A system dynamics analysis is applied to a pool-type fast breeder reactor to examine the influence of a bottom-supported reactor vessel (BSRV) design on anticipated transient without scram (ATWS) events such as an unprotected loss of flow (ULOF), an unprotected loss of heat sink (ULOHS), and an unprotected transient overpower (UTOP) by using the ARGO safety analysis code. The BSRV enhances negative feedback because of the differential displacement between the core and the control rod as compared with a top-supported reactor vessel. In particular, the BSRV has the potential, especially in a mixed-oxide-fueled core, to mitigate the design requirements to prevent boiling of the coolant during an ULOF and ULOHS through the elongation of the primary flow coastdown and enhancement of the axial expansion of the control rod drive line. In the metallic-fueled core, the effects of the BSRV on the ATWS events are diminished by the limitation of the sodium temperature increase.