ROCKY FLATS, Colo. Plutonium, named for the Roman god of the underworld and the dwarf planet at the edge of the solar system, is one of the worlds most dangerous elements. Inhaling just one particle will bombard internal organs, particularly the lungs and liver, with harmful alpha radiation for decades. For the most part, it isnt naturally occurring. But until just over a decade ago, it was plentiful in this 5,000-acre patch of rolling hills and grasslands.

From 1952 to 1989, this picturesque sanctuary was home to a factory that produced plutonium triggers for nuclear weapons a lot of them. Nearly all of the approximately 70,000 nuclear weapons produced in the United States include a part made at Rocky Flats.

It was designated as a Superfund site in the early 1990s, and the radioactive materials have been removed. Its scheduled to open to the public for the first time next summer .

But rather than welcoming the prospect of thousands of new acres for recreation, some Coloradans are suing to stop it.