The Nuclear Regulatory Commission (NRC) is amending its regulations revising the NAC International, Inc., NAC-UMS cask system listing within the "List of Approved Spent Fuel Storage Casks" to include Amendment No. 3 to Certificate of Compliance (CoC) Number 1015. Amendment No. 3 modifies the present cask system design to add an alternate poison material, revise the structural analysis, revise the thermal analyses, revise fuel assembly weight and dimensions, and revise allowable fuel cladding temperature. The amendment also revises the criticality analyses and reorganizes the Safety Analysis Report (SAR) Criticality Section, revises Technical Specification A.5.5 to remove the effluent reporting requirements, and makes several editorial and administrative changes.