Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air

Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air PDF Author: Moses A. Muci
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ISBN:
Category :
Languages : en
Pages : 284

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Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air

Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air PDF Author: Moses A. Muci
Publisher:
ISBN:
Category :
Languages : en
Pages : 284

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Thermal-Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air. Part I

Thermal-Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Air. Part I PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 185

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This experimental study investigates the thermal hydraulic behavior and the heat removal performance for a scaled Reactor Cavity Cooling System (RCCS) with air. A quarter-scale RCCS facility was designed and built based on a full-scale General Atomics (GA) RCCS design concept for the Modular High Temperature Gas Reactor (MHTGR). The GA RCCS is a passive cooling system that draws in air to use as the cooling fluid to remove heat radiated from the reactor pressure vessel to the air-cooled riser tubes and discharged the heated air into the atmosphere. Scaling laws were used to preserve key aspects and to maintain similarity. The scaled air RCCS facility at UW-Madison is a quarter-scale reduced length experiment housing six riser ducts that represent a 9.5° sector slice of the full-scale GA air RCCS concept. Radiant heaters were used to simulate the heat radiation from the reactor pressure vessel. The maximum power that can be achieved with the radiant heaters is 40 kW with a peak heat flux of 25 kW per meter squared. The quarter-scale RCCS was run under different heat loading cases and operated successfully. Instabilities were observed in some experiments in which one of the two exhaust ducts experienced a flow reversal for a period of time. The data and analysis presented show that the RCCS has promising potential to be a decay heat removal system during an accident scenario.

Thermal Hydraulic Analysis of University of Wisconsin-Madison's Experimental Air-cooled Reactor Cavity Cooling System Using RELAP5

Thermal Hydraulic Analysis of University of Wisconsin-Madison's Experimental Air-cooled Reactor Cavity Cooling System Using RELAP5 PDF Author: Donghyun Suh
Publisher:
ISBN:
Category :
Languages : en
Pages : 90

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Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Water

Thermal Hydraulic Analysis of an Experimental Reactor Cavity Cooling System with Water PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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This experimental study investigated the thermal hydraulic behavior and boiling mechanisms present in a scaled reactor cavity cooling system (RCCS). The experimental facility reflects a 1/4 scale model of one conceptual design for decay heat removal in advanced GenIV nuclear reactors. Radiant heaters supply up to 25 kW/m2 onto a three parallel riser tube and cooling panel test section assembly, representative of a 5° sector model of the full scale concept. Derived similarity relations have preserved the thermal hydraulic flow patterns and integral system response, ensuring relevant data and similarity among scales. Attention will first be given to the characterization of design features, form and heat losses, nominal behavior, repeatability, and data uncertainty. Then, tests performed in single-phase have evaluated the steady-state behavior. Following, the transition to saturation and subsequent boiling allowed investigations onto four parametric effects at two-phase flow and will be the primary focus area of remaining analysis. Baseline conditions at two-phase flow were defined by 15.19 kW of heated power and 80% coolant inventory, and resulted in semi-periodic system oscillations by the mechanism of hydrostatic head fluctuations. Void generation was the result of adiabatic expansion of the fluid due to a reduction in hydrostatic head pressure, a phenomena similar to flashing. At higher powers of 17.84 and 20.49 kW, this effect was augmented, creating large flow excursions that followed a smooth and sinusoidal shaped path. Stabilization can occur if the steam outflow condition incorporates a nominal restriction, as it will serve to buffer the short time scale excursions of the gas space pressure and dampen oscillations. The influences of an inlet restriction, imposed by an orifice plate, introduced subcooling boiling within the heated core and resulted in chaotic interactions among the parallel risers. The penultimate parametric examined effects of boil-off and inventory loss, where five different stages of natural circulation flow were identified: single-phase heating, transitional nucleate boiling, hydrostatic head fluctuations, stable two-phase flow, and geysering. Finally, the implementation of the model RCCS to a full scale plant was investigated by a multivariate test simulating an hypothetical accident scenario.

