NAC International (headquartered in Norcross, Georgia) provides three different dry cask storage options for spent nuclear fuel (SNF) located in the U.S. All three options are vertically-oriented systems that place SNF inside a metal canister and place the metal canister inside a concrete cask. NAC International is a wholly-owned subsidiary of USEC, Inc. (which also owns and operates the Paducah gaseous diffusion enrichment plant in Kentucky and is building the American Centrifuge enrichment plant in Ohio).
The Modular, Advanced Generation, Nuclear All-Purpose Storage (MAGNASTOR) system is the most current system available and it allows for dry cask storage of 37 SNF assemblies from pressurized water reactors (PWRs) or 87 SNF assemblies from boiling water reactors (BWRs). The MAGNASTOR system requires at least 4 years of SNF cooling time in a fuel pool prior to loading. The entire cask system is approximately 225 inches high (over 18 feet) and approximately 136 inches in diameter (over 11 feet), and weighs about 160 tons when loaded. The MAGNASTOR cask system has not yet been deployed in the U.S. However, 65 MAGNASTOR cask systems will be used in 2014 at the ISFSI for the Zion Nuclear Power Station, which is currently undergoing decommissioning.
The UMS technology was made available in the late 1990s, and it provides for both storage and transport of SNF. The UMS is capable of storing 24 SNF assemblies from PWRs and 56 SNF assemblies from BWRs. However, the UMS systems in place today in the U.S. at Catawba, Maine Yankee, McGuire and Palo Verde are storing only SNF assemblies from PWRs.
Prior to 1995, NAC International manufactured the MPC technology for storage of SNF. The MPC is capable of storing 37 SNF assemblies from PWRs and 89 SNF assemblies from BWRs. However, the MPC systems in place today in the U.S. are storing only SNF assemblies from PWRs and the canisters are filled with only 26 assemblies (at Haddam Neck) or 36 assemblies (at Yankee Rowe).
NAC International also supplied the first dry storage casks used in the U.S. for the PWRs at the Surry Power Station in 1986 — the NAC-I28 cask system. Two casks were deployed, each holding 28 SNF assemblies.
Additional information regarding NAC International can be found at the following website: