The U.S. Congress is looking into the security of its supply of medical isotopes, prompted by the recent Chalk River, Ont., nuclear reactor shutdown.

The facility, which provides two-thirds of the world's radioisotopes — nuclear material essential for medical imaging and diagnostic scans for fractures, cancers and heart conditions — was closed Nov. 18 due to safety concerns. It was restarted Dec. 16.

The U.S. doesn't make any of its own isotopes, importing most of them from Canada. However, politicians south of the border now want their top scientists to look into whether the U.S. should consider producing its own isotopes.

The National Academy of Science, a group of scientists based in Washington that advises Congress on a number of issues, has been asked to consider four questions — all relating to the supply of medical isotopes, and whether the U.S. should consider producing its own.

The options are expensive, says Naoko Ishibe, NAS program officer of the Nuclear and Radiation Studies Board in the Earth and life studies division of the National Academy of Science.

"It's hard to know if that's something the U.S. would want to fund, but with this recent crisis in Chalk River, there's a little more urgency in terms of not having that domestic supply," she told CBC News.

Dr. Sandy McEwan, president of the international Society of Nuclear Medicine, says the shutdown of the Chalk River reactor, concerns from the safety commission, and the government's legislation to have it turned back on have led to questions about the future of the government agency that runs the reactor, Atomic Energy of Canada Ltd.

"There is huge expertise and huge investment in Canada, and remember AECL reactors are marketed around the world, so anything that suggests there's a problem is a black eye for a major Canadian industry," McEwan said.

The recent battle between the government and the safety commission can't help, and neither can the ongoing problems with AECL's two reactors —Maple 1 and Maple 2 — both of which are years behind schedule and millions of dollars over budget.

McEwan said that if these reactors come on line soon, Canada can keep its dominance in this industry. If not, he said, the U.S. will begin to look elsewhere.