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On the Role of Microstructure on the Burst Properties of Oxide Dispersion Strengthened FeCrAl Alloys During Simulated Loss-of-Coolant Accident Conditions
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Analysis and modeling of coolants and coolers for specimen transportation
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Developing And Scaling an OpenFOAM Model to Study Turbulent Flow in a HFIR Coolant Channel
Improving the understanding of how computational fluid dynamics (CFD) direct numerical simulations (DNS) of flows in the High Flux Isotope Reactor (HFIR) perform when run in parallel using the high performance computing (HPC) platform Summit at the Oak Ridge Leadership Computing Facility (OLCF) is of particular importance to boost the computational tools used to support HFIR conversion to low enriched fuel (LEU). Evaluation of scaling performance was driven by the increasing importance of graphics processing unit (GPU) usage in HPC, which is becoming the standard for modern supercomputers such as Summit. The desired results are to obtain a strong positive correlation between the computational resources dedicated to a problem and the relative speed-up of the simulation in comparison to a benchmark. This capability will allow substantially improvement in HFIR flow analytical capabilities, specifically when predicting turbulence properties at high Reynolds numbers. The study leverages previous simulation results performed with code PHASTA (finite element) on HPC platforms Cori (NERSC) and Theta (ALCF) [1] with computing options provided in the computing platform OpenFOAM (finite volume) at OLCF. Transitioning from PHASTA to OpenFOAM will (1) eliminate dependence on third-party software for mesh generation and manipulation, (2) reduce resource needs by employing modern architectures, and (3) build expertise for future modeling of HFIR-specific problems like heat transfer in involute geometry, entrance effects, flow structure in channel corners, and so on—all important issues when defining the available thermal margins in the transition to LEU. CPUs and GPUs differ significantly in their architecture and utilization, as discussed in the literature [2]. The most important differences are in the approach to computations and their memory. A single GPU contains a large quantity of cores, enabling it to perform with a much higher throughput than a CPU, but execution requires a different approach. GPU codes execute instructions using the Single-Instruction Multiple-Thread (SIMT) approach in which a single instruction is used for groups of threads called warps. A warp typically consists of 32 threads which must execute the same set of instructions, although on separate threads. Alternately, a CPU has far fewer cores that are much more flexible in their operation, excelling at quickly performing more complex serial computations. This is why GPUs have greater throughput when properly utilized. The second important difference is seen when comparing their memory spaces. Limited memory allocations and CPU–GPU communications cause a significant bottleneck in GPU-accelerated programs. Further study was required to properly take advantage of GPU resources. A comprehensive analysis of code performance and the model-specific features of turbulence constitutes the core of this work. In this study, a DNS simulation of HFIR channel turbulence was performed with the finite volume CFD code OpenFOAM v2112 and CUDA v11.0 on Red Hat Enterprise Linux v8.2. The OpenFOAM installation had AMGx integrated to enable GPU acceleration and utilizes the PETSc4FOAM library. The computational resources and the problem size were scaled on CPU and CPU + GPU architectures to gain a better understanding of the performance of a DNS problem on modern computing hardware. The study aimed to analyze the scaling of the code exclusively on CPUs and then to examine the scaling of the codes with GPU acceleration enabled. Scaling studies included CPU and GPU acceleration on a mesh of varying resolution to analyze the impact of problem size relative to computational resources. In the course of preparing the GPU configuration on Summit, mainly using the AMGX solvers, difficulties were encountered stemming from constant changes resulting from extensive ongoing development activities and the changing environment. This resulted in the inability to complete the GPU portion of the work. The code was compiled and tested, but production runs to assess acceleration were not performed because the used discretional compute time allocation expired as year-end approached. The Summit HPC platform is scheduled for decommissioning in 2024, making it unattractive for future use with Nvidia-based GPUs. Therefore, the work will be moved onto NERSC machines in FY24. An application was prepared and submitted, and sufficient node-hours were awarded to continue the research in the next calendar year. This report summarizes work performed thus far, which mostly focused on CPU OpenFOAM computing.
In-Pile Loss of Coolant Accident Testing at TREAT
Several hot-cell based LOCA test apparatuses still exist in various institutions across the world. These facilities typically surround rods with infrared electrical heaters to simulate LOCA conditions on the cladding. Despite its utility for cladding-focused testing, the furnace-based external heating method creates an inverted temperature gradient in fuel pellets compared to a true LOCA where radioisotope decay heat generates internal heat. Capturing the correct temperature gradient is essential in simulating the thermomechanical stress in fuel pellets, and hence a crucial design parameter investigating FFRD during a postulated LOCA. This thermomechanical stress state, for which the evolution of fuel pellet centerline and cladding temperatures is a good figure of merit, was the primary parameter investigated during conception of the LOCA-SERTTA device.
