• Nuclear Engineering and Technology
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• 제21권1호
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• pp.1-11
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• 1989

원자로 정지동안에도, 잔열제거계통은 그 기능이 계속 유지되어야 하나, 실제로 가압 경수로에서 냉각상실고가 많이 발생되어 있다. 본 논문은 원자로 정지중의 냉각기능상실을 예방하고, 또한 냉각기능상실로 인한 노심손상의 중대성을 완화시키기 위한 대책을 강구하기 위한 시도로서, 전형적인 가압경수로에 대한 사고/고장 수목과 운전원실수 확률을 위한 HCR 모델, 초기 사상의 빈도를 위한 2단계 bayesian 방법 및 고장난 계통의 회복 활률을 위한 계단함수 모델 등을 이용한 원자로 정지 위해도 모델을 개발하여, 잔열제거계통의 신뢰도를 분석하였다. 그 결과는 원자로가 정지 중일 때의 위해도가 운전중일 때 이것에 비해 별로 낮지 않은 것으로 나타났으며, 몇 가지의 설계개선을 통하여 냉각기능상실로 인한 노심 손상확률을 상당히 낮출 수 있는 것으로 나타났다.

• Safety and Health at Work
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• 제9권1호
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• pp.42-52
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• 2018

Background: Maintenance operations on-board ships are highly demanding. Maintenance operations are intensive activities requiring high man-machine interactions in challenging and evolving conditions. The evolving conditions are weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress. For example, extreme weather condition affects seafarers' performance, increasing the chances of error, and, consequently, can cause injuries or fatalities to personnel. An effective human error probability model is required to better manage maintenance on-board ships. The developed model would assist in developing and maintaining effective risk management protocols. Thus, the objective of this study is to develop a human error probability model considering various internal and external factors affecting seafarers' performance. Methods: The human error probability model is developed using probability theory applied to Bayesian network. The model is tested using the data received through the developed questionnaire survey of >200 experienced seafarers with >5 years of experience. The model developed in this study is used to find out the reliability of human performance on particular maintenance activities. Results: The developed methodology is tested on the maintenance of marine engine's cooling water pump for engine department and anchor windlass for deck department. In the considered case studies, human error probabilities are estimated in various scenarios and the results are compared between the scenarios and the different seafarer categories. The results of the case studies for both departments are also compared. Conclusion: The developed model is effective in assessing human error probabilities. These probabilities would get dynamically updated as and when new information is available on changes in either internal (i.e., training, experience, and fatigue) or external (i.e., environmental and operational conditions such as weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress) factors.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.583-592
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• 2011

The radiological characteristics for waste classification were assessed for neutron-activated decommissioning wastes from a CANDU reactor. The MCNP/ORIGEN2 code system was used for the source term analysis. The neutron flux and activation cross-section library for each structural component generated by MCNP simulation were used in the radionuclide buildup calculation in ORIGEN2. The specific activities of the relevant radionuclides in the activated metal waste were compared with the specified limits of the specific activities listed in the Korean standard and 10 CFR 61. The time-average full-core model of Wolsong Unit 1 was used as the neutron source for activation of in-core and ex-core structural components. The approximated levels of the neutron flux and cross-section, irradiated fuel composition, and a geometry simplification revealing good reliability in a previous study were used in the source term calculation as well. The results revealed the radioactivity, decay heat, hazard index, mass, and solid volume for the activated decommissioning waste to be $1.04{\times}10^{16}$ Bq, $2.09{\times}10^3$ W, $5.31{\times}10^{14}\;m^3$-water, $4.69{\times}10^5$ kg, and $7.38{\times}10^1\;m^3$, respectively. According to both Korean and US standards, the activated waste of the pressure tubes, calandria tubes, reactivity devices, and reactivity device supporters was greater than Class C, which should be disposed of in a deep geological disposal repository, whereas the side structural components were classified as low- and intermediate-level waste, which can be disposed of in a land disposal repository. Finally, this study confirmed that, regardless of the cooling time of the waste, 15% of the decommissioning waste cannot be disposed of in a land disposal repository. It is expected that the source terms and waste classification evaluated through this study can be widely used to establish a decommissioning/disposal strategy and fuel cycle analysis for CANDU reactors.

