• Title/Summary/Keyword: Reactor stability

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Thermal Stability Improvement of Liquid Fuel by Using Some Additives (첨가제를 이용한 액체연료의 열안정성 향상)

  • Park, Sun-Hee;Kim, Joong-Yeon;Chun, Byung-Hee;Han, Jeong-Sik;Jeong, Byung-Hun;Kim, Sung-Hyun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.11a
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    • pp.294-299
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    • 2010
  • Thermal stability of exo-tetrahydrodicyclopentadiene (exo-THDCP) were investigated in a batch-type reactor perfectly coated with quartz. The 1 ml liquid product, which was a sufficiently small amount so as not to affect the reaction pressure, was sampled at 90 min intervals during the reaction and determined by gas chromatography-mass spectrometry (GC-MS) to measure thermal decomposition products of exo-THDCP and specify mechanism for additives (thermal stabilizer). Hydrogen donors (thermal stabilizer) such as 1,2,3,4-tetrahydroquinoline (THQ), benzyl alcohol (BnOH) increased thermal stability of exo-THDCP. These materials donated hydrogen to radical of exo-THDCP produced after initiation of exo-THDCP to decrease activity of primary products of exo-THDCP.

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Characteristics of Redox Agent with Additive in Steam-Iron Process for the High Purity Hydrogen Production (고순도 수소 생성을 위한 SIP법에서 첨가제에 따른 환원 특성)

  • Jeon, Bup-Ju;Kim, Sun-Myung;Park, Ji-Hun
    • Journal of Hydrogen and New Energy
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    • v.22 no.3
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    • pp.340-348
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    • 2011
  • Effects of various inorganic-metal oxide (Zr, Zn, Si, Al and Ca as promoters and stabilizers) additive on the reduction rate of iron oxide and the composition of forming hydrogen using the steam-iron cycle operation was investigated. The reduction rate of redox agent with additive was determined from weight change by TGA. The changes of weight loss and reduction rate according to redox agent with various additive affected the hydrogen purity and cycle stability of the process. The cyclic micro reactor showed that hydrogen purity exceeding 95% could be obtained by the water splitting with Si/Fe, Zn/Fe, Zr/Fe redox agents. The redox agents with these elements had an affect on redox cycle stability as a good stabilizer for forming hydrogen by the steam-iron process.

Vibration Characteristics of a Nuclear Fuel Rod in Uniform Axial Flow (균일한 축방향 유동에 노출된 핵 연료봉의 진동특성 분석)

  • Jeon, Sang-Youn;Suh, Jung-Min;Kim, Kyu-Tae;Park, Nam-Gyu
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.11 s.116
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    • pp.1115-1123
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    • 2006
  • Nuclear fuel rods are exposed to axial flow in a reactor, and flow-induced-vibration due to the flow usually causes damage in the fuel rods. Thus a prior knowledge about dynamic behavior of a fuel rod exposed to the flow condition should be provided. This paper shows that dynamic characteristics of a nuclear fuel rod depend on axial flow velocity. Assuming small lateral displacement, the effects of uniform axial flow are investigated. The analytic results show that axial flow generally reduces fuel rod stiffness and raises its damping in normal condition. Also, the critical axial velocities which make the fuel rod behavior unstable were found. That is, solving generalized eigenvalue equation of the fuel rod dynamic system, the eigenvalues with positive real part are detected. Based on the simulation results, on the other hand, it turns out that the ordinary axial flow in nuclear reactors does not affect to stability of a nuclear fuel rod even in the conservative condition.

A Design of Optimal PI Controller of SVC System using Genetic Algorithms (유전 알고리즘을 이용한 SVC 계통의 최적 PI 제어기 설계)

  • Jeong, Hyeong-Hwan;Heo, Dong-Ryeol;Wang, Yong-Pil;Han, Gil-Man;Kim, Hae-Jae
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.49 no.5
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    • pp.212-219
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    • 2000
  • This paper deals with a systematic approach to GA-PI controller design for static VAR compensator(SVC) using genetic algorithms(GAs) which are search algorithms based on the mechanics of natural of natural selection and natural genetics, to improve system stability. A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. To verify the robustness of the proposed method, considered dynamic response of generator used deviation and generator terminal voltage by applying a power fluctuation and three-phase fault at heavy load, normal load and light load. Thus, we proved usefulness of GA-PI controller design to improve the stability of single machine-infinite bus with SVC system.

