Reinforcing your shelter

Begin reinforcing your shelter from the inside by stacking dirt around the walls or anything else you can find. If in a trench, then create a roof, but only if materials are nearby; don't expose yourself when not necessary. Canvas from a parachute or tent will help stop fallout debris from piling on you, though it will not stop Gamma rays. It is impossible, at a very fundamental physical level, to completely shield from all radiation. It can only be reduced to a tolerable level. Use the following to help you determine the amount of material you'll need to reduce radiation penetration to 1/1000:

Steel: 21 cm (0.7 feet)
Rock: 70-100 cm (2-3 ft)
Concrete: 66 cm (2.2 ft)
Wood: 2.6 m (8.8 ft)
Soil: 1 m (3.3 ft)
Ice: 2 m (6.6 ft)
Snow: 6 m (20-22 ft)
7Plan on staying in your shelter for a minimum of 200 hours (8-9 days). Under no circumstances leave the shelter in the first forty-eight hours .[9]