• 한국재료학회지
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• 제19권6호
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• pp.305-312
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• 2009

The effects of Quenching and Partitioning (Q&P) and Annealed Martensite (AM) heat treatment on the microstructure and tensile properties were investigated for 0.24C-0.5Si-1.5Mn-1Al steels. The Q&P steels were annealed at a single phase ($\gamma$) or a dual phase (${\gamma}+{\alpha}$), followed by quenching to a temperature between $M_s$ and $M_f$. Then, enriching carbon was conducted to stabilize the austenite through the partitioning, followed by water quenching. The AM steels were intercritically annealed at a dual phase (${\gamma}+{\alpha}$) temperature and austempered at $M_s$ and $M_s{\pm}50^{\circ}C$, followed by cooling in oil quenching. The dual phase Q&P steels showed lower tensile strength and yieldyield strength than those of the single phase Q&P steels, and tThe elongation for the dual phase Q&P steel was partitioning 100s higher than that of that for the single phase Q&P steels as the partitioning time was less than 100s up to partitioning 100s. For AM steels, the tensile/yield strength decreased and the total elongation increased as the austempering temperature increased. The stability of the retained austenite controlled the elongation for Q&P steels and the volume fraction of the retained austenite controlled the elongation for AM steels.

• ALGAE
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• 제28권2호
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• pp.173-183
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• 2013

Sodium hypochlorite (NaOCl) is widely used to disinfect seawater in power plant cooling systems in order to reduce biofouling, and in ballast water treatment systems to prevent transport of exotic marine species. While the toxicity of NaOCl is expected to increase by ongoing ocean acidification, and many experimental studies have shown how algal calcification, photosynthesis and growth respond to ocean acidification, no studies have investigated the relationship between NaOCl toxicity and increased $CO_2$. Therefore, we investigated whether the impacts of NaOCl on survival, chlorophyll a (Chl-a), and effective quantum yield in three marine phytoplankton belonging to different taxonomic classes are increased under high $CO_2$ levels. Our results show that all biological parameters of the three species decreased under increasing NaOCl concentration, but increasing $CO_2$ concentration alone (from 450 to 715 ${\mu}atm$) had no effect on any of these parameters in the organisms. However, due to the synergistic effects between NaOCl and $CO_2$, the survival and Chl-a content in two of the species, Thalassiosira eccentrica and Heterosigma akashiwo, were significantly reduced under high $CO_2$ when NaOCl was also elevated. The results show that combined exposure to high $CO_2$ and NaOCl results in increasing toxicity of NaOCl in some marine phytoplankton. Consequently, greater caution with use of NaOCl will be required, as its use is widespread in coastal waters.

• 한국정밀공학회지
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• 제33권5호
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• pp.393-400
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• 2016

High frequency induction heating (HFIH) is used in many industries and has a number of advantages, including reliability and repeatability. It is a non-contact method of providing energy-efficient heat in the minimum amount of time without using a flame. Recently, HFIH has been actively studied using the finite element method (FEM), however, these studies only focused on the accuracy of the analysis. In this paper, we can measure joule heat distributions by the electromagnetic analysis for HFIH and the temperature distribution from the heat transfer analysis by applying joule heat for a sprocket. The sprocket is heated over $850^{\circ}C$ due to joule heat and then cooled to under $200^{\circ}C$ by using cooling $20^{\circ}C$ water. These processes were used to calculate the FEM and then compared to our experimental results. The calculated outcome may be used to predict hardening depth in HFIH.

• Journal of the korean society of oceanography
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• 제39권4호
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• pp.234-242
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• 2004

The pigment composition and concentration of phytoplankton assemblages using HPLC in the adjacent waters of four nuclear power plants (Yonggwang, Kori, Wolsong and Ulchin) were investigated during the spring blooming in 2004. The mean concentration of chlorophyll a ranged from 563.8 to 2,949.0ng $l^{-1}$, with the lowest concentration at Kori and the highest concentration at Wolsong. Among the carotenoids, the amounts of fucoxanthin and chlorophyll $C_2$ were relatively higher than those of other pigments in the study site. As minor pigments, zeaxanthin, chlorophyll b, 19'-butanoyloxyfucoxanthin, diadinoxanthin, 19'-hexanoyloxyfucoxanthin, chlorophyll $C_3$ and peridinin were detected. The results of pigment composition and concentration showed that diatoms had an important proportion of phytoplankton community when a spring bloom occurred. Cyanobacteria was present relatively low density at the Wolsong and the green alga such as chlorophytes and prasinophytes were abundant at the Yonggwang and Kori, while dinoflagellates characterized by peridinin were common at Ulchin and Kori. The pigment composition and concentration of phytoplankton after passing through the cooling-water system of nuclear power plant were highly variable. No distinct trend of the change of each pigment composition and amount was detected but the variation of fucoxanthin and chlorophyll $C_2$ highly coupled with that of chlorophyll a. We pointed out that the diatom controlled the overall variation of phytoplankton biomass during the spring season.

