• Title, Summary, Keyword: PAFS

Search Result 18, Processing Time 0.103 seconds

SEPARATE AND INTEGRAL EFFECT TESTS FOR VALIDATION OF COOLING AND OPERATIONAL PERFORMANCE OF THE APR+ PASSIVE AUXILIARY FEEDWATER SYSTEM

  • Kang, Kyoung-Ho;Kim, Seok;Bae, Byoung-Uhn;Cho, Yun-Je;Park, Yu-Sun;Yun, Byoung-Jo
    • Nuclear Engineering and Technology
    • /
    • v.44 no.6
    • /
    • pp.597-610
    • /
    • 2012
  • The passive auxiliary feedwater system (PAFS) is one of the advanced safety features adopted in the APR+, which is intended to completely replace the conventional active auxiliary feedwater system. With an aim of validating the cooling and operational performance of PAFS, an experimental program is in progress at KAERI, which is composed of two kinds of tests; the separate effect test and the integral effect test. The separate effect test, PASCAL ($\underline{P}$AF$\underline{S}$ $\underline{C}$ondensing Heat Removal $\underline{A}$ssessment $\underline{L}$oop), is being performed to experimentally investigate the condensation heat transfer and natural convection phenomena in PAFS. A single, nearly-horizontal U-tube, whose dimensions are the same as the prototypic U-tube of the APR+ PAFS, is simulated in the PASCAL test. The PASCAL experimental result showed that the present design of PAFS satisfied the heat removal requirement for cooling down the reactor core during the anticipated accident transients. The integral effect test is in progress to confirm the operational performance of PAFS, coupled with the reactor coolant systems using the ATLAS facility. As the first integral effect test, an FLB (feedwater line break) accident was simulated for the APR+. From the integral effect test result, it could be concluded that the APR+ has the capability of coping with the hypothetical FLB accident by adopting PAFS and proper set-points of its operation.

Enhanced Production of Antifungal Substance(PAFS) Bioxynthesized by Pseudomonas aeruginosa and Examination of Its Physiological Characteristics in Fermentation (Pseudomonas aeruginosa에 의핸 생합성되는 향진균성물질(PAFS)의 생산성 증가 및 생산균주의 배양생리학적 특성 연구)

  • 박선옥;송성기;윤권상;정연호;이상종;정용섭;전계택
    • Microbiology and Biotechnology Letters
    • /
    • v.28 no.6
    • /
    • pp.341-348
    • /
    • 2000
  • Selection of high producer strain, optimization of production medium and cultivation in bioreactor system were carried out in order to produce an antifungal substance, PAFS in large amounts which sources and 41 kinds of nitrogen sources, a synthetic medium consisting of fructose(70 g/1) and ammonium sulfate (10g/l) and a complex medium including galactose(30g/l), fructose(20g/l) and cottonseed flour(35g/l) were determined as opti-mized media for PAFS production. In bioreactor studies examining physiological characteristics of the pro- ducer microorganism with the complex medium, typical pattern of diauxic growth was observed as demonstrated by the result that fructose was not used before almost exhaustion on readily utilizable carbon source, galactose. When galactose was supplemented additionally during the fermentation period. PAFS pro-ductivity did no increases any more, indicating that large portion of the added galactose was used for cell growth instead of biosynthesis of the secondary metabolite. It was deduced that PAFS production could be enhananced by employing fed-batch operation in order to overcome the apparent phenomenon of catabolite repression and /or inhibition.