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Design of GA-LQ Controller in SVC for Power System Stability Improvement (전력시스템 안정도 향상을 위한 SVC용 GA-LQ 제어기 설계)

  • Hur, D.R.;Park, I.P.;Chung, M.K.;Chung, H.H.;Ahn, B.C.;Kim, H.J.
    • Proceedings of the KIEE Conference
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    • 2002.07a
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    • pp.226-228
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    • 2002
  • This paper presents a new control approach for designing a coordinated controller for static VAR compensator system. A SVC constructed by a Fixed Capacitor and a Thyristor Controlled Reactor is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. A design of linear quadratic controller based on optimal controller depends on choosing weighting matrices. A coordinated optimal controller is achieved by minimizing a quadratic performance index using dynamic programming techniques. The selection of weighting matrices is usually carried out by trial and error which is not a trivial problem. We proposed a efficient method using GA of finding weighting matrices for optimal control law. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

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Characterization of Concentrated Proteins Recovered from Anchovy Engraulis japonicus using Supercritical Carbon Dioxide (초임계 이산화탄소를 이용하여 멸치(Engraulis japonicus)로부터 회수된 고농축 단백질의 특성)

  • Lee, Seung-Mi;Yun, Jun-Ho;Lee, Joo-Hee;Chun, Byung-Soo
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.45 no.3
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    • pp.201-206
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    • 2012
  • Supercritical carbon dioxide ($SCO_2$) extraction was used to recover concentrated proteins and to remove lipids and odor causing compounds from anchovy. Engraulis japonicus $SCO_2$ was used as the solvent for extraction, which was performed in a semi-batch flow reactor. The experimental conditions used were pressure, 15-25 MPa; temperature, $40-60^{\circ}C$ and sample size, 500 ${\mu}m$. The proteins obtained under these conditions performed well in a sensory evaluation; moreover, effective lipids and odor removal was achieved. The stability and characteristics of the proteins recovered with different solvents were also evaluated. The samples were sterilized by processing with $SCO_2$. Escherichia coli was not detected after storage for several days. The sensory characteristics were found to be superior to those of a sample produced by hexane extraction. Thus, the protein concentrate was obtained at $60^{\circ}C$ and 25 MPa was deemed valuable as a foodstuff.

$TiO_2$-Ni inverse Catalyst for CRM Reactions with High Resistance to Coke Formation

  • Seo, Hyun-Ook;Sim, Jong-Ki;Kim, Kwang-Dae;Kim, Young-Dok;Lim, Dong-Chan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.267-267
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    • 2012
  • $TiO_2$-Ni inverse catalysts were prepared using atomic layer deposition (ALD) process and catalytic $CO_2$ reforming of methane (CRM) reaction over catalysts (either bare Ni or $TiO_2$ coated-Ni particles) were performed using a continuous flow reactor at $800^{\circ}C$. $TiO_2$-Ni inverse catalyst showed higher catalytic reactivity at initial stage of CRM reactions at $800^{\circ}C$ comparing to bare Ni catalysts. Moreover, catalytic activity of $TiO_2$/Ni catalyst was kept high during 13 hrs of the CRM reactions at $800^{\circ}C$, whereas deactivation of bare Ni surface was started within 1hr under same conditions. The results of surface analysis using SEM, XPS, and Raman showed that deposition of graphitic carbon was effectively suppressed in a presence of $TiO_2$ nanoparticles on Ni surface, thereby improving catalytic reactivity and stability of $TiO_2$/Ni catalytic systems. We suggest that utilizing decoration effect of metal catalyst with oxide nanoaprticles is of great potential to develop metal-based catalysts with high stability and reactivity.

