Post-accident heat removal: Numerical and experimental simulation

Post-accident heat removal (PAHR) after severe accident in nuclear reactors plays a vital role to ensure public safety by effectively cooling fragmented core debris within the primary boundary. Design and implementation of multiple safety features demand thorough understanding of the sequences involved in accident progression. The key factors influencing PAHR are molten fuel coolant interaction and grid plate melt through, followed by relocation of fragmented fuel and structural materials settling on the core catcher in the form of debris below the core. The present work is focused on experimental and numerical investigation of melt fragmentation and settlement, morphological characteristics of debris, and finally heat removal from the debris bed via dedicated decay heat removal system. Series of dedicated experimental facilities have been setup in stages and preliminary trials are being conducted to generate the database for development and validation of numerical models, to be used for safety analysis of reactor systems. This paper also discusses preliminary experimental results and comparisons of data with numerical findings.