Browsing by Subject "RCCS"
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Item Analysis of the Reactor Cavity Cooling System for Very High Temperature Gas-cooled Reactors Using Computational Fluid Dynamics Tools(2011-08-08) Frisani, AngeloThe design of passive heat removal systems is one of the main concerns for the modular Very High Temperature Gas-Cooled Reactors (VHTR) vessel cavity. The Reactor Cavity Cooling System (RCCS) is an important heat removal system in case of accidents. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The commercial Computational Fluid Dynamics (CFD) STAR-CCM+/ V3.06.006 code was used for three-dimensional system modeling and analysis of the RCCS. Two models were developed to analyze heat exchange in the RCCS. Both models incorporate a 180 degree section resembling the VHTR RCCS bench table test facility performed at Texas A&M University. All the key features of the experimental facility were taken into account during the numerical simulations. Two cooling fluids (i.e., water and air) were considered to test the capability of maintaining the RCCS concrete walls temperature below design limits. Mesh convergence was achieved with an intensive parametric study of the two different cooling configurations and selected boundary conditions. To test the effect of turbulence modeling on the RCCS heat exchange, predictions using several different turbulence models and near-wall treatments were evaluated and compared. The models considered included the first-moment closure one equation Spalart-Allmaras model, the first-moment closure two-equation k-e and k-w models and the second-moment closure Reynolds Stress Transport (RST) model. For the near wall treatments, the low y+ and the all y+ wall treatments were considered. The two-layer model was also used to investigate the effect of near-wall treatment. The comparison of the experimental data with the simulations showed a satisfactory agreement for the temperature distribution inside the RCCS cavity medium and at the standpipes walls. The tested turbulence models demonstrated that the Realizable k-e model with two-layer all y+ wall treatment performs better than the other k-e models for such a complicated geometry and flow conditions. Results are in satisfactory agreement with the RST simulations and experimental data available. A scaling analysis was developed to address the distortion introduced by the experimental facility and CFD model in simulating the physics inside the RCCS system with respect to the real plant configuration. The scaling analysis demonstrated that both the experimental facility and CFD model give a satisfactory reproduction of the main flow characteristics inside the RCCS cavity region, with convection and radiation heat exchange phenomena being properly scaled from the real plant to the model analyzed.Item Effects of three-dimensional culture conditions on skeletal muscle myoblasts(2007-03-30) Michele Lynn Marquette; Marguerite Sognier; Robert Leonard; Mary Moslen; Jeff Rabek; Brian HashemiEffects of Three-dimensional Culture Conditions on Skeletal Muscle Myoblasts\r\n\r\nPublication No._____________\r\n\r\n\r\nMichele Lynn Marquette, Ph.D.\r\nThe University of Texas Medical Branch, 2007\r\n\r\nSupervisor: Marguerite A. Sognier\r\n\r\nThe objectives of this research were to: 1) develop a three-dimensional in vitro model; and 2) subsequently, utilize this model to investigate mechanisms of myoblast adhesion, fusion, and differentiation. C2C12 cells were examined as pre-aggregated single cells and multicellular aggregates in the Rotary Cell Culture System (RCCS). At the time intervals tested, RCCS cultured cells maintained viability and did not exhibit increased apoptosis markers such as Caspase 3 (activated) and phosphatydylserine. In contrast, increases in cell death and apoptotic markers were noted in suspension culture (SC) control cells. RCCS cultured cells fused to form multinucleated syncitia and expressed sarcomeric myosin heavy chain (MHC) in significantly higher levels than SC aggregates after cultivation for 3 and 6 days. This occurred in the presence of mitogens without exogenous matrix or support structures. Myoblast fusion was inhibited by exposure to soluble anti-Neural-cadherin antibody, but this treatment increased MHC levels assessed using immunohistochemistry.