List of Approved Spent Fuel Storage Casks: Holtec International HI-STORM UMAX Canister Storage System, Certificate of Compliance No. 1040, Amendment No. 1

The U.S. Nuclear Regulatory Commission (NRC) is confirming the effective date of September 8, 2015, for the direct final rule that was published in the Federal Register on June 23, 2015. This direct final rule amended the NRC's spent fuel storage regulations by revising the Holtec International, Inc. (Holtec), HI-STORM (Holtec International Storage Module) Underground Maximum Capacity (UMAX) Canister Storage System listing within the "List of approved spent fuel storage casks" to add Amendment No. 1 to Certificate of Compliance (CoC) No. 1040. Amendment No. 1 provides a seismically enhanced version of the HI-STORM UMAX Canister Storage System, identified as the "Most Severe Earthquake (MSE)" version that could be used in areas with higher seismic demands than those analyzed previously. Amendment No. 1 also includes minor physical design changes to help ensure structural integrity of the amended system. These are the addition of a hold-down system to the closure lid; replacing the fill material in the interstitial spaces between the cavity enclosure containers (CECs) surrounding the casks with 3000 psi concrete; strengthening the multi- purpose canister (MPC) guides, and engineering the guides' nominal gap with the MPC to be tighter than the original HI-STORM UMAX Canister Storage System design.