During the Cold War, the project was expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the 60,000 weapons in the U.S. nuclear arsenal.[2][3] Nuclear technology developed rapidly during this period, and Hanford scientists produced many notable technological achievements. Many of the early safety procedures and waste disposal practices were inadequate, and government documents have since confirmed that Hanford's operations released significant amounts of radioactive materials into the air and the Columbia River, which threatened the health of residents and ecosystems.[4]
The weapons production reactors were decommissioned at the end of the Cold War, but the manufacturing process left behind 53 million U.S. gallons (204,000 m?) of high-level radioactive waste that remains at the site.[5] This represents two-thirds of the nation's high-level radioactive waste by volume.[6] Today, Hanford is the most contaminated nuclear site in the United States[7][8] and is the focus of the nation's largest environmental cleanup.[2] While most of the current activity at the site is related to the cleanup project, Hanford also hosts a commercial nuclear power plant, the Columbia Generating Station, and various centers for scientific research and development, such as the Pacific Northwest National Laboratory and the LIGO Hanford Observatory.
