When the Canadian government shut down a nuclear reactor in May, a group of physicians, scientists, and nuclear nonproliferation groups responded by petitioning to build one in the United States to generate molybdenum-99, an isotope used in medical tests to detect heart disease and cancer.

But there is still no consensus because of one disputed finding: Is the required material too expensive?

The shortage drove up isotope prices, which doubled in June and are expected to rise. The Ontario nuclear reactor produced one-third of the world’s and half of the United States’ supply of molybdenum-99, and it is unclear when it will come back online.

In their petition, supporters say the plan would ease dependence on foreign sources. The United States could potentially export some to other nations as well, though similar plans are underway in some European countries.

While nuclear-proliferation groups have typically opposed the medical community’s efforts to build a new reactor during past shortages, the situation is different this time, said Alan Kuperman, the director of the Nuclear Prevention Proliferation Program at the University of Texas-Austin.

“I think the petition could help significantly by demonstrating that there are no obvious opponents to the proposed solution,” said Kuperman, who drafted the letter.

James Ponto, a UI clinical professor of nuclear medicine, is one of those opponents. He said the National Academy of Sciences has been under “a lot of criticism” for the report.

“Most people believe the National Academy of Sciences really underestimated the costs [of using low-enriched uranium],” Ponto said.

It would take four to five times as much low-enriched uranium to produce the same quantity of isotopes currently made with highly enriched uranium. And the costs surrounding the reactors themselves are another obstacle. The petition suggests two options: upgrade an existing reactor at the University of Missouri-Columbia or build a new reactor — priced at $50 million and $250 million, respectively.

Location is also under dispute. Low-enriched uranium produces four times as much radioactive waste as highly enriched uranium. With no efficient waste-disposal methods, that means a possible 10 to 100 percent increase in costs could trickle down to the patient’s hospital bill, Ponto said.

“The usual view is ‘not in my backyard,’ ” said Michael Graham, a UI professor of nuclear medicine.

Graham said the shortage of the isotopes in past weeks forced his department to postpone several tests, such as those used to diagnose cancer and cardiac diseases.

The situation at UIHC is stable, at least for now. Graham said his department was able to secure an adequate supply of the isotope for this week — though officials don’t know if they’ll be getting another shipment next week.

“It’s kind of a week-to-week thing,” Graham said. “There are still a lot of uncertainties.”