A Safety Enhanced Core Concept for Metal-Fuel Sodium-Cooled Fast Reactors

A safety enhanced metal fuel core has been developed that prevents fuel pin failure and coolant boiling during unprotected loss of flow (ULOF), unprotected transient over power (UTOP) and unprotected loss of heat sink (ULOHS) without relying on radial expansion reactivity.Specifically, we have enhanced inherent reactivity feedback and added passive shutdown devices without significantly changing core specifications and economic performance.The neutron flux distortion during UTOP situation with the control rod withdrawal and the neutron flux changes around the gas expansion module (GEM) during ULOF transient are also confirmed by improved quasi-static approximations.Both local neutron flux changes lead to a power increase, but even taking them into account, the inherent reactivity feedback and reactivity brought by passive devices in the safety enhanced metal fuel core are sufficient to prevent core damage under ULOF, UTOP and ULOHS conditions.