Abstract
The Hanford Site is a 560-square-mile (1,450-km2) complex established by the U.S. government in 1943 to produce plutonium for nuclear weapons, ultimately bringing an end to World War II. Plutonium production activities continued after the war through 1991, at which point the site's mission changed from plutonium production to environmental cleanup and restoration. Production activities at the site resulted in a broad range of contaminated materials and facilities, including 57 million gallons of high-level (i.e., highly radioactive) nuclear waste in liquid and solid forms. The high-level waste was stored as it was created, first in single-shell tanks built between 1943 and 1964, then in more robust double-shell tanks constructed between 1968 and 1986. Due to waste leakage in a small number of single-shell tanks and the potential for additional single-shell tank failures, all single-shell tanks were removed from service by 1980. All pumpable liquid has been transferred to sound double-shell tanks. The double-shell tanks have either exceeded or are expected to exceed their design life, and are managed under a comprehensive integrity management program. Key features of the program include the application and optimization of a waste chemistry specification designed to minimize corrosion in the double-shell tanks, laboratory studies, and the installation of double-shell tank corrosion monitoring systems to improve the understanding of waste corrosiveness, the development and application of an extensive non-destructive examination program to detect excessive corrosion or other forms of double-shell tank degradation should they occur, and the development and application of a comprehensive structural analysis program. Together, these programs help to ensure the continued availability of the site's double-shell tanks for the balance of the cleanup mission.
