Within two weeks after an attack the occupants of most shelters could safely stop using them, or could work outside the shelters for an increasing number of hours each day. The longer fallout particles have been airborne before reaching the ground, the less dangerous is their radiation. Surrounding objects would reduce the radiation dose from these low-lying particles.įigure 1.2 also illustrates the fact that at a typical location where a given amount of fallout from an explosion is deposited later than I hour after the explosion, the highest dose rate and the total dose received at that location are less than at a location where the same amount of fallout is deposited I hour after the explosion. Weathering effects will reduce the dose rate further for example, rain can wash fallout particles from plants and houses to lower positions on or closer to the ground. If the dose rate I hour after an explosion is 1000R hr, it would take about 2 weeks for the dose rate to be reduced to I R/ hr solely as a result of radioactive decay.How long do you need to stay in before it's safe to come out? How would you know? A Nuclear bomb was detonated just 15 miles away but, thankfully, you were safe in your nuclear shelter.

Facts about the nuclear fallout shelter