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Title: Multiphysics modeling of two-phase film boiling within porous corrosion deposits

Abstract

Porous corrosion deposits on nuclear fuel cladding, known as CRUD, can cause multiple operational problems in light water reactors (LWRs). CRUD can cause accelerated corrosion of the fuel cladding, increase radiation fields and hence greater exposure risk to plant workers once activated, and induce a downward axial power shift causing an imbalance in core power distribution. In order to facilitate a better understanding of CRUD's effects, such as localized high cladding surface temperatures related to accelerated corrosion rates, we describe an improved, fully-coupled, multiphysics model to simulate heat transfer, chemical reactions and transport, and two-phase fluid flow within these deposits. Our new model features a reformed assumption of 2D, two-phase film boiling within the CRUD, correcting earlier models' assumptions of single-phase coolant flow with wick boiling under high heat fluxes. This model helps to better explain observed experimental values of the effective CRUD thermal conductivity. Finally, we propose a more complete set of boiling regimes, or a more detailed mechanism, to explain recent CRUD deposition experiments by suggesting the new concept of double dryout specifically in thick porous media with boiling chimneys. - Highlights: • A two-phase model of CRUD's effects on fuel cladding is developed and improved. • Thismore » model eliminates the formerly erroneous assumption of wick boiling. • Higher fuel cladding temperatures are predicted when accounting for two-phase flow. • Double-peaks in thermal conductivity vs. heat flux in experiments are explained. • A “double dryout” mechanism in CRUD is proposed based on the model and experiments.« less

Authors:
;
Publication Date:
OSTI Identifier:
22572327
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Computational Physics; Journal Volume: 316; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; CLADDING; CORROSION; FILM BOILING; FINITE ELEMENT METHOD; HEAT FLUX; HEAT TRANSFER; NUCLEAR FUELS; POROUS MATERIALS; POWER DISTRIBUTION; PWR TYPE REACTORS; THERMAL CONDUCTIVITY; TWO-PHASE FLOW

Citation Formats

Jin, Miaomiao, E-mail: mmjin@mit.edu, and Short, Michael, E-mail: hereiam@mit.edu. Multiphysics modeling of two-phase film boiling within porous corrosion deposits. United States: N. p., 2016. Web. doi:10.1016/J.JCP.2016.03.013.
Jin, Miaomiao, E-mail: mmjin@mit.edu, & Short, Michael, E-mail: hereiam@mit.edu. Multiphysics modeling of two-phase film boiling within porous corrosion deposits. United States. doi:10.1016/J.JCP.2016.03.013.
Jin, Miaomiao, E-mail: mmjin@mit.edu, and Short, Michael, E-mail: hereiam@mit.edu. Fri . "Multiphysics modeling of two-phase film boiling within porous corrosion deposits". United States. doi:10.1016/J.JCP.2016.03.013.
@article{osti_22572327,
title = {Multiphysics modeling of two-phase film boiling within porous corrosion deposits},
author = {Jin, Miaomiao, E-mail: mmjin@mit.edu and Short, Michael, E-mail: hereiam@mit.edu},
abstractNote = {Porous corrosion deposits on nuclear fuel cladding, known as CRUD, can cause multiple operational problems in light water reactors (LWRs). CRUD can cause accelerated corrosion of the fuel cladding, increase radiation fields and hence greater exposure risk to plant workers once activated, and induce a downward axial power shift causing an imbalance in core power distribution. In order to facilitate a better understanding of CRUD's effects, such as localized high cladding surface temperatures related to accelerated corrosion rates, we describe an improved, fully-coupled, multiphysics model to simulate heat transfer, chemical reactions and transport, and two-phase fluid flow within these deposits. Our new model features a reformed assumption of 2D, two-phase film boiling within the CRUD, correcting earlier models' assumptions of single-phase coolant flow with wick boiling under high heat fluxes. This model helps to better explain observed experimental values of the effective CRUD thermal conductivity. Finally, we propose a more complete set of boiling regimes, or a more detailed mechanism, to explain recent CRUD deposition experiments by suggesting the new concept of double dryout specifically in thick porous media with boiling chimneys. - Highlights: • A two-phase model of CRUD's effects on fuel cladding is developed and improved. • This model eliminates the formerly erroneous assumption of wick boiling. • Higher fuel cladding temperatures are predicted when accounting for two-phase flow. • Double-peaks in thermal conductivity vs. heat flux in experiments are explained. • A “double dryout” mechanism in CRUD is proposed based on the model and experiments.},
doi = {10.1016/J.JCP.2016.03.013},
journal = {Journal of Computational Physics},
number = ,
volume = 316,
place = {United States},
year = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}