*Nuclear Fallout Protection*
By: Mechanic
(11-01-01)

Nuclear fallout consists primarily of alpha, beta and gamma radiation. Alpha and beta radiation is easily stopped by as little as one inch (alpha) up to ten feet (beta) of air or by heavy clothing. In contrast, gamma radiation needs as much as ½ mile of air or 2 ½ feet of earth for proper shielding. Do not discount the danger of alpha and beta radiation just because it takes less shielding to stop it. Alpha or beta radiation can cause severe burns if left on the skin or ingested into the body through contaminated food or water.

There is no "one size fits all" formula for fallout protection. If you haven’t already done so the first step is to move away from target areas. Obviously you will fare better if your initial outside fallout rate is 10 r/hr than you will if the outside rate is 1000 r/hr.

Your goal in planning your shelter should be a minimum of PF 40 (a person inside your shelter will receive only 1/40 as much radiation as an unprotected person outside of the shelter). Children are more susceptible to radiation poisoning than adults so if you have children you will want to provide more shielding than what is needed for adults. Ideally, when you design your shelter you should have as much protection as you can provide but even minimal shielding is better than none at all.

Density is the key to radiation shielding. A pound of lead is a thousand times more effective than a pound of feathers. The following table gives the amount of material necessary to reduce radiation exposure by one half (one, "half-thickness").
Steel - 0.7 inches
Concrete - 2.2 inches
Earth - 3.3 inches
Wood - 8.8 inches
Water - 4.8 inches

When figuring your fallout protection factor be sure to use the totals of all the insulating material. For instance, if your shelter roof is made out of 4 inches of concrete and you have two feet of earth on top of the concrete your protection factor is 9.0 half-thicknesses. (4.0 divided by 2.2 equals 1.8, 24 divided by 3.3 equals 7.2, 7.2 plus 1.8 equals 9.0) Remember, each half-thickness reduces your radiation exposure by one half [so 2.2 inches of concrete reduce your exposure by 1/2. 4.4 inches of concrete (two half-thicknesses) reduces your exposure by ¾. 6.6 inches of concrete (three half thicknesses) reduces your exposure by 7/8]. The easiest way I know to understand this is to use a table of "half-thicknesses."

If you don’t want to do the math the following table will give you an idea of what’s required to stop 99% of most radiation.
16 inches of solid brick
16 inches of hollow concrete blocks filled with sand
2 feet of packed earth (3 feet if loose)
5 inches of steel
3 inches of lead
3 feet of water

Remember that the roof of your shelter will need to support the shielding material. The chart below gives the weight (in pounds) of some common materials used for radiation shielding. (One square foot of area covered to a depth of four inches.)
Sand - 35
Wood - 10
Water - 21
Cinderblocks - 22
Bricks - 32
Solid concrete blocks - 45
Books - 15

Shielding is only one aspect of your fallout protection. Don’t forget some other essentials such as ventilation, water, food, sanitation, sleeping arrangements, entertainment, lighting, communications, medical needs, radiation monitoring and decontamination. It would also be wise to try out your shelter arrangements before you need them. If you think you’ll just dig a hole in the yard, throw a door over it and cover the whole thing with dirt then try shutting your entire family into one small room for 48 hours straight (while toilet needs are taken care of in a bucket in the corner). You will soon see the wisdom of constructing your shelter in advance with care and planning.

All materials at this site not otherwise credited are Copyright © 1996 - 2001 Trip Williams. All rights reserved. May be reproduced for personal use only. Use of any material contained herein is subject to stated terms or written permission.