OAK RIDGE, Tenn. — For decades Oak Ridge National Laboratory has been housing uranium 233. It was once a hopeful prospect as fuel for nuclear energy, but other resources were deemed to be better.

Uranium (chemical symbol U) is a naturally occurring radioactive element. In its pure form it is a silver-coloured heavy metal, similar to lead, cadmium and tungsten. Like tungsten it is very dense, ...

Oak Ridge Environmental Management office's Uranium-233 contract has been modified to allow the contractor to participate in a medical research arrangement, according to the office.