Deleted member 1487
Apologies, I shouldn't have said blast radius, I mean blast effect; it would clearly not have been a 4km fireball. I was thinking more of the overpressure/heat effectSorry to burst your bubble but i'm pretty sure this is a complete hoax. The russian FOAB (the biggest thermobaric weapon ever tested) only had a blast radius of 300m (compare the 150m radius of the American MOAB) with a weight of 7 tons.
Actually a 4km fireball radius would be the equivalent of the fireball radius of the Tsar Bomba...