Researchers at IHS Jane's Defense Week told The New York Times earlier this year that North Korea was progressing with the construction of a light-water uranium reactor. Enriched uranium could find its way into the North Korea nuclear arsenal, though the country's first nuclear tests were believed to have used plutonium devices.
The Korean Broadcasting System reported that it secured satellite imagery from nuclear facilities that indicate a dome-shaped roof is covering a reactor in Yongbyon and work was apparently completed on the outer part of the facility.
This week, the U.S.-Korea Institute at Johns Hopkins University said information gleaned from commercial satellite imagery suggests North Korea has tested at least two rocket motors as recently as September.
North Korea was criticized in April for trying to deploy a long-range rocket into orbit despite assurances it wouldn't carry out nuclear of missile tests. Similar launches in 2006 and 2009 coincided with tests by the North Korean government of nuclear devices.
In October, Pyongyang said it has missiles in its arsenal that could strike the U.S. mainland and its strategic interests in the region.