Gas Coolant Channel Optimization for Transformational Challenge Reactor
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Dual Coolant Liquid Metal Divertor Development
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External Temperature Effects on Thermal Features of Reactor Coolants System and Power Level Estimation
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Data center coolant switch
A data center cooling system has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during a first mode. When an appropriate time has been reached to switch from the first mode to a second mode, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid (compared to the first fluid). It has a second heat transfer fluid freezing point, lower than the first heat transfer fluid freezing point, and sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.
Operation of Broad Area High Power Diode Lasers Immersed in Coolant
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Coolant Design and Analysis for Low Thermal Conductivity Components of Linear Plasma Devices
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Coolant delivery via an independent cooling circuit
An embodiment of an independent cooling circuit for selectively delivering cooling fluid to a component of a gas turbine system includes: a plurality of independent circuits of cooling channels embedded within an exterior wall of the component, wherein the plurality of circuits of cooling channels are interwoven together; an impingement plate; and a plurality of feed tubes connecting the impingement plate to the exterior wall of the component and fluidly coupling each of the plurality of circuits of cooling channels to at least one supply of cooling fluid, wherein, in each of the plurality of circuits of cooling channels, the cooling fluid flows through the plurality of feed tubes into the circuit of cooling channels only in response to a formation of a breach in the exterior wall of the component that exposes at least one of the cooling channels of the circuit of cooling channels.
Data center coolant switch
A data center cooling system has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during a first mode. When an appropriate time has been reached to switch from the first mode to a second mode, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid (compared to the first fluid). It has a second heat transfer fluid freezing point, lower than the first heat transfer fluid freezing point, and sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.
Primary Coolant Apparatus Test (PCAT): an experimental facility for MARVEL microreactor
Description of the PCAT facility and RELAP5-3D model of it.
RELAP5-3D Validation Using the Primary Coolant Apparatus Test (PCAT) Facility
Presentation for discussing the use for PCAT for validating RELAP5-3D
Wick assisted embedded evaporative cooling of motors
A cooling system for an electric motor that includes a stator having a plurality of slot windings and a rotor, coaxial with the stator, having a plurality of magnets, includes a coolant inlet to the motor and a coolant outlet from the motor. A coolant pathway is in fluid communication with the inlet and the outlet. Heat is transferable from the slot windings to the coolant pathway. A coolant flows through the coolant pathway and is in a liquid phase as it enters the coolant inlet, changing into a gaseous phase as heat is transferred to the coolant from the slot windings. A cooling loop is in fluid communication with the coolant inlet and the coolant outlet. The cooling loop cools the coolant so that substantially all of the coolant is in the liquid phase when it enters the coolant inlet.
Integral LOCA fragmentation test on high-burnup fuel
Increasing the fuel burnup limit in light water reactors is sought to enhance fuel cycle economics and requires establishing a technical basis. Experimental observations of severe fuel fragmentation under loss-of-coolant-accident conditions at Halden and Studsvik had raised the need for additional considerations during the development of this technical basis. These test data suggested that the burnup threshold for high burnup fuel fragmentation may be influenced by pre-transient power. Additional loss-of-coolant-accident test data is therefore valuable to complement these tests and enhance the current state of understating. Oak Ridge National Lab has developed the Severe Accident Test Station capable of examining the oxidation kinetics and accident response of irradiated fuel and cladding materials for design basis accident and beyond design basis accident scenarios. Severe Accident Test Station provides various temperature profiles, steam, and the thermal shock conditions necessary for integral loss of coolant accident testing, defueled oxidation quench testing, and high-temperature beyond design basis accident testing. Severe Accident Test Station has been successfully installed and demonstrated in the Irradiated Fuels Examination Laboratory at Oak Ridge National Lab. Furthermore, descriptions of the in-cell re-fabrication capabilities and assembly of the loss-of-coolant-accident test train are provided. Installation of the Severe Accident Test Station system and in-cell re-fabrication restores United States capability to examine postulated and extended loss-of-coolant-accident conditions on spent fuel and cladding and provides a platform for evaluating advanced fuel and accident-tolerant fuel cladding concepts. Lastly, three in-cell integral loss-of-coolant-accident test were performed in the Severe Accident Test Station and compared to the Nuclear Regulatory Commission sponsored loss-of-coolant-accident test as well as the original loss-of-coolant-accident test performed at Argonne National Lab. Finally, the results of these tests as well as all publicly available integral loss-of-coolant-accident test were used to validate a threshold for high burnup fuel fragmentation.
Provisioning cooling elements for chillerless data centers
Systems and methods for cooling include one or more computing structures, a heat rejection system configured to cool coolant, and one or more heat exchangers configured to selectively transfer heat from coolant in the intra-structure cooling system to coolant in the heat rejection system. Each computing structure includes one or more cooled servers and an intra-structure cooling system configured to selectively provide coolant to the one or more cooled servers. A controller is configured to adjust cooling of the coolant in accordance with ambient temperature information, to decrease cooling of the coolant if the coolant temperature falls below a first coolant threshold temperature by disengaging one or more heat exchangers, and to turn on additional servers if the coolant temperature is below the first cool and threshold and all heat exchangers have been disengaged.