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).