ON THE ESSENTIAL CHARACTERISTICS OF UNDERGROUND STORAGE OF SPENT NUCLEAR FUEL IN THE HI-STORM 100 SYSTEM

HI-STORM 100 is a vertical ventilated spent fuel storage system certified for use at any U.S. nuclear plant site under the rules of 10CFR72. The HI-STORM 100 System consists of a welded canister installed in a free-standing disposition inside a massive cylindrical body of steel and concrete, referred to as the “overpack” or the “ventilated module”, which is equipped with ventilation ducts near its bottom and top. The overpack can be deployed in a free-standing or anchored configuration. Although of a relatively stubby stature (approximately 11 feet in diameter x 18 feet tall with its lid installed), the aboveground HI-STORM 100 System is undoubtedly a conspicuous structure at a plant site. The underground version of the HI-STORM 100 overpack (labeled HI-STORM 100U), due to be certified by the U.S. Nuclear Regulatory Commission (USNRC) in early 2008, renders itself virtually inconspicuous by situating the canister underground. The depth of the canister’s location below the grade can be varied to suit the needs of a site, and the extent of physical protection provided to the stored fuel can be increased to the level desired by the facility’s owner by appropriately hardening the top lid, which is the only ingress path to the canister storage cavity. While the vertical ventilated module design undergoing certification by the USNRC is expressly engineered to store Holtec International’s canisters, it can also, in principle, be used to store other canisters in use around the world. In other words, HI-STORM 100U can serve as the universal vessel for storing all canisterized fuel in the world, making it a meritorious candidate for large autonomous storage sites such as the U.S. Department of Energy’s planned Aging Facility. The underground storage technology may also be particularly appealing to high seismic zone countries such as Japan and Taiwan, and in regions where nuclear plant sites are constrained by paucity of excess land or those located close to population centers, such as many in Europe.