Energy Northwest’s Columbia Generating Station has been in operation since 1984. Until 2002, all of the used fuel used in the reactor was stored in a specially designed, temperature controlled fuel pool. The fuel pool can accommodate a total of 2,658 fuel assemblies. It was designed with the understanding that the used, after six years of use in the station, would be transferred to a national repository, later identified as Yucca Mountain in Nevada.
In 1983, Energy Northwest and other U.S. nuclear utilities entered into an agreement with the U.S. Department of Energy wherein DOE would provide disposal service for discharged nuclear fuel, beginning on or before January 1998, for an annual fee. This agreement was established according to the Nuclear Waste Policy Acts of 1982 and 1999.
To pay for the national facility, utilities have contributed to the Nuclear Waste Fund a fee of one-tenth of a cent for every nuclear-generated kilowatt-hour of electricity used, amounting to many billions of dollars. Energy Northwest, alone, has paid over $100 million in fees since 1983. In spite of this effort, the goal of a national repository is nowhere near completion.
To date, DOE has spent $9 billion on the $58 billion Yucca Mountain project; however, due to the political sensitivity of the site, the repository has yet to materialize. The Energy Department had planned to apply for a Nuclear Regulatory Commission license by the end of 2004, but the date has been pushed back. DOE had earlier notified Energy Northwest and other nuclear utilities of an indefinite delay in fulfilling their contractual obligations. This dilemma has forced the nuclear industry to explore safe, alternative methods of storage.
Planning for Energy Northwest’s dry cask storage project, known as an Independent Spent Fuel Storage Installation (ISFSI), began in the late 1990s. Actual construction followed in 2001 to accommodate completion of the first dry cask campaign, encompassing the loading and storage of five casks in April 2002. Another campaign was successfully completed in 2004 with the loading and storage of another 10 casks, bringing the total to 15. Each cask holds 68 fuel assemblies, for a total of 1,020 spent fuel assemblies that have been offloaded from the fuel pool. The third campaign is currently under way and will add 12 additional casks.
Energy Northwest contracted with Holtec International of Marlton, New Jersey, the foremost dry cask manufacturer, for its MPC-68 canisters and HI-STORM metal and concrete storage overpack design. The base scope of the contract included design, licensing, and fabrication of 22 canisters and casks to meet Columbia Generating Station’s need for used fuel storage through 2010. The contract also included auxiliary equipment for loading, sealing, and transporting the canisters and casks to the storage site, as well as engineering support for the required site-specific safety evaluations.
Each concrete and steel storage cylinder stands about 19 feet tall and measures 11 feet in diameter. The outer cask encases a stainless steel canister that holds the spent fuel. Heat is transferred from the fuel to the canister walls by natural circulation of the helium gas in each canister. Between the canister and cask, there is a space to allow air to flow to cool the used fuel and canister. The casks rest on a large, two-foot-thick reinforced concrete pad located north of the plant in a fenced area protected and monitored by Energy Northwest security personnel.
The ISFSI provides safe and efficient storage of Columbia Generating Station used fuel until such time as it can be transported to a national repository. This solution will allow Energy Northwest to continue to provide inexpensive power to the region for many years to come.