The Nuclear Regulatory Commission (NRC) is amending its regulations revising the NAC International, Inc., NAC-MPC cask system listing within the "List of Approved Spent Fuel Storage Casks" to include Amendment No. 4 to Certificate of Compliance (CoC) Number 1025. Amendment No. 4 will modify the present cask system design to incorporate vacuum drying enhancements under a general license. Specifically, the amendment will increase vacuum drying time limits, delete canister removal from concrete cask requirements, revise surface contamination removal time limits, and revise allowable contents fuel assembly limits.