Radioisotopes have potential for medical diagnosis

Of the thousands of radioisotopes identified so far, a few occur in nature, but most must be produced in nuclear reactors or particle accelerators. The most widely used medical radioisotope is technetium-99m (Tc-99m), the daughter isotope (meaning the product of radioactive decay) of molybdenum-99 (Mo-99).

The 66-hour half-life of Mo-99, which is currently produced by the fission of uranium targets in research reactors, makes it a challenge to produce and transport around the world before it spontaneously decays into Tc-99m. Built 30 to 50 years ago at the height of the Atoms for Peace era, several of the world's key nuclear reactors producing Mo-99 have experienced unplanned shutdowns that have disrupted the Mo-99 radioisotope supply.

With the possibility of an unstable supply, there is a strong incentive to develop alternative production methods for this essential isotope. To address this issue, the National Nuclear Security Administration (NNSA) is supporting commercial partners to accelerate the establishment of a domestic, commercial Mo-99 production capability that does not use highly enriched uranium.

At the same time, the NNSA is working to significantly reduce the risk of nuclear proliferation by supporting international Mo-99 producers in converting their Mo-99 production processes from highly enriched uranium (HEU) to low-enriched uranium (LEU). The U.S. Department of Energy's (DOE's) Argonne National Laboratory actively supports both of these efforts.

"Beginning in the 1980s, Argonne focused on converting targets for the production of molybdenum-99 from highly enriched uranium to low-enriched uranium and provided the technology to do so," said George Vandegrift, a Distinguished Fellow in the Nuclear Engineering Division at Argonne.

In the past five years, Argonne has partnered with industry and other national laboratories under NNSA stewardship to help establish U.S. production of Mo-99.

Now, in addition to continuing this technology development for Mo-99 production methods for the DOE and NNSA, Argonne is also advancing new production and processing approaches for other promising radioisotopes with the encouragement and support of the DOE Isotope Program.

Whereas Tc-99m, derived from its parent isotope Mo-99, is used primarily for diagnostic procedures, there is great interest in the development of efficient production methods for isotopes that can be used for cancer therapy. Argonne is using its recently upgraded electron linear accelerator (LINAC), along with its historical expertise in developing targets and recovering and purifying radioisotopes, to explore a variety of such therapeutic isotopes.

Argonne's electron LINAC operates in a "sweet spot" for making particular radioisotopes. At 30-50 mega-electron volts and relatively high currents, the LINAC has the capability to produce potentially important radioisotopes. For example, radioisotopes like copper-67 (Cu-67), and scandium-47 (Sc-47) -- whose use has been impeded in the development of pharmaceutical applications by lack of reliable supply or low specific activity.