위한 기술적 접근을 위해 미국의 WIPP (Waste Isolation Pilot Plant)처분장과 스웨덴의 SFR (Slutforvar for Reaktoravfall) 중-저준위 처분장을 모델로 하여 두 처분장의 소요환기량을 선정하고 설계상 통풍로의 단면적, 길이, 표면 거칠기 등을 고려한 환기회로를 구성하였으며, 수학적으로 계산되는 각 회로의 저항에 대해 기술하였다. 또한 이를 바탕으로 적절한 선풍기의 용량과 수직갱 운용방안을 설계하였다. 두 처분장의 지형상의 규모 및 환기시설 비교 결과, SFR 처분장에 비해 WIPP 처분장에서와 같이 병렬구조가 많을수록 처분장 전체의 저항이 감소되며 이러한 결과로 환기시스템의 운용비 절감효과를 얻을 수 있다는 결론을 얻었다. 따라서 처분용량 증대를 위한 대단면의 SFR 처분장 구조와 전체 저항 감소를 위한 WIPP 처분장의 병렬구조를 조합한 형태가 가장 합리적이며 효율적인 환기가 이루어질 수 있을 것으로 사료된다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 Proceedings of the 4th Korea-China Joint Workshop on Nuclear Waste Management
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• pp.140-142
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• 2004

Since the April of 1978, Korea has strongly relied on the nuclear energy for electricity generation. As of today, eighteen nuclear power plants are in operation and ten are to be inaugurated by 2015. The installed nuclear capacity is 15, 716 MW as of the end of 2002, representing 29.3% of the nation's total installed capacity. The nuclear share in electricity remains around 38.9 at the end of 2002, reaching at the level of 119 billion kWh's. New power reactors, KSNP's (Korea Standard Nuclear Power Plant) are fully based on the domestic technologies. More advanced reactors such as KNGR (Korea Next Generation Reactor) will be commercialized soon. Even though the front end nuclear cycle enjoys one of the best positions in the world, there have been some chronical problems in the back end fuel cycle. That's the one of the reason why we need more active R&D programs in Korea and active international and regional cooperation in this area. The everlasting NIMBY problem hinders the implementation of the nation's radioactive waste management program. We expect that the storage capacity for the LILW(Low and Intermediate Level radioactive Waste) will be dried out soon. The situation for the spent fuel storage is also not so favorable too. The storage pools for spent fuel are being filled rapidly so that in 2008, some AR pools cannot accommodate any more new spent nuclear fuels. The Korean Government in strong association with utilities and national academic and R&D institutes have tried its best effort to secure the site for a LILW repository and a AFR site. Finally, one local community, Buan in Jeonbook Province, submitted the petition for the site. At the end of the last July, the Government announced that the Wido, a small island in Buan, is suitable for the national complex site. The special force team headed by Dr IS Chang, president of KAERI teamed with Government officials and many prominent scholars and journalists agreed that by the evidences from the preliminary site investigation, they could not find any reason for rejecting the local community's offer.

• Journal of Radiation Protection and Research
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• 제45권4호
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• pp.178-186
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• 2020

Background: Reactor pressure vessel (RV) with internals (RVI) are activated structures by neutron irradiation and volume contaminated wastes. Thus, to develop safe and optimized disposal plan for them at a disposal site, it is important to perform exact activation calculation and evaluate the dose rate on the surface of casks which contain cut-off pieces. Materials and Methods: RV and RVI are subjected to neutron activation calculation via Monte Carlo methodology with MCNP6 and ORIGEN-S program-neutron flux, isotopic specific activity, and gamma spectrum calculation on each component of RV and RVI, and dose rate evaluation with MCNP6. Results and Discussion: Through neutron activation analysis, dose rate is evaluated for the casks containing cut-off pieces produced from decommissioned RV and RVI. For RV cut-off ones, the highest value of dose rate on the surface of cask is 6.97 × 10-1 mSv/hr and 2 m from it is 3.03 × 10-2 mSv/hr. For RVI cut-off ones, on the surface of it is 0.166 × 10-1 mSv/hr and 2 m from it is 1.04 × 10-1 mSv/hr. Dose rates for various RV and RVI cut-off pieces distributed lower than the limit except the one of 2 m from the cask surface of RVI. It needs to adjust contents in cask which carries highly radioactive components in order to decrease thickness of cask. Conclusion: Two types of casks are considered in this paper: box type for very-low-level waste (VLLW) as well as low-level waste (LLW) and cylinder type for intermediate-level waste (ILW). The results will contribute to the development of optimal loading plans for RV and RVI cut-off pieces during the decommissioning of nuclear power plant that can be used to prepare radioactive waste disposal plans for the different types of wastes-ILW, LLW, and VLLW.

