The demolition on Friday of the cooling tower at the reactor complex in Yongbyon, North Korea.
From Yahoo News:
YONGBYON, North Korea - North Korea destroyed the most visible symbol of its nuclear weapons program Friday, blasting apart the cooling tower at its main atomic reactor in a sign of its commitment to stop making plutonium for atomic bombs.
An explosion at the base of the cylindrical structure sent the tower collapsing into a cloud of white and gray smoke that billowed into blue skies as international journalists and diplomats looked on, according to video footage filmed by international video news agency Associated Press Television News.
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News On North Korea From Other Sources:
North Korea destroys nuclear tower -- Times Online
North Korea Destroys Tower at Nuclear Plant -- New York Times
North Korea blows up reactor cooling tower -- Reuters
North Korea Says No To Nukes -- Pajamas Media
U.S. to Delist North Korea As Sponsor Of Terrorism -- Washington Post
N. Korea destroys nuclear reactor tower -- CNN
ANALYSIS-North Korea to reap benefits from South as ties thaw -- Reuters
My Comment: The original atomic scientists have always maintained a "doomsday clock", I can safely say that the clock will move back (a bit) from midnight after this North Korean gesture.