Preliminary transient analysis of the Autonomous Reactivity Control system for fast reactors

A preliminary parametric dynamic response study of the Autonomous Reactivity Control (ARC) system is performed for a large fast reactor core subjected to the following postulated design-extension accident scenarios: unprotected overpower (UTOP), unprotected loss of flow (ULOF) and unprotected loss of heat sink (ULOHS). The results show that the ARC system could prevent fuel and cladding failure as well as coolant boiling during UTOP and can lower transient temperatures during ULOHS. However, in case of ULOF, the design space examined the ARC system did not prevent exceeding permissible cladding temperature and introduced instability. A more thorough analysis is recommended.