Experimental Study of the Thermal-hydraulic Phenomena in the Reactor Cavity Cooling System and Analysis of the Effects of Graphite Dispersion

Experimental Study of the Thermal-hydraulic Phenomena in the Reactor Cavity Cooling System and Analysis of the Effects of Graphite Dispersion PDF Author: Rodolfo Vaghetto
Publisher:
ISBN:
Category :
Languages : en
Pages :

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An experimental activity was performed to observe and study the effects of graphite dispersion and deposition on thermal hydraulic phenomena in a Reactor Cavity Cooling System (RCCS). The small scale RCCS experimental facility (16.5cm x 16.5cm x 30.4cm) used for this activity represents half of the reactor cavity with an electrically heated vessel. Water flowing through five vertical pipes removes the heat produced in the vessel and releases it in the environment by mixing with cold water in a large tank. PIV technique was used to study the velocity field of the air inside the cavity. A set of 52 thermocouples was installed in the facility to monitor the temperature profiles of the vessel and pipes walls and air. 10g of a fine graphite powder (particle size average 2 [mu]m) were injected into the cavity through a spraying nozzle placed at the bottom of the vessel. Temperatures and air velocity field were recorded and compared with the measurements obtained before the graphite dispersion, showing a decrease of the temperature surfaces which was related to an increase in their emissivity. The results contribute to the understanding of the RCCS capability in case of an accident scenario.

Characterization of the Thermal Hydraulic Behavior of an Experimental Reactor Cavity Cooling System with Water

Characterization of the Thermal Hydraulic Behavior of an Experimental Reactor Cavity Cooling System with Water PDF Author: Michael Joseph Gorman
Publisher:
ISBN:
Category :
Languages : en
Pages :

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An existing experimental Reactor Cavity Cooling System using water as the coolant received extensive instrumentation and control upgrades to allow for a thorough investigation into the single-phase flow behavior of the system under a variety of experimental conditions. Base level conditions used a uniform heat flux at a power level appropriately scaled from a benchmark computer simulation of the Gas Turbine Modular Helium Reactor (GT-MHR) using scaling relationships derived by Argonne National Laboratory. Experiments were setup to gauge the effects of flow throttling, non-uniform heat flux profiles, alternate power levels and alternate coolant inventory levels on the flow distribution in the Cooling Panel, and to investigate the relationships between system variables of applied power, the temperature difference across the Cooling Panel ([delta]T) and flowrate. In addition, a single scoping experiment was executed to observe system performance with coolant at the saturation temperature. The system variables proved to have highly linear relationships amongst each other under all experimental conditions. Flow instabilities were observed in the form of counter-phase sinusoidal oscillations of flowrate and [delta]T, the frequency thereof showed a roughly linear relationship with power. Ultrasonic Velocity Profiling (UVP) was used to determine the flow distribution, which increased at the outlet side of the panel with either increased system flowrate or higher heat flux applied to the outlet side, and vice-versa. The effect caused by flowrate changes was the same whether due to a change in power level or throttling, indicating the fluid's momentum is the driving factor. The phenomenon of sudden, high velocity, short duration flow excursions, called geysering, was observed as the system coolant was brought to saturation. This was caused by the trapping of non-condensable gases in the top horizontal section of the flow loop, which in turn brought the flowrate down considerably, increasing residence time and temperature of the coolant in the Cooling Panel. Subsequent rise of saturated coolant to a higher elevation in the hot leg resulted in flashing of the coolant to steam, whose sudden expansion drove the flow excursion. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155387

Scaling Approach and Thermal-hydraulic Analysis in the Reactor Cavity Cooling System of a High Temperature Gas-cooled Reactor and Thermal-jet Mixing in a Sodium Fast Reactor

