Numerical Investigation of the Spreading and Heat Transfer Characteristics of Ex-Vessel Core Melt

Ye, Insoo; Kim, Jeongeun Alice; Ryu, Changkook; Ha, Kwang Soon; Kim, Hwan Yeol; Song, J. H.

doi:10.5516/net.03.2012.011

Cited by 20 publications

(6 citation statements)

References 7 publications

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“…More recently, strides have been made in the use of commercial CFD codes to analyze core debris spreading behavior. [26] Effects accounted for in this approach include radiation heat transfer, decay heat, and temperaturedependent viscosity. However, crusting behavior and the potential for concrete decomposition and ablation are not modeled.…”

Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

“…Like the other methods described above, this approach is computationally intensive and so the ability to apply this method to longer term transients at reactor scale is limited. [26] Following closure of the Mark I issue, MELTSPREAD development ceased in the early 1990's, at which time the melt spreading database upon which the code had been originally validated was rather limited. In particular, the database used for initial validation consisted of: i) comparison to an analytical solution for the dam break problem, [27] iii) water spreading tests in a 1/10 linear scale model of the Mark I containment by Theofanous et al, [5] and iii) steel spreading tests by Suzuki et al [28] that were also conducted in a Mark I type geometry.…”

Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

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The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior

Farmer

2018

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MELTSPREAD3 is a transient 1-D computer code that has been developed to predict the gravity-driven flow and freezing behavior of molten reactor core materials (corium) in containment geometries. Predictions can be made for corium flowing across surfaces under either dry or wet cavity conditions. The spreading surfaces that can be selected are steel, concrete, a user-specified material (e.g., a ceramic), or an arbitrary combination thereof. The corium can have a wide range of compositions of reactor core materials that includes distinct oxide phases (predominantly 𝑈𝑂 , 𝑍𝑟𝑂 , and steel oxides) plus metallic phases (predominantly Zr and steel). The code requires input that describes the containment geometry, melt "pour" conditions, and cavity atmospheric conditions (i.e., pressure, temperature, and cavity flooding information). For cases in which the cavity contains a preexisting water layer at the time of RPV failure, melt jet breakup and particle bed formation can be calculated mechanistically given the time-dependent melt pour conditions (input data) as well as the heatup and boiloff of water in the melt impingement zone (calculated).For core debris impacting either the containment floor or previously spread material, the code calculates the transient hydrodynamics and heat transfer which determine the spreading and freezing behavior of the melt. The code predicts conditions at the end of the spreading stage, including melt relocation distance, depth and material composition profiles, substrate ablation profile, and wall heatup. Code output can be used as input to other models such as CORQUENCH to evaluate long term core-concrete interaction behavior following the transient spreading stage.MELTSPREAD3 was originally developed to investigate BWR Mark I liner vulnerability, but has been substantially upgraded and applied to other reactor designs (e.g., the EPR), and more recently to the plant accidents at Fukushima Daiichi. The most recent improvements that are documented in this report have been specifically implemented to support industry in developing Severe Accident Water Addition/Severe Accident Water Management (SAWA/SAWM) strategies for Boiling Water Reactors. This document is a Code Manual which contains i) a technology review, ii) descriptions of models and correlations, iii) descriptions of the implicit, finite difference numerical solution scheme, iv) a user's guide, and v) a summary of code validation calculations that have been performed with this version of the code.

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Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior

Farmer

2018

View full text Add to dashboard Cite

show abstract

“…More recently, strides have been made in the use of commercial CFD codes to analyze core debris spreading behavior. [26] Effects accounted for in this approach include radiation heat transfer, decay heat, temperature-dependent viscosity. However, crusting behavior and the potential for concrete decomposition and ablation are not modeled.…”

Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

“…Like the other methods described above, this approach is computationally intensive and so the ability to apply this method to longer term transients is limited. [26] Following closure of the Mark I issue, MELTSPREAD development ceased in the early 1990's, at which time the melt spreading database upon which the code had been originally validated was rather limited. In particular, the database used for initial validation consisted of: i) comparison to an analytical solution for the dam break problem, [27] iii) water spreading tests in a 1/10 linear scale model of the Mark I containment by Theofanous et al, [6] and iii) steel spreading tests by Suzuki et al [28] that were also conducted in a Mark I type geometry.…”

Section: Phenomenology and Literature Reviewmentioning

confidence: 99%

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior, Code Manual – Version3-beta

