The U.S. Nuclear Regulatory Commission (NRC) is amending its spent fuel storage regulations by revising the Holtec International HI- STORM 100 Cask System listing within the "List of Approved Spent Fuel Storage Casks" to include Amendment No. 9 to Certificate of Compliance (CoC) No. 1014. Amendment No. 9 broadens the subgrade requirements for the HI-STORM 100U part of the HI-STORM 100 Cask System and updates the thermal model and methodology for the HI-TRAC transfer cask from a two dimensional thermal-hydraulic model to a more accurate three dimensional model. The amendment also makes editorial corrections.