A former International Atomic Energy Agency (IAEA) official cast doubts on a recent report estimating that North Korea’s stockpile of nuclear weapons could reach 100, potentially by 2020.

“It’s not a normal forecast, even in a worst-case scenario, that (North Korea) could build 100 nuclear weapons in six years,” former IAEA deputy director general Olli Heinonen was quoted as saying in an interview with Voice of America on Tuesday, referring to the U.S.-Korea Institute report North Korea’s Nuclear Futures: Technology and Strategy, authored by Joel Wit and Sun Yong Ahn.

“Building a nuclear weapon is a very complicated process,” Heinonen said. “Considering all the limitations, it is technically impossible to possess 100 nuclear weapons after five years.”

Heinonen worked for the agency for more than 20 years and led its investigations into nuclear proliferation networks, including one led by Pakistani scientist A. Q. Khan, who provided nuclear technologies to North Korea.

He said North Korea’s current capability for plutonium and enriched uranium production is at the level of building one or two of nuclear weapons in a year.

“Of course there is a possibility of (North Korea producing plutonium) in a unknown place but it needs an additional nuclear reactor,” Heinonen said.

He, however, agreed that North Korea is able to expand its stockpile without conducting additional tests.

“Tests are only required when you try to minimize and elaborate a nuclear weapon,” he said. “The one which was dropped on Hiroshima in 1945 wasn’t tested beforehand and the one on Nagasaki three days later had only one test.”

Picture: Olli Heinonen, IAEA Deputy Director General © European Union 2010