Numerical simulation of steady-state mixed convection sodium flow experiments
Introduction
Among the nuclear reactor concepts currently being studied around the world are the sodium-cooled fast reactors SFR (Bertrand et al., 2019, Chai et al., 2020, Yeom et al., 2020, Yu et al., 2020, Khan et al., 2020). The main feature of this technology lies in its capacity to consume depleted uranium issued from the pressurized water reactor nuclear fuel cycle.
The thermal–hydraulic flow in this type of reactor could have the particularity of being stratified (Ieda et al., 1990). That is to say that the sodium of the highest temperature could accumulate in the upper part of certain core structures and modify heat exchanges, notably in the event of a primary circuit shutdown or a significant reduction in flow (Tenchine, 2010). The modification of heat exchanges could be accompanied by significant thermal gradients on the metal structures, which would be harmful to maintain the integrity of the mechanical properties of these elements.
For safety reasons, it is therefore necessary to avoid the appearance of thermal stratification of sodium and the robustness of the concepts studied with respect to this point is tested using numerical simulation tools. In order to be able to validate these numerical simulation tools and the mathematical models describing the thermal–hydraulic flow of sodium, a good numerical simulation of experimental results is a key point (Tenchine, 2010).
In this paper, we will present numerical simulation using the TrioCFD Code developed at CEA (Calvin et al., 2002) of experimental results of sodium flow with thermal stratification. The experimental results were obtained in the years 1980 at the CEA thanks to the experimental device SUPERCAVNA (Super Cavity Na) involving several cubic meters of sodium at (Vidil et al., 1988).
Section snippets
The experimental setup
The SUPERCAVNA test section was used at the CEA in Grenoble in the early 1980 s. Its purpose was to study sodium temperature rises due to thermo-gravity stratification of the flow in areas of the reactor that may have low flow velocities (such as parts of the lower plenum) following an emergency shutdown (Vidil et al., 1988) or a significant reduction in the secondary coolant flow system (Tenchine, 2010). It is schematically composed (Cf. Fig. 1) of the assembly of two parts. The first part
Numerical simulation using TrioCFD
TrioCFD (formerly Trio_U) is a Computational Fluid Dynamic (CFD) code developed at CEA for many years (Calvin et al., 2002, Tenchine et al., 2012, Angeli et al., 2017) and used to perform numerical simulations in many thermo–hydraulic applications in the nuclear field (Angeli, 2019, Bieder et al., 2019).
Steady state experiments simulations
The results of the TrioCFD computations performed to simulate the experiments and will be first presented in a qualitative way through thermal fields and in a second time through comparison to the available experimental temperature data.
Discussion
It should be noted that the simulation results presented here have been obtained using a very basic model both from the point of view of the turbulence model and the turbulent thermal diffusion model used.
The turbulence model modified to take into account the effects of buoyancy and using standard parameters values seems thus capable of recovering the flow with sufficient precision whereas it is known not to be well adapted to flows presenting in particular expansions and constrictions
Conclusion
We performed four simulations of steady-state sodium mixed-convection experiments involving sodium obtained thanks to the SUPERCAVNA experimental device. These experimental results are typical of a wide range of mixed-convection flows varying from forced convection () to mixed-convection with a very strong diffusive effect ().
We used a RANS approach implemented in the TrioCFD computational tool and, despite the fact that the turbulence model is not a priory well adapted to the
CRediT authorship contribution statement
A. Genty: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. C. Roy: Conceptualization, Formal analysis, Investigation, Methodology, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. C. Geffray: Conceptualization, Formal analysis, Investigation, Methodology, Resources, Software,
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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