Abstract
A conceptual design of sodium cooled fast reactor as small-decentralized power supply has been performed. The reactor named 4S (Super Safe, Small and Simple) has a reflector controlled U-Zr metallic fuel core. Characteristics of the 4S reactor are non-refueling (core life time: 30 years), the negative coolant void reactivity during 30 years, integrated and simple reactor structure, and natural circulation decay heat removal systems. Accidents without scram events (AWS) as unprotected sudden loss of flow event and ATWS events have been analyzed for the passive safety features of 4S using a transient simulation code (ARGO-3 code). It is predicts that the passive safety can evade sever damages of the core and primary coolant boundary under the ATWS and AWS events.
