Operation Doorstop atom bomb test. Image 1 of 2. Mannequins in the living room of a wood-frame house built for atom bomb testing. Two houses were located 1100 and 2300 metres from the blast. During an atomic explosion, non-thermal radiation (gamma rays) is followed by a thermal pulse and then a blast wave. This test took place on 17 March 1953, at the Nevada Test Site, USA, as part of Operation Doorstop. This operation, supervised by the Federal Civil Defense Administration, included experiments to test the effect of an atom bomb on civilian areas. For the effects of the blast wave on the house and mannequins, see image C028/4091.