A U.S. expert on North Korea says the North appears to be constructing a building for assembling and storing high explosive components of a nuclear weapon at its facilities in Yongbyon.
 
William Mugford, a researcher at the North Korea-focused Web site 38 North, analyzed commercial satellite images of Yongbyon taken on July 21, highlighting that the outside wall of the cells within a large new building has panels with a different tone and texture than the rest of the wall.
 
While acknowledging that they could be for decorative purposes, Mugford suggested that they could also be blow-out panels, which reduce the level of damage if a high explosive detonates during assembly or storage.
 
He said if they are blow-out panels, they would direct most of the energy outside the structure, so adjacent cells would not be damaged.
 
Mugford said construction at the experimental light water reactor is also continuing, adding the North appears to have finished the initial construction of the transformer yard at the light water reactor that will connect the electricity-producing reactor to the grid.
 
Mugford said, however, that the 5MWe plutonium production reactor at Yongbyon may not be operating or is only functioning at lower power levels, citing the absence of evidence such as steam or hot water discharge.