In response to the accident at the Fukushima Daiichi (1F) nuclear power plant, designers of the 2010 version of the Japan sodium-cooled fast reactor (JSFR) have been studying the robustness of JSFR's fuel handling system (FHS) against an earthquake and a tsunami. In the earthquake evaluation, the margin of seismic resistance and sloshing in the ex-vessel fuel storage tank (EVST) against an earthquake of the 1F-envelop condition were estimated. In the tsunami evaluation, for the case of loss of emergency power supply, a scenario is studied where fuel subassemblies are led to a stable cooling state, and potentialities for the cooling system are examined. As a result, it is shown that the original design of the JSFR FHS already had the potential to prevent the release of radioactive material. Additionally, some design improvements of the EVST cooling system are introduced.