Just ahead of the second shutdown of a nuclear reactor that produces medical isotopes, Covidien (NYSE: COV) announced a deal with Poland’s Institute of Atomic Energy to begin importing Molybdenum 99.

The isotope, used to create the medical isotope Technetium 99m used in imaging procedures, has been in scarce supply since the shutdown for repairs of the Canadian reactor that produced a third of the global supply in May 2009. A second reactor in the Netherlands is also slated to shut down for repairs Feb. 19, meaning already scant supplies of Mo 99 are about to become even rarer.

The Covidien deal is still subject to international approvals (requiring 20 permits from five countries in Europe, according to the New York Times) and the Food & Drug Administration still must review samples from Poland’s Maria reactor before allowing it to be used on patients.

Mansfield, Mass.-based Covidien said once all the regulatory hurdles are clear, the deal will help “meet the needs of more than one million additional patients” in the six months following the first importation of Polish Mo 99. Covidien pharmaceuticals division president Timothy Wright said the deal is the first in decades to bring a new reactor producing medical isotopes into the global supply chain.

The company is the second with roots in the Bay State to seek to alleviate the Mo 99 shortage, following Billerica-based Lantheus Medical Imaging Inc.’s arrangement last summer with an Australian reactor to import the isotope.