A transfer cask system for cooling spent nuclear fuel during the transfer from a spent nuclear fuel pool to a storage or transfer cask is disclosed. A canister containing spent nuclear fuel is inserted into a transfer cask. The transfer cask includes spacing components which define an annular region between the transfer cask and the canister. The transfer cask includes air inlets near a bottom end that permit air to flow through the defined annular region and exit at the open top of the transfer cask, thereby cooling the fuel within the canister. The transfer cask further comprises a neutron shield configured to absorb additional heat and shield radiation that may be generated within the canister. The transfer cask includes a transfer door that can open and close and has support rails that can support a spent nuclear fuel canister located in the transfer cask.