The Multi-Purpose Canister (MPC), conceptualized by the U.S. Department of Energy as a single versatile package equally suitable for on-site storage, transport, and permanent disposal in a future repository, was developed into physical embodiment by Holtec International in 1992.

The multi-purpose canister (MPC) consists of a cylindrical shell, the MPC baseplate, lid, port covers and closure ring which form the confinement boundary for the stored fuel assemblies. The confinement boundary is a seal-welded enclosure of all stainless steel construction. The MPC fuel baskets are composite cell structures made of stainless steel. The rectilinear honeycomb construction of the basket contained within the MPC provides for an extremely robust structural embodiment. There is complete edge to edge continuity between the continuous cells within the basket which provides an uninterrupted heat transmission path, making the MPC an effective heat rejection device.

The outer diameter and cylindrical height of each standard MPC is fixed, making them completely interchangeable. All MPCs fit the HI-STAR 100, HI-STORM 100, and HI-TRAC Transfer Cask equally well. The number of spent nuclear fuel storage locations in each of the MPCs depends on the fuel assembly characteristics.

Loading the spent nuclear fuel in a Holtec MPC is a final act; the fuel assemblies do not have to be repackaged ever again for subsequent handling, storage, transport, or disposal. In summary, the Holtec MPC has the following key characteristics:

  • An all-stainless fuel basket structure
  • A honeycomb geometry to maximize strength in anticipation of accident events
  • Fully edge-to-edge interconnected storage cells to maximize heat rejection
  • Top plenum, bottom plenum, and downcomers to maximize helium circulation (thermosiphon effect)
  • Evenly distributed metal mass to maximize shielding effectiveness
  • Identical external dimensions making them completely interchangeable (all MPCs fit the HI-STAR, HI-STORM, and HI-TRAC overpacks equally well).


TitleYearPatent No.Status
Fuel Basket for Spent Nuclear Fuel and Container Implementing the Same2023US 10,854,346 B2, 10-2039918, US 11,715,575 B2Granted
Nuclear Waste Storage Canisters, Welds, and Method of Fabricating the Same2022US 11,515,056 B2, CN ZL2016800621786Granted
Spent Nuclear Fuel Canister2022US 11,289,227 B2Granted
Manufacturing Methods to Fortify Nuclear Waste Canisters from Stress Corrosion Cracking2022US 11,250,962 B2Granted
Flood and Wind Resistant Ventilated Module for Storing Used Fuel Canisters2020US 10,878,973 B2Granted
Thermal Sleeve and Variable Vent Throttling to protect Used Fuel Bearing Canisters from Stress Corrosion Cracking in a Ventilated Storage System202063/043,812Pending
Heavily Shielded Unventilated Cask for Storing Nuclear Waste202062/969,183Pending
Treating the External Surface of Shell-Type Stainless Steel Structures to Protect Against Stress Corrosion Cracking201762/551,914Provisional
System and Method for Storing and Leak Testing a Radioactive Materials Storage Canister2016US 9,442,037 B2Granted
Container System for Radioactive Waste2016US 9,396,824 B2Granted