There’s a mad dash for a vital radioactive isotope that’s used in about 50,000 medical procedures every day in the US, including spotting deadly cancers and looming heart problems. Currently, access to it hinges on a shaky supply chain and a handful of aging nuclear reactors in foreign countries. But federal regulators and a few US companies are pushing hard and spending millions to produce it domestically and shore up access, Kaiser Health News reports.

The isotope, molybdenum-99 (Mo-99), decays to the short-lived Technetium-99m (Tc-99m) and other isotopes, which are used as radiotracers in medical imaging. Injected into patients, the isotopes spotlight how the heart is pumping, what parts of the brain are active, or if tumors are forming in bones.

But, to get to those useful endpoints, Mo-99 has to wind through a fraught journey. According to KHN, most Mo-99 in the US is made by irradiating Cold War-era uranium from America’s nuclear stockpile. The US Department of Energy’s National Nuclear Security Administration secretly ships it to aging reactors abroad. The reactors—and five subsequent processing plants—are in Australia, Canada, Europe (Netherlands, Belgium, Poland, and the Czech Republic), and South Africa, according to a 2016 report by The National Academies of Sciences, Engineering and Medicine. Private companies then rent irradiation time at the reactors, send the resulting medley of isotopes to processing plants, book the final Mo-99 on commercial flights back to the US, and distribute it to hospitals and pharmacies.

With just a 66-hour half-life, Mo-99’s trip has to be fast. “It’s like running through the desert with an ice cream cone,” Ira Goldman, senior director of global strategic supply at Lantheus Medical Imaging in North Billerica, Massachusetts, told KHN.

But things often don’t go smoothly—or quickly. The international shipping can run into mundane travel delays. Jittery pilots may refuse to transport radioactive material. And then there are problems at the reactors. A curious baboon once wandered into the reactor hall in South Africa, causing an unexpected shutdown, for instance.

But a more common problem is maintenance at the reactors, some of which are more than 50 years old. Facing $70 million in repairs, the Canadian government decided to call off Mo-99 production at its Chalk River, Ontario, reactor in 2016. It will permanently shut down the reactor at the end of this year.

Decaying chain

And those disruptions and shutdowns mean shortages. In 2009 and 2010, there was a shortage of Mo-99 after two reactors went down at once. Doctors were forced to used more expensive, more toxic imaging agents. With the permanent shuttering of the Canadian reactor, the National Academies judged there to be a greater than 50-percent chance of impending “severe” shortages.

The imperiled supply and the ever-present concern of uranium getting into the wrong hands led President Obama to pass legislation in 2013 to push companies into the business of Mo-99. The handful of companies that have now risen to the challenge have received millions in federal funds to jumpstart efforts to make Mo-99 domestically and, importantly, without highly enriched uranium.

One of those is NorthStar Medical Radioisotopes of Beloit, Wisconsin, which received $50 million in funding and is working on a safe way to make Mo-99.

Likewise, SHINE Medical Technologies received $25 million from the DOE to help build a $100 million facility in Janesville, Wisconsin. SHINE got construction approval from the Nuclear Regulatory Agency last year and has designed eight particle accelerators for the site. They still need to raise additional capital and navigate a tangle of regulations.

But the company’s founder and CEO, Greg Piefer, a nuclear engineer, is optimistic. He promised the company will have Mo-99 production up and running by 2020, a deadline pushed back from 2015.

“If we don’t have significant production soon, we will continue to export highly enriched uranium,” Piefer said. “And the National Nuclear Security Administration will have failed their mission.”