 The fallout radiation was represented by measurements of the penetration of cobalt-60 gamma radiation, which has a high mean energy of 1.25 MeV (two gamma rays, 1.17 and 1.33 MeV).This is considerably more penetrating than the mean 0.7 MeV of fallout gamma rays.Therefore, the actual protection given against real nuclear weapon fallout would be far greater than that afforded in the peacetime cobalt-60 shielding measurements.