Scaling Approach and Thermal-hydraulic Analysis in the Reactor Cavity Cooling System of a High Temperature Gas-cooled Reactor and Thermal-jet Mixing in a Sodium Fast Reactor PDF Author: Olumuyiwa A. Omotowa
Publisher:
ISBN:
Category : Fast reactors
Languages : en
Pages : 502

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Experimental and Computational Study of a Scaled Reactor Cavity Cooling System

Experimental and Computational Study of a Scaled Reactor Cavity Cooling System PDF Author: Rodolfo Vaghetto
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The 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. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151742

Reactor Cavity Cooling System Heat Removal Analysis for a High Temperature Gas Cooled Reactor

Reactor Cavity Cooling System Heat Removal Analysis for a High Temperature Gas Cooled Reactor PDF Author: Hong-Chan Wei
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ISBN:
Category :
Languages : en
Pages :

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ABSTRACT: The HTR-10 is a small high temperature gas-cooled reactor. It is an experimental pebble-bed helium cooled reactor with a maximum power of 10 MW, constructed between 2000 and 2003 in China. The study focuses on the thermal-fluid analysis of the Reactor Cavity Cooling System (RCCS) with water flows up the pipes to cool the containment. Computational fluid dynamics (CFD) is used to study local heat transfer phenomena in the HTR-10 containment. Heat is transferred to the RCCS mainly via radiation, and to a lesser extent via natural convection. CFD allows for detailed modeling of both heat transfer modes. Sensitivity analyses on the computational grid and the physics models are performed to optimize the simulation. This leads to the use of the k-[omega] model for turbulence and Discrete Ordinates model for radiation. A 2D axisymmetric model is developed to simulate two scenarios from the HTR-10 benchmark exercises provided in the IAEA Coordinated Research Program (CRP-3). The first is a heat up experiment at a reactor power of 200 kW. The experiment simulates normal operation at low power and aims at verifying the RCCS heat removal capability under steady-state conditions. The second is a transient depressurized loss of heat sink accident. In this situation, the reactor is assumed to be running initially at full power, and then the temperature of the core barrel rises over the next 40 hours, peaks, and falls over the next 72 hours. Three fluids are modeled: the helium inside the pressure vessel and outside the core vessel, air in the containment, and water in the RCCS. The boundary conditions are a temperature profile on the core barrel and adiabatic conditions on the containment walls. The simulations lead to safe values of temperature for all the reactor components; also, the computed temperatures compare well with previous simulations performed for the CRP-3.

Thermal-Hydraulic Analysis of Nuclear Reactors

Thermal-Hydraulic Analysis of Nuclear Reactors PDF Author: Bahman Zohuri
Publisher: Springer
ISBN: 3319174347
Category : Science
Languages : en
Pages : 667

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Book Description
This text covers the fundamentals of thermodynamics required to understand electrical power generation systems and the application of these principles to nuclear reactor power plant systems. It is not a traditional general thermodynamics text, per se, but a practical thermodynamics volume intended to explain the fundamentals and apply them to the challenges facing actual nuclear power plants systems, where thermal hydraulics comes to play. Written in a lucid, straight-forward style while retaining scientific rigor, the content is accessible to upper division undergraduate students and aimed at practicing engineers in nuclear power facilities and engineering scientists and technicians in industry, academic research groups, and national laboratories. The book is also a valuable resource for students and faculty in various engineering programs concerned with nuclear reactors. This book also: Provides extensive coverage of thermal hydraulics with thermodynamics in nuclear reactors, beginning with fundamental definitions of units and dimensions, thermodynamic variables, and the Laws of Thermodynamics progressing to sections on specific applications of the Brayton and Rankine cycles for power generation and projected reactor systems design issues Reinforces fundamentals of fluid dynamics and heat transfer; thermal and hydraulic analysis of nuclear reactors, two-phase flow and boiling, compressible flow, stress analysis, and energy conversion methods Includes detailed appendices that cover metric and English system units and conversions, detailed steam and gas tables, heat transfer properties, and nuclear reactor system descriptions