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Effect of inlet throttling on thermohydraulic instability in a large scale water-based RCCS: An experimental study

  • Qiuping Lv;Matthew Jasica;Darius Lisowski;Zhiee Jhia Ooi;Rui Hu;Mitch Farmer
    • Nuclear Engineering and Technology
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    • v.56 no.2
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    • pp.655-665
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    • 2024
  • The objective of the present experimental study is to investigate the effect of inlet throttling on the thermohydraulic stability of a large scale water-based Reactor Cavity Cooling System (RCCS). The test was performed using the water-based Natural convection Shutdown heat removal Test Facility (NSTF) at Argonne, which represented a ½ axial scale and 12.5° sector slice of the full scale Framatome 625 MWt SC-HTGR RCCS concept. A two-phase steady state was first established through direct condensate refill, followed by increased inlet throttling over 10 stages, corresponding to a loss coefficient K over the range of 0.05-653. With the inlet throttling gradually increased, the system experienced a unique transition process between stabilization and destabilization. Through a stability analysis, three instability mechanisms were identified in the present test, including a compound mechanism due to both natural circulation oscillations (NCOs) and density wave oscillations (DWOs), Type-II DWOs, and geysering.

Development of Optimum Process for Continuous Hydrolysis of Fish Skin Gelatin Using a Three-Step Recycle Membrane Reactor (재순환 3단계 막반응기를 이용한 어피젤라틴의 연속적 가수분해 최적화 공정 개발)

  • Kim, Se-Kwon;Byun, Hee-Guk
    • Applied Chemistry for Engineering
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    • v.5 no.4
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    • pp.681-697
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    • 1994
  • The enzymatic hydrolysate of gelatin extracted from fish skin was fractionated and recycled through the membrane reactor according to the molecular weight for the purpose of using as functional material. In addition, the enzymatic hydrolysis conditions of gelatin, enzyme stability by membrane and mechanical shear, and effect on the long-term operational stability of the recycle membrane reactor were investigated. Using the pH-drop technique, Alcalase, pronase E and collagenase were identified as the most suitable enzymes for the hydrolysis of fish skin gelatin. The optimum hydrolysis conditions in the 1st-step membrane reactor(1st-SMR) by Alcalase were enzyme concentration 0.2mg/ml, substrate-to-enzyme ratio(S/E) 50(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the 2nd-SMR by pronase E were enzyme concentration 0.3mg/ml, S/E 33(w/w), $50^{\circ}C$, pH 8.0, reaction volume 600ml and flow rate 6.14ml/min. In the case of 3rd-SMR, enzyme concentration 0.1mg/ml, S/E 100(w/w), $37^{\circ}C$, pH 7.5, reaction volume 600ml and flow rate 10ml/min. Decreased enzyme activities by mechanical shear and membrane were 30% and 15% in the 1st-SMR, were 14% and 5% in the 2nd-SMR, and 18% and 8% in the 3rd-SMR, respectively. Under the optimum conditions, the degree of hydrolysis in the 1st, 2nd and 3rd-SMR were 3.5%(Kjeldahl method, 87%), 3.1%(77%) and 2.7%(70%), respectively. The productivity of hydrolysate in the continuous three-step membrane reactor was 430mg per enzyme(mg) for 10 times of volume replacements.

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Variation of Optimum Operational pH in Partial Nitritation (암모니아 폐수의 부분아질산화에서 최적 운전 pH의 변동)

  • Bae, Wookeun;Khan, Hammad
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.5
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    • pp.228-235
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    • 2016
  • Nitrite accumulation is essential for constructing an anammox process. As the pH in the reactor exerts a complicated and strong influence on the reaction rate, we investigated its effects upon treatment of an ammonic wastewater (2,000 mgN/L) through modeling and experiment. The modeling results indicated that the reaction stability is strongly affected by pH, which results in a severe reduction of the 'stable region' of operation under alkaline environments. On a coordinate of the total ammonia nitrogen (TAN) concentration vs. pH, the maximal stable reaction rates and the maximal nitrite accumulation potentials could be found on the 'stability ridge' that separates the stable region from the unstable region. We achieved a stable and high ammonia oxidation rate (${\sim}6kgN/m^3-d$) with a nitrite accumulation ratio of ~99% when operated near the 'stability ridge'. The optimum pH that can be observed in experiments varies with the TAN concentrations utilized, although the intrinsic optimum pH is fixed. The direction of change is that the optimum operational pH falls as the TAN concentration increases, which is in excellent accordance with the observations in the literature. The optimum operational pH for 95% nitritation was predicted to be ~8.0, whereas it was ~7.2 for 55% partial nitritation to produce an anammox feed in our experimental conditions.