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Title: Mixing Processes in High-Level Waste Tanks

Abstract

Mixing and transport in large waste-tank volumes is controlled by the multidimensional equations describing mass, momentum and energy conservation, and by boundary conditions imposed at walls, structures, and fluid inlets and outlets. For large enclosures, careful scaling arguments show that mixing is generated by free buoyant jets arising from the injection of fluid or buoyancy into the enclosure, and by temperature and/or concentration gradients generated near surfaces by heat and mass transfer at walls, cooling tubes, and liquid-vapor interfaces. For large enclosures like waste-tank air spaces, scaling shows that these free and wall jets are generally turbulent and are generally relatively thin. When one attempts to numerically solve the multi-dimensional mass, momentum, and energy equations with CFD codes, very fine grid resolution is required to resolve these thin jet structures, yet such fine grid resolution is difficult or impossible to provide due to computational expense. However, we have shown that the ambient fluid between jets tends to organize into either a homogeneously mixed condition or a vertically stratified condition that can be described by a one-dimensional temperature and concentration distribution. Furthermore, we can predict the transition between the well-mixed and stratified conditions. This allows us to describe mixing processes inmore » large, complex enclosures using one-dimensional differential equations, with transport in free and wall jets modeled using standard integral techniques. With this goal in mind, we are constructing a simple, computationally efficient numerical tool which can be used predicting the transient evolution of fuel and oxygen concentrations in DOE high-level waste tanks following loss of ventilation, and validate the model against a series of experiments.« less

Authors:
Publication Date:
Research Org.:
Department of Nuclear Engineering University of California, Berkeley, Berkeley, CA (US)
Sponsoring Org.:
USDOE Office of Environmental Management (EM) (US)
OSTI Identifier:
826069
Report Number(s):
EMSP-54656-1999
R&D Project: EMSP 54656; TRN: US200424%%423
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 1999
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; BOUNDARY CONDITIONS; DIFFERENTIAL EQUATIONS; DISTRIBUTION; ENERGY CONSERVATION; MASS TRANSFER; OXYGEN; RESOLUTION; TANKS; TRANSIENTS; TRANSPORT; VENTILATION; WASTES

Citation Formats

Peterson, Per F. Mixing Processes in High-Level Waste Tanks. United States: N. p., 1999. Web. doi:10.2172/826069.
Peterson, Per F. Mixing Processes in High-Level Waste Tanks. United States. https://doi.org/10.2172/826069
Peterson, Per F. 1999. "Mixing Processes in High-Level Waste Tanks". United States. https://doi.org/10.2172/826069. https://www.osti.gov/servlets/purl/826069.
@article{osti_826069,
title = {Mixing Processes in High-Level Waste Tanks},
author = {Peterson, Per F},
abstractNote = {Mixing and transport in large waste-tank volumes is controlled by the multidimensional equations describing mass, momentum and energy conservation, and by boundary conditions imposed at walls, structures, and fluid inlets and outlets. For large enclosures, careful scaling arguments show that mixing is generated by free buoyant jets arising from the injection of fluid or buoyancy into the enclosure, and by temperature and/or concentration gradients generated near surfaces by heat and mass transfer at walls, cooling tubes, and liquid-vapor interfaces. For large enclosures like waste-tank air spaces, scaling shows that these free and wall jets are generally turbulent and are generally relatively thin. When one attempts to numerically solve the multi-dimensional mass, momentum, and energy equations with CFD codes, very fine grid resolution is required to resolve these thin jet structures, yet such fine grid resolution is difficult or impossible to provide due to computational expense. However, we have shown that the ambient fluid between jets tends to organize into either a homogeneously mixed condition or a vertically stratified condition that can be described by a one-dimensional temperature and concentration distribution. Furthermore, we can predict the transition between the well-mixed and stratified conditions. This allows us to describe mixing processes in large, complex enclosures using one-dimensional differential equations, with transport in free and wall jets modeled using standard integral techniques. With this goal in mind, we are constructing a simple, computationally efficient numerical tool which can be used predicting the transient evolution of fuel and oxygen concentrations in DOE high-level waste tanks following loss of ventilation, and validate the model against a series of experiments.},
doi = {10.2172/826069},
url = {https://www.osti.gov/biblio/826069}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jun 01 00:00:00 EDT 1999},
month = {Tue Jun 01 00:00:00 EDT 1999}
}