  • PDF

Safety Analysis of APR+ PAFS for CDF Evaluation (노심손상빈도 평가를 위한 APR+ PAFS의 안전 해석)

  • Kang, Sang Hee;Moon, Ho Rim;Park, Young Seop
    • Journal of the Korean Society of Safety
    • /
    • v.28 no.3
    • /
    • pp.123-128
    • /
    • 2013
  • The Advanced Power Reactor Plus(APR+), which is a GEN III+ reactor based on the APR1400, is being developed in Korea. In order to enhance the safety of the APR+, a passive auxiliary feedwater system(PAFS) has been adopted in the APR+. The PAFS replaces the conventional active auxiliary feedwater system(AFWS) by introducing a natural driving force mechanism while maintaining the system function of cooling the primary side and removing the decay heat. As the PAFS completely replaces the conventional AFWS, it is required to verify the cooling capacity of PAFS for the core damage frequency(CDF) evaluation. For this reason, this paper discusses the cooling performance of the PAFS during transient accidents. The test case and scenarios were picked from the result of the sensitivity analysis in APR+ Probabilistic Safety Assessment(PSA). The analysis was performed by the best estimate thermal-hydraulic code, RELAP5/.MOD3.3. This study shows that the plant maintains the stable state without the core damages under the given test scenarios. The results of PSA considering this analysis' results shows that the CDF values are decreased. The analysis results can be used for more realistic and accurate performance of a PSA.

ASSESSMENT OF CONDENSATION HEAT TRANSFER MODEL TO EVALUATE PERFORMANCE OF THE PASSIVE AUXILIARY FEEDWATER SYSTEM

  • Cho, Yun-Je;Kim, Seok;Bae, Byoung-Uhn;Park, Yusun;Kang, Kyoung-Ho;Yun, Byong-Jo
    • Nuclear Engineering and Technology
    • /
    • v.45 no.6
    • /
    • pp.759-766
    • /
    • 2013
  • As passive safety features for nuclear power plants receive increasing attention, various studies have been conducted to develop safety systems for 3rd-generation (GEN-III) nuclear power plants that are driven by passive systems. The Passive Auxiliary Feedwater System (PAFS) is one of several passive safety systems being designed for the Advanced Power Reactor Plus (APR+), and extensive studies are being conducted to complete its design and to verify its feasibility. Because the PAFS removes decay heat from the reactor core under transient and accident conditions, it is necessary to evaluate the heat removal capability of the PAFS under hypothetical accident conditions. The heat removal capability of the PAFS is strongly dependent on the heat transfer at the condensate tube in Passive Condensation Heat Exchanger (PCHX). To evaluate the model of heat transfer coefficient for condensation, the Multi-dimensional Analysis of Reactor Safety (MARS) code is used to simulate the experimental results from PAFS Condensing Heat Removal Assessment Loop (PASCAL). The Shah model, a default model for condensation heat transfer coefficient in the MARS code, under-predicts the experimental data from the PASCAL. To improve the calculation result, The Thome model and the new version of the Shah model are implemented and compared with the experimental data.

Fermentation Studies on Pseudomonas aeruginosa Producing Antifungal Secondary Metabolite, PAFS. (항진균물질을 생합성하는 Pseudomonas aeruginosa의 배양생리적 특성 연구)

  • 송성기;윤권상;정용섭;전계택
    • Microbiology and Biotechnology Letters
    • /
    • v.32 no.1
    • /
    • pp.52-59
    • /
    • 2004
  • When both fructose and galactose were added to a production medium as carbon sources, the productivity of PAFS (Psedomonas Antifungal Substance) biosynthesized by Pseudomonas aeruginosa was observed to be reduced significantly due to the well-known phenomenon of catabolite repression. In order to overcome this phenomenon by use of fermentation bioprocess, fed-batch cultivation method was examined. In addition, a high producer mutant strain, AP-20 obtained by a rational screening method was tested for its productivity of PAFS in both batch and fed-batch fermentation processes. Notably fed-batch operation showed approximately 4 fold higher PAFS productivity than traditional batch operation process. It was appeared that galactose was utilized principally for the cell growth of Pseudomonas aeruginosa whereas large portion of fructose was used for the biosynthesis of PAFS. Furthermore it was observed that composition and feeding rate of production media should be optimized even in the fed-batch fermentation bioprocess. As an example, very slow feeding of carbon sources gave rather negative effect on the production of PAFS due to significant limitation of carbon and energy sources available for the producer microorganism.

