Pyongyang pulled out of the talks earlier this year. It also tested both a long-range missile and a nuclear explosive, in violation of United Nations sanctions.

VOA: standard.2009.10.10

North Korea pulled out of the talks earlier this year. It also tested both a long-range missile and nuclear explosive earlier in the year, in violation of United Nations sanctions.

VOA: standard.2009.10.05

The only other candidate as a nuclear explosive, enriched uranium, was (and remains) difficult to manufacture.

ECONOMIST: Glenn Seaborg

All of this helps to ensure that the nation will never have to return to nuclear explosive testing.

ENGADGET: NNSA Sequoia supercomputer takes worlds fastest title, prevents nuclear testing

"The application of such studies to anything other than a nuclear explosive is unclear to the agency, " the report says.

BBC: UN nuclear agency IAEA: Iran 'studying nuclear weapons'