IN-GAS STORAGE METHOD AND IN-GAS STORAGE RACK FOR USED FUEL OF FAST BREEDER

PURPOSE:To execute in-gas storage of used fuel assemblies having a relatively high calorific value by storing the plural used fuel assemblies perpendicularly in a fuel storage cell and supplying a cooling gas forcibly into the wrapper tubes of the respective and fuel assembles from the lower part. CONSTITUTION:The inside of a fuel storage rack 11 and gas plenum 17 is segmented by perpendicular partition walls 19 to a core fuel storage chamber 20a for storing the core fuel of a relatively high calorific value, a plenum 21a for core fuel and a core constituting element 20b and core constituting plenum 21b for storing other core constituting elements. The cooling gas (gaseous argon, etc.) is supplied by each adequate volume via a flow rate regulating valve 33 into the core fuel plenum 21a and core constituting element plenum 21b of the gas plenum 17. The gas enters the inside of the wrapper tubes from lower entrance nozzles 13a and is returned through filters 34 to blowers 30. The used fuel assemblies 13 are, therefore, forcibly cooled from the inside by the circulating cooling gas and the in-gas storage of the used fuel assemblies having the high calorific value is enabled.