Thermal-hydraulic study of air-cooled passive decay heat removal system for APR+ under extended station blackout

  • Kim, Do Yun;NO, Hee Cheon;Yoon, Ho Joon;Lim, Sang Gyu
    • Nuclear Engineering and Technology
    • /
    • v.51 no.1
    • /
    • pp.60-72
    • /
    • 2019
  • The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).

Performance analysis of the passive safety features of iPOWER under Fukushima-like accident conditions

  • Kang, Sang Hee;Lee, Sang Won;Kang, Hyun Gook
    • Nuclear Engineering and Technology
    • /
    • v.51 no.3
    • /
    • pp.676-682
    • /
    • 2019
  • After the Fukushima Daiichi accident, there has been an increasing preference for passive safety features in the nuclear power industry. Some passive safety systems require limited active components to trigger subsequent passive operation. Under very serious accident conditions, passive safety features could be rendered inoperable or damaged. This study evaluates (i) the performance and effectiveness of the passive safety features of iPOWER (innovative Power Reactor), and (ii) whether a severe accident condition could be reached if the passive safety systems are damaged, namely the case of heat exchanger tube rupture. Analysis results show that the reactor coolant system remains in the hot shutdown condition without operator actions or electricity for over 72 h when the passive auxiliary feedwater systems (PAFSs) are operable without damage. However, heat exchanger tube rupture in the PAFS leads to core damage after about 18 h. Such results demonstrate that, to enhance the safety of iPOWER, maintaining the integrity of the PAFS is critical, and therefore additional protections for PAFS are necessary. To improve the reliability of iPOWER, additional battery sets are necessary for the passive safety systems using limited active components for accident mitigation under such extreme circumstances.

Visualization Experiment for Nucleate Boiling Bubble Motion on a Horizontal Tube Heater Fabricated with Flexible Circuit Board (연성회로기판 기반 수평전열관 표면의 비등기포거동 가시화 실험 연구)

  • Kim, Jae Soon;Kim, Yu-Na;Park, Goon-Cherl;Cho, Hyoung Kyu
    • Journal of the Korean Society of Visualization
    • /
    • v.14 no.2
    • /
    • pp.52-60
    • /
    • 2016
  • The Passive Auxiliary Feedwater System(PAFS) is one of the advanced safety concepts adopted in the Advanced Power Reactor Plus(APR+). To validate the operational performance of the PAFS, detailed understanding of a boiling heat transfer on horizontal tube outside is of great importance. Especially, in the mechanistic boiling heat transfer model, it is important to visualize the phenomena but there are some limitations with conventional experimental approaches. In the present study, we devised a heater based on the Flexible Printed Circuit Board (FPCB) for a more comprehensive visualization and subsequently, a digital image processing technique for the bubble motion measurement was established. Using the measurement technique, important parameters of the nucleate boiling are analyzed.

Risk and Sensitivity Analysis during the Low Power and Shutdown Operation of the 1,500MW Advanced Power Reactor (1,500MW대형원전 정지/저출력 안전성향상을 위한 설계개선안 및 민감도 분석)

  • Moon, Ho Rim;Han, Deok Sung;Kim, Jae Kab;Lee, Sang Won;Lim, Hak Kyu
    • Transactions of the Korean Society of Pressure Vessels and Piping
    • /
    • v.15 no.1
    • /
    • pp.33-39
    • /
    • 2019
  • An 1,500MW advanced power reactor required the standard design approval by a Korean regulatory body in 2014. The reactor has been designed to have a 4-train independent safety concept and a passive auxiliary feedwater system (PAFS). The full power risk or core damage frequency (CDF) of 1,500MW advanced power reactor has been reduced more than that of APR1400. However, the risk during the low power and shutdown (LPSD) operation should be reduced because CDF of LPSD is about 4.7 times higher than that of internal full power. The purpose of paper is to analysis design alternatives to reduce risk during the LPSD. This paper suggests design alternatives to reduce risk and presents sensitivity analysis results.