http://angli02.kgw.tu-berlin.de/lexicography/data/MAVENS.html

Well this whole thing goes back to the debate over prescriptive ve descriptive "rules" of language. While it may be technically correct to pronounce "nuclear," many people obviously find "NOOK-u-lar" to roll off the tongue more easily. Since there is no lack of understanding on the listener's part, I don't see the problem, other than that heads of state are generally expected to speak more formally.