Seaborg and the AEC projected the growth of nuclear-powered electricity would be so great that global supplies of uranium would be exhausted, paving the way for the recovery of plutonium from spent power reactor fuel for the next generation of power plants, which would dot the global landscape. Seaborg estimated by the end of the 20th century, power reactors would cumulatively produce 1,600 metric tons of plutonium with the potential to fuel half the nation’s electrical generation.
As of the end of 2018, US spent power reactor fuel contained about 824 metric tons of plutonium—the world’s largest single inventory of that element. The intense radiation of used nuclear fuel assemblies makes them essentially impervious to theft or diversion to weapons use. But after 300 years, a great deal of the radiation barrier protecting them will have decayed. The Nuclear Waste Policy Act lays out a process for geologically directly disposing of spent nuclear power fuel in an underground repository, rather than allowing plutonium to be separated from it. Reprocessing “would incur a substantial cost penalty,” concluded an industry study in 2006 and would be far more costly more expensive than direct spent nuclear fuel disposal. “[Re]processing would have to be accompanied by deployment of fast reactor plants. But demonstration fast reactor plants to-date has mostly proved expensive and unreliable, which aggravates [re]processing’s economic handicap.”
By the mid-21st century, the amount of plutonium in spent power reactor fuel could grow to more than 1,400 metric tons. The 300-year clock measuring off the time until the radiation barrier diminishes to the point that this vast amount of weapons-usable plutonium can be readily obtained is still ticking.
Read more at The long-term problem of “peaceful” plutonium