debated whether the government should be in the electricity generation business. On November 28, 1961, the AEC reached an agreement with the Washington Public Power Supply System (WPPSS) for the latter to purchase its electricity. N Reactor was destined to be the last of its kind, but also had many new features as a product of 1960s technology. Its zirconium alloy-clad fuel slugs were long and in diameter. It had automated fuel-loading and unloading systems, a boron-ball scram system, and a state-of-the-art control room. It was the first American graphite-moderated power reactor, and the first American dual-purpose reactor, although other countries had them. The dual-purpose concept involved trade-offs that made both purposes less efficient: power required a steam turbine, but high water temperatures risked slug failure. The solution was to build a pressurized water reactor, in which the water was pressurized to allow it to remain liquid above . The reactor exceeded its original $145million budget (equivalent to $million in ) and cost $205million budget (equivalent to $million in ). The Hanford Site was now home to nine nuclear reactors along the Columbia River, five reprocessing plants on the central plateau, and more than nine hundred support buildings and radiological laboratories around the site. Extensive modifications and upgrades were made to the original three World WarII reactors, and a total of 177 underground waste tanks were built. Hanford was at its peak production from 1956 to 1965. Over the forty years of operation the site produced about 67.4 metric tons of plutonium, of which 54.5 metric tons was weapons-grade plutonium, supplying the majority of the 60,000 weapons in the U.S. arsenal. In 1983 and 1984, 425 kilograms of weapons-grade plutonium was extracted from reactor-grade plutonium. Tritium, polonium210, thulium-170, iridium-192, and uranium-233 were also produced. Decommissioning By 1963 the AEC had estimated that it had sufficient plutonium for its needs for the foreseeable future, and planned to shut down the production reactors. To mitigate the economic impact, closures were carried out over a period of six years. The change of policy was not publicly announced; instead, each round of closures was accompanied by a statement that production needs could be met by the remaining facilities. The first round of closures was announced by President Johnson on January 8, 1964. DR, H and FReactors were shut down in 1964 and, 1965. In 1967 the AEC announced that another reactor would be shut