\r\nDuring early RCCS culture, myoblasts exhibited numerous cytoplasmic protrusions (podia). Microscopic examination of cells cultured in RCCS and SC revealed significantly more and slightly longer podia in the RCCS at 3, 6, and 9-hours. Podia were F-actin dependent as shown by exposure to an F-actin depolymerizing agent, Latrunculin A. Podia were inhibited, but recovered upon Latrunculin A removal. \r\nPodia were postulated to play a role in cell-cell adhesion in conjunction with Neural Cadherin (N-cadherin), an adhesion molecule important in myoblast differentiation. To determine if N-cadherin was critical to cell-cell adhesion, RCCS cultured cells were examined for the presence of N-cadherin at both the podia and membrane using confocal microscopy. N-cadherin levels decreased at the podia and membrane of RCCS cultured cells but not in SC cells at 3, 6, and 9-hours. \r\nIn summary, these results revealed: 1) podia formation is F-actin dependent but N-cadherin independent; 2) N-cadherin is critical for myoblast maturation; 3) synctia formation and differentiation can occur with mitogens present, without exogenous substrates in the RCCS; 4) this novel myoblast model test system is suitable for defining muscle development/regeneration processes, identification of molecular targets for development of therapies, and potential regenerative medicine applications.\r\n \r\nItem Experimental and Computational Study of a Scaled Reactor Cavity Cooling System(2013-11-25) Vaghetto, RodolfoThe Very High Temperature Gas-Cooled Reactor (VHTR) is one of the next generation nuclear reactors designed to achieve high temperatures to support industrial applications and power generation. The Reactor Cavity Cooling System (RCCS) is a passive safety system that will be incorporated in the VTHR, designed to remove the heat from the reactor cavity and maintain the temperature of structures and concrete walls under desired limits during normal operation and accident scenarios. A small scale (1:23) water-cooled experimental facility was scaled, designed, and constructed in order to study the complex thermohydraulic phenomena taking place in the RCCS during steady-state and transient conditions. The facility represents a portion of the reactor vessel with nine stainless steel coolant risers and utilizes water as coolant. The facility was equipped with instrumentation to measure temperatures and flow rates and a general verification was completed during the shakedown. A model of the experimental facility was prepared using RELAP5-3D and simulations were performed to validate the scaling procedure. The overall behavior of the facility met the expectations. The steady-state condition was achieved and the facility capabilities were confirmed to be very promising in performing additional experimental tests, including flow visualization, and produce data for code validation. The experimental data produced during the steady-state run were successfully compared with the simulation results obtained using RELAP5-3D, confirming the capabilities of the system code of simulating the thermal-hydraulic phenomena occurring in the reactor cavity.Item Heat Transfer Simulation of Reactor Cavity Cooling System Experimental Facility using RELAP5-3D and Generation of View Factors using MCNP(2013-08-08) Wu, HualiAs one of the most attractive reactor types, The High Temperature Gas-cooled Reactor (HTGR) is designed to be passively safe with the incorporation of Reactor Cavity Cooling System (RCCS). In this paper, a RELAP5-3D simulation model is set up based on the 1/16 scale experimental facility established by Texas A&M University. Also, RELAP5-3D input decks are modified to replicate the experiment procedures and the experimental results are compared with the simulation results. The results show there is a perfect match between experimental and simulation results. Radiation heat transfer dominates in the heat transfer process of high temperature gas-cooled reactor due to its high operation temperature. According to experimental research done with the RCCS facility in Texas A&M University, radiation heat transfer takes up 80% of the total heat transferred to standing pipes. In radiation heat transfer, the important parameters are view factors between surfaces. However, because of the geometrical complexity in the experimental facility, it is hard to use the numerical method or analytical view factor formula to calculate view factors. In this project, MCNP based on the Monte Carlo method is used to generate view factors for RELAP5-3D input. MCNP is powerful in setting up complicated geometry, source definition and tally application. In the end, RCCS geometry is set up using MCNP and view factors are calculated.