• 한국항해항만학회지
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• 제47권2호
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• pp.106-119
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• 2023

Due to global decarbonization movement and tightening of maritime emissions restrictions, the shipping industry is going to switch to alternative fuels. Among candidates of alternative fuel, methanol is promising for decreasing SOx and CO2 emissions, resulting in minimum climate change and meeting the goal of green shipping. In this study, a novel combined system of direct methanol solid oxide fuel cells (SOFC), proton exchange membrane fuel cells (PEMFC), gas turbine (GT), and organic Rankine cycle (ORC) targeted for marine vessels was proposed. The SOFC is the main power generator of the system, whereas the GT and PEMFC could recover waste heat from the SOFC to generate useful power and increase waste heat utilizing efficiency of the system. Thermodynamics model of the combined system and each component were established and analyzed. Energy and exergy efficiencies of subsystems and the entire system were estimated with participation of the first and second laws of thermodynamics. The energy and exergy efficiencies of the overall multigeneration system were estimated to be 76.2% and 30.3%, respectively. The combination of GT and PEMFC increased the energy efficiency by 18.91% compared to the SOFC stand-alone system. By changing the methanol distribution ratio from 0.05 to 0.4, energy and exergy efficiencies decreased by 15.49% and 5.41%, respectively. During the starting up and maneuvering period of vessels, a quick response from the power supply system and propulsion plant is necessary. Utilization of PEMFC coupled with SOFC has remarkable meaning and benefits.

• Advances in Energy Research
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• 제7권2호
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• pp.147-166
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• 2020

Industrial cooling towers are often ageing infrastructure that is expensive to maintain and operate. A novel approach is introduced in which a heat pump circuit is incorporated to reduce the load upon the towers by extracting low-grade energy from the stream sent to the towers and repurposing in on-site processing operations. To demonstrate the concept, a model was constructed, which uses industrial data on cooling towers linked to a smelter's sulphuric acid plant, to allow direct economic and environmental impact comparison between different heat recovery and repurposing scenarios. The model's results showed that implementing a heat pump system would significantly decrease annual operating costs and achieve a payback period of 3 years. In addition, overall CO₂ emissions could be reduced by 42% (430,000 kg/year) and a 5% heat load reduction on the cooling towers achieved. The concept is significant as the outcomes introduce a new way for energy intensive industrial sectors, such as mineral processing, to reduce energy consumption and improve long-term sustainable performance.

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 1979년도 춘계학술대회
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• pp.113.1-113
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• 1979

Each year, vast amount of agricultural crop residues are produced (about 60 percent of the total crop production), which have not been effectively utilized because they are bulky and lignocellulosic, thus having little fuel energy per unit volume. Using treated plant residues as animal feeds could result in an ultimate saving of fossil fuel energy and a more effective utilizat ion of products created by the photosynthetic process. Feeding the residues to animals would decrease the pollution potential, but these residues are difficult for even a ruminant animal to digest. If cellulosic wastes produced from cereal grain straw and wood could be digested, land now used for producing forage add grain cnuld be shifted to food crops for humans. During the past decade, considerable efforts were made to utilize crop residues. These utilization methods can be broadly grouped into for categories: (1) direct uses, (2) mechanical conversions, (3) chemical conversions and (4) biological conversions. Agricultural crop residues consist mainly of cellulose, hemicellulose, lignin, pectin, andother plant carbohydrates. The nature of the constituents of these residues can be best utilized as one of the five FS: Fuel, Fiber, Fertilizer, Feed and Food. Many processes have teen proposed and some are in industrial production stage. However, economics of the process depend on the location where availability of other competitive products are different.

• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.670-678
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• 1999

Heat recovery steam generator(HRSG) is a principal component of the combined cycle power plant (CCPP) which utilizes the waste energy of the gas turbine exhaust gas. A design of the HRSG is a keypoint to achieve high cycle efficiency with competitive cost. This paper presents a brief review on the design of a HRSG which covers the basic design parameters and their effects on the performance and the investment cost. Finally the concept of the optimum design point is presented according to the selection of a pinch point temperature difference and a steam pressure as an illustrated case.