Plutonium is considered the most harmful known element, and is highly carcinogenic. The plutonium is used for research in the Halden reactor in Norway, according to the Klassekamp newspaper.
The head of the Institute for Energy Technology at the plant has confirmed the report that the plutonium is shipped out by air through Oslo's main airport.
"It doesn't happen often, the last transit was in 2011, and before it has happened about once every two years. All shipments are made in accordance with the regulations, which allows the use of passenger aircraft. So yes, we carry the passenger aircraft, as long as the airline considers it appropriate," Helge Valdseth told the newspaper.
Citing security concerns, Valdseth was however unwilling to indicate which airlines they use to transport the plutonium, confirming only that the regulations stipulated that a maximum of 15 grammes of fissile material can be carried per air shipment.
The practice is furthermore no problem for the Norwegian Radiation Protection Agency (Statens strålevern - NRPA).
"Transporting plutonium by air is within the rules and is problem-free," said Sverre Hornkjøl, a senior advisor at the agency, to Klassekampen.
Sverre Hornkjøl argued that it is no more dangerous to transport plutonium by air than by road.
"Not if you look at the accident statistics. There are more accidents on the roads than in the air," he observed.