Computational fluid dynamics simulation of corium spreading
File(s)
Author(s)
Perrier, Hugo
Type
Thesis
Abstract
In the event of a severe accident in a nuclear reactor involving reactor core degradation, molten
core materials called Corium can form. The interaction of Corium with the concrete of reactor
containment buildings may threaten the integrity of nuclear power plants. A technical solution
to prevent the penetration of Corium into the concrete base-mat is the implementation of
a core-catcher designed to collect the Corium and spread it over a large area to be cooled
efficiently.
Due to the complexity of Corium spreading simulations, standard numerical methods used in
Computational Fluid Dynamics (CFD) may not be applicable to Corium flows. Therefore, the
work presented in this thesis investigates in detail the errors associated with the numerical
simulation of Corium flows.
In particular, the numerical representation of the interface between two immiscible fluids, such
as Corium and air, is challenging. This thesis identifies numerical diffusion of temperature,
which is a numerical error associated with the spatial discretisation process, in the vicinity of
the Corium/air interface, as a source of error for Corium spreading simulations. A numerical
strategy is proposed and evaluated on several test cases with known solutions. It is shown
that, compared to standard numerical methods, the proposed strategy significantly reduces
numerical diffusion.
The numerical methods studied in this thesis are validated against experimental results from
the VULCANO VE-U7 Corium spreading experiment. The simulation results obtained are
compared to experimental results as well as other simulation results available in the scientific
literature. It is shown that the choice of numerical methods affects the spreading predictions,
however, the uncertainty of Corium properties is the major source of uncertainty in the simulation results
core materials called Corium can form. The interaction of Corium with the concrete of reactor
containment buildings may threaten the integrity of nuclear power plants. A technical solution
to prevent the penetration of Corium into the concrete base-mat is the implementation of
a core-catcher designed to collect the Corium and spread it over a large area to be cooled
efficiently.
Due to the complexity of Corium spreading simulations, standard numerical methods used in
Computational Fluid Dynamics (CFD) may not be applicable to Corium flows. Therefore, the
work presented in this thesis investigates in detail the errors associated with the numerical
simulation of Corium flows.
In particular, the numerical representation of the interface between two immiscible fluids, such
as Corium and air, is challenging. This thesis identifies numerical diffusion of temperature,
which is a numerical error associated with the spatial discretisation process, in the vicinity of
the Corium/air interface, as a source of error for Corium spreading simulations. A numerical
strategy is proposed and evaluated on several test cases with known solutions. It is shown
that, compared to standard numerical methods, the proposed strategy significantly reduces
numerical diffusion.
The numerical methods studied in this thesis are validated against experimental results from
the VULCANO VE-U7 Corium spreading experiment. The simulation results obtained are
compared to experimental results as well as other simulation results available in the scientific
literature. It is shown that the choice of numerical methods affects the spreading predictions,
however, the uncertainty of Corium properties is the major source of uncertainty in the simulation results
Version
Open Access
Date Issued
2018-07
Date Awarded
2019-06
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Denner, Fabian
Eaton, Matthew
van Wachem, Berend
Sponsor
Rolls-Royce Group plc
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)