Abstract
The encapsulated nuclear heat source (ENHS) is a modular reactor that was selected by the 1999 DOE NERI program as a candidate <<Generation IV>> reactor concept. It is fast neutron spectrum reactor cooled by Pb-Bi using natural circulation. Decay heat removal system is the reactor vessel auxiliary cooling system (RVACS). Events of protected loss of heat sink (PLOHS) and unprotected transient over power (UTOP) have been analyzed for the ENHS using CERES a transient simulation code. It is confirmed that the ENHS core is sufficiently cooled by the RVACS under PLOHS condition. Under the UTOP condition, the inserted positive reactivity has been canceled by the negative reactivity feedback, the reactor power is maintained stable, in balanced the heat removal capability. The core is not catastrophically damaged.
