Scientists at Oak Ridge National Laboratory (ORNL) have discovered a groundbreaking medical use for radioactive waste from the U.S. nuclear weapons program. They are repurposing Uranium-233, which has been stockpiled since the Manhattan Project, to extract a rare byproduct called Thorium-229. This isotope produces Actinium-225, a key ingredient in targeted alpha therapy, an advanced cancer treatment that delivers alpha particles directly to tumors while minimizing damage to healthy tissue. The therapy shows strong potential in treating cancers such as lymphoma, prostate cancer, and breast cancer. Although the global supply of Thorium-229 is extremely limited—only 45 grams exist—it is still enough to treat hundreds of patients each year due to the small doses required.
With the U.S. Department of Energy aiming to eliminate the entire Uranium-233 inventory at ORNL by 2028, researchers are working to develop new methods for producing Thorium-229. Since this isotope only comes from Uranium-233, alternative methods are needed once the current supply is gone. Scientists are investigating ways to create Thorium-229 by bombarding Radium-226 with neutrons in nuclear reactors, which changes its atomic structure. Another approach uses a particle accelerator, known as a cyclotron, to fire protons at Radium-226 or Thorium-232 to produce the desired isotope. These techniques offer a way to continue producing the material needed for cancer treatment without relying on legacy nuclear bomb-making substances.