A comparative assessment of various single tray core catcher options for future sodium cooled fast reactors

Abstract

Various single tray in-vessel core catcher options to handle whole core decay heat for a 1500 MWt capacity sodium cooled Indian fast reactor (SFR) have been analyzed towards their efficiency in rendering acceptable core catcher temperatures. For this purpose, a one dimensional transient multiphase heat transfer model that considers sodium boiling, fuel particles re-melting and slumping has been adopted. The boundary conditions for the one dimensional model are obtained from computational fluid dynamics (CFD) simulations of turbulent natural convective heat transfer within the lower sodium plenum of the SFR. It is found that the top surface of the debris bed dissipates more heat than the bottom surface of the core catcher. A single plate core catcher is seen to experience melting of the core catcher plate (CCP) for a short duration in case of CCP thickness greater than 80 mm. The heat shield plate (HSP) of the double plate core catcher is observed to undergo complete melting due to vapor locking between the HSP and CCP. The phenomena of melting and slumping of debris particles is seen in double plate core catchers with a refractory lining. However, safe temperature levels of HSP and CCP were observed in the case of double plate core catchers with refractory lining. This study suggests that a double plate core catcher with a delay bed is the potential option for future sodium cooled fast reactors, which are to be designed to handle whole core meltdown scenarios.