Farmer

2017

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MELTSPREAD3 is a transient one-dimensional computer code that has been developed to predict the gravity-driven flow and freezing behavior of molten reactor core materials (corium) in containment geometries. Predictions can be made for corium flowing across surfaces under either dry or wet cavity conditions. The spreading surfaces that can be selected are steel, concrete, a user-specified material (e.g., a ceramic), or an arbitrary combination thereof. The corium can have a wide range of compositions of reactor core materials that includes distinct oxide phases (predominantly 2 , 2 , and steel oxides) plus metallic phases (predominantly Zr and steel). The code requires input that describes the containment geometry, melt "pour" conditions, and cavity atmospheric conditions (i.e., pressure, temperature, and cavity flooding information). For cases in which the cavity contains a preexisting water layer at the time of RPV failure, melt jet breakup and particle bed formation can be calculated mechanistically given the time-dependent melt pour conditions (input data) as well as the heatup and boiloff of water in the melt impingement zone (calculated). For core debris impacting either the containment floor or previously spread material, the code calculates the transient hydrodynamics and heat transfer which determine the spreading and freezing behavior of the melt. The code predicts conditions at the end of the spreading stage, including melt relocation distance, depth and material composition profiles, substrate ablation profile, and wall heatup. Code output can be used as input to other models such as CORQUENCH that evaluate long term core-concrete interaction behavior following the transient spreading stage.MELTSPREAD3 was originally developed to investigate BWR Mark I liner vulnerability, but has been substantially upgraded and applied to other reactor designs (e.g., the EPR), and more recently to the plant accidents at Fukushima Daiichi. The most recent round of improvements that are documented in this report have been specifically implemented to support industry in developing Severe Accident Water Management (SAWM) strategies for Boiling Water Reactors. This document is a Code Manual which contains i) a technology review, ii) descriptions of models and correlations, iii) descriptions of the implicit, finite difference numerical solution scheme, iv) a user's guide, and v) a summary of code validation calculations that have been performed to date.

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“…Wittmaack, [28] used the experimental data to compare and verify this code and then used it to model the spreading and flow of molten corium. Ye et al, [23] used a commercial code (FLUENT) to model molten corium spreading utilizing the Volume-of-Fluid (VOF) technique for the different phases. They specified the thermaldependent properties of the molten corium using user-defined functions in the solver.…”

Section: Introductionmentioning

confidence: 99%

A Thermal Approach for Modelling the Concrete Ablation during Molten Corium-Concrete Interaction

Khurshid,

Hassan,

Faizan

et al. 2024

Preprint

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An accident in a nuclear power plant involving a reactor core meltdown would result in instigation of molten corium, which is a mixture of nuclear fuel, claddings and structural components. In this paper, an enthalpy porosity model is proposed to comprehensively analyze the ablation of concrete during the Molten Corium and Concrete Interaction (MCCI) process. The developed numerical model is an extension of the enthalpy-porosity model and is termed as Corium-Concrete Enthalpy Porosity Model (CCEPM). The developed CCEPM Computational Fluid Dynamic (CFD) model can predict natural convection, melting and solidification. The developed model simplifies the complex phenomena of concrete ablation and its melting by incorporating the multi-region approach. The model was implemented in OpenFOAM, by developing a new solver which couples the buoyant-driven natural convection and conjugate heat transfer solvers. The thermal modelling and heat transfer capabilities of the developed solver were verified against experimental data sets. Additionally, the effect of various boundary conditions, concrete thermal conductivity and intensity of decay heat were analyzed to study their impact on concrete ablation. We observed significant low concrete ablation, controlled temperature and velocity field, for the water-cooled boundary condition. Accordingly, the ablation of concrete decreased by 17% just by imposing the water-cooled boundary condition. Similarly, when the thermal conductivity was decreased to 0.43 and 0.13 W/m. K, the ablation of concrete reduced by 38% and 75%, respectively. Furthermore, early cooling of molten corium to decrease decay heat was found to be an effective strategy to mitigate the concrete ablation successfully by 20%.

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Numerical Investigation of the Spreading and Heat Transfer Characteristics of Ex-Vessel Core Melt

Cited by 20 publications

References 7 publications

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior, Code Manual – Version3-beta

A Thermal Approach for Modelling the Concrete Ablation during Molten Corium-Concrete Interaction

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