1megaton is just little too
you do know the modern tactical nuke has a yield in in the 100's of Kiloton range. Most average 400-600kt range (which makes up the majority of most stockpiles)
especially the M.I.R.V. ICBMs and Cruise missile types
still much larger than Hiroshima (15Kt) or Nagasaki (21Kt), no where near the Test Munitions Like the U.S.S.R.'s Tsar Bomba with a yield of 50Mt (the U.S.S.R.'s Largest test could have reached 100Mt had they used a Depleted Uranium tamper instead of lead) or the U.S.A.'s Castle Bravo device at 15Mt (the U.S.'s largest test). the largest Active service US Device was the B53 nuclear bomb at about the 9Mt range but is now currently out of active service.
to me a anything larger than 1 megaton is a waste. (actually all Nuclear weapons are a waste (of money and resources) ) they are too horrible to use. and an unused weapon is a useless weapon. use the materials and Money to Put that crap to good use. build a series of Tokamaks and actually spend money on research and Development. For the love of god get me Fusion power in my life time