Assessment of SFR reactor safety issues. Part I: Analysis of the unprotected ULOF, ULOHS and UTOP transients for the SFR(v2b-ST) reactor design and assessment of the efficiency of a passive safety system for prevention of severe accidents

Highlights: • Innovative sodium cooled fast reactor concepts are investigated. • Newly conceived mitigation measures of the severe transients are being investigated. • Evaluation of severe transient behavior in sodium-cooled fast reactors is being performed. - Abstract: In the frame of an AREVA – KIT cooperation in the years 2008–2013 on R&D issues associated with Innovative sodium cooled fast reactor concepts, several major topics were identified as being of mutual interest to both partners, one of which was the evaluation of severe transient behavior in Sodium-cooled Fast Reactors (SFRs) and the impact of newly conceived mitigation measures. The SFR design taken for the analysis was the SFR(v2b-ST) reactor design, and the system code to be used was selected to be the SIM-SFR code. The transients chosen for evaluation of the efficiency of mitigation measures were the unprotected loss-of-flow (ULOF), the unprotected loss-of-heat-sink (ULOHS) and the unprotected transient-overpower (UTOP)