Review of design basis accident for large leak sodium-water reaction for PFBR

The design basis accident (DBA) for PFBR has been redefined in light of the PFR large leak sodium-water reaction incident. Study using the computer code SWEPT shows that 3 tubes failure at the top of the SG will be a new DBA. Parametric studies carried out indicate that SG with cover gas does not provide any advantage over non-cover gas design with surge tank for transient pressures due to sodium-water reaction. A study has also been carried out to see the effect of surge tank argon volume.