Study of alkaline carbonate cooling to mitigate Ex-Vessel molten corium accidents

•Heat absorption from carbonate mineral decomposition can be used to quickly solidify molten corium and mitigate an accident.•This injectable granular material concept can be integrated into an existing nuclear power plant accident management system.•MELCOR was used to demonstrate the effectiveness of the novel injectable mitigation system in a simulated reactor accident.•The MELCOR analysis demonstrates that using this carbonate injection system can delay the destructive hydrogen explosion.