• 한국식품과학회지
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• 제49권4호
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• pp.401-407
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• 2017

볶은 미강을 첨가하여 제조한 식빵의 부피 및 비부피, 굽기 및 냉각 손실률, 총산도, 수분활성도, 색도, 조직감, 관능검사 등을 조사하였다. 식빵의 품질 특성 결과에서 식빵의 부피 및 비부피는 볶은 미강 첨가량이 증가할수록 다소 감소하였다. 식빵의 굽기와 냉각 손실률은 볶은 미강 첨가량이 증가할수록 감소하였다. 볶은 미강 첨가량이 증가할수록 식빵의 pH는 낮아지고 총산도는 증가하였다. 수분함량과 수분활성도는 볶은 미강 첨가량이 증가할수록 높아지는 경향을 보였다. Crust와 crumb 색도 변화는 볶은 미강 첨가량이 증가할수록 명도 L값은 낮아졌으며, 적색도 a값과 황색도 b값은 증가하였다. 볶은 미강 첨가량이 증가할수록 경도(hardness), 탄력성(springiness), 점착성(gumminess)은 증가하였고, 응집성(cohesiveness)은 감소하였다. 식빵의 관능검사 결과 향, 맛, 전반적인 기호도는 볶은 미강을 5%첨가하여 제조한 식빵이 대조구에 비해 같거나 다소 높았으며, 15% 첨가구는 낮았다. 이상의 연구로 식빵 제조시 볶은 미강 5% 첨가는 제품의 특성에 좋지 않은 영향을 미치지 않았으며 전반적인 기호도가 높아 기능성 빵으로의 개발 가능성이 있는 것으로 생각된다.

• 한국가스학회지
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• 제2권1호
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• pp.14-22
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• 1998

본 연구에서는 LNG 저장탱크에서 액면화재(pool fire) 발생시 복사열속(radiation flux)의 정량적인 예측과 복사열 피해를 줄이는 방법을 제안하기 위하여 RISC모델을 사용하여 여러 조건에서 복사열속을 계산하였다. 모델 예측결과 LNG 탱크의 액면화재에 의한 복사열 피해에 가장 큰 영향을 미치는 인자는 풍속임을 알 수 있었다. 화염과 피해 대상물사이의 복사피해 정도는 높은 풍속에서 보다 낮은 풍속에서의 풍속변화에 따라 크게 변하였다. 또한 액면화재 발생시 복사열 피해는 탱크 또는 공장 주위에 방풍시설을 함으로써 크게 줄일 수 있음을 알 수 있었다. 방풍시설은 다른 방법들 보다 경제적이기 때문에 냉각시설 및 소방시설과 연계하여 가스 저장탱크 주위에 설치하는 것이 바람직하다.

• 한국정보통신학회논문지
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• 제11권5호
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• pp.1013-1018
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• 2007

자동차의 연료분사에 관여하는 전자제어 센서에는 공기유량 센서, 흡기온도 센서, 대기압 센서, 냉각수 온도센서, 스로틀 포지션 센서, 모터 포지션 센서 등이 있다. 본 논문에서는 흡기온도 센서의 온도 변화와 공기와 연료의 혼합비율인 공연비에 대해 퍼지 제어 기법을 적용하여 차량의 연료 소비를 제어하는 방법을 제안하였다. 제안된 기법에서는 각각의 공기 유입량과 연료 분사량을 이용하여 공연비 수치를 구한 후, 공연비, 흡기온도, 최종 연료 보정량에 대해 설정된 퍼지 소속 함수와 퍼지 추론 규칙에 따라 차량 연료가 제어된다. 제어하는 방법을 제시하였다. 시뮬레이션을 통한 일반적인 차량의 연료 제어 방법과 비교 분석한 결과, 제안된 방법이 차량의 연료제어에 있어 효과적임을 확인하였다.