Numerical investigation of turbulent natural convection in the lower plenum of sodium cooled fast reactor under core relocation scenario

• Published in: Nuclear engineering and design Vol. 322; pp. 277 - 290
• Main Authors: David, Dijo K., Mangarjuna Rao, P., Nashine, B.K., Selvaraj, P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2017; Elsevier BV
• Subjects: Accidents; Boussinesq equations; Computational fluid dynamics; Computer applications; Computer simulation; Conservation equations; Containment; Convection; Convection cooling; Core catcher; Core meltdown accidents; Correlation; Debris; Decay; Decay heat removal in SFR; Decay rate; Energy conservation; Finite volume method; Fluid flow; Heat; Heat transfer correlation; Mathematical models; Post accident heat removal (PAHR); Radioactivity; Reactors; Relocation; Sodium; Studies; Turbulence; Turbulent flow; Turbulent natural convection; Velocity coupling; Post accident heat removal (PAHR); Heat transfer correlation; Core meltdown accidents; Decay heat removal in SFR; Turbulent natural convection; Core catcher
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2017.06.039

•Turbulent natural convection in lower plenum of SFR under core relocation scenario is numerically simulated.•Heat transfer coefficients are estimated from core catcher under PAHR condition due to TIB and ULOFA scenarios.•Correlations for Nu are developed for wide range of Bo∗ and are useful for the design of SFR core catcher.•Heat transfer coefficients during PAHR condition under ULOFA are lower than that under TIB. Turbulent natural convection inside the lower pool of pool-type sodium cooled fast reactor (SFR) is numerically studied for the modified Boussinesq number (Bo∗) range of 5×109 to 2×1011. The enclosure considered is a geometrical model of the lower plenum of a typical pool type SFR main vessel with the in-vessel type core catcher assembly. Aim of this study is to analyze the decay heat removal rate from horizontally spread core debris on the core catcher during post accident heat removal (PAHR) condition under core meltdown scenario in SFR and correlate the same with the associated non-dimensional parameters. The mass, momentum and energy conservation equations have been numerically solved in cylindrical co-ordinates using finite volume method and using SIMPLE algorithm for pressure-velocity coupling. Turbulence has been modelled using k-ε model and the computational model is validated against benchmark numerical and experimental studies on natural convection found in literature. PAHR has been simulated under two scenarios of decay heat removal (DHR), viz., under pump driven DHR condition above the lower plenum (i.e., under Total Instantaneous coolant Blockage (TIB) scenario) and under completely passive DHR condition (i.e., under Unprotected Loss Of Flow Accident (ULOFA) scenario). Nusselt number (Nu) is correlated as a function of Bo∗ for natural convection above the debris bed on the top surface of the core catcher and also below the bottom surface of the core catcher. These conservative correlations can be used in the design of in-vessel core catcher in pool-type SFR in order to ensure safe retention of radioactivity within the primary containment system even under whole core accident scenarios (WCA).