Radiation by the Numbers 3 & 7

Radiation by the Numbers 3 & 7

Radiation was a big buzz word back in the 50’s because every cheap Sci-fi movie had it being the cause of every type of mutant creature from giant ants on up. It then got batted around a little more seriously in the early 60’s in the era of the fallout shelters and the Cuban Missile Crisis.

However, as the Cold War reached a point where any nuclear exchange was expected to cause Mutually Assured Destruction (MAD), the interest in the basics about radiation and fallout faded.

But with nuclear power plant accidents and now the threat of terrorists using “dirty bombs”, explosive devices designed to scatter highly radioactive materials around the blast area, the word has returned in it’s frightening and often confusion form.

To help clear up some of the confusion here are a few point on the subject from the numbers 3 & 7, but first let’s talk about the difference between radiation and fallout.


Simply put, fallout delivers the radiation to you. Imagine fine sand falling outside, but in this case they are ash from what has been destroyed. That ash is now a tiny “X-ray” machine sending out its Alpha, Beta and Gamma rays. Keep in mind, fallout can be delayed and fall out of the upper atmosphere from distant places days later and be very fine dust that can be inhaled. (The delay in arriving will cause the radiation to decay in strength somewhat.)


TIME:  How long you are exposed. An exposure of 10 seconds or a minute, unless it is an extreme radiation level, may not be life threatening or cause you sickness. BUT such exposure should only be attempted in an emergency.

DISTANCE:  How far you are from the radiation. If the radiation is outside and you are in an inner room or hallway your exposure is much less than if you are standing by an outside window.

SHIELDING:  This is any barrier between your body and the radiation. This also varies with the type of radiation. A normal glass window is not very effective, but a wall is. Alpha and Beta radiation require less barriers to block than Gamma, which calls for 1-2 feet of earth, 6 or more inches of concrete, or lead. The general rule is the more you can put between you and the radiation source the better.

An inner room, storage area, closet or hallway with no windows as far as possible from the outside that you can get to within a minute or less provides an option.


Radiation generally decreases over the first 49 hours or basically 2 days. (7 x 7 hrs.)  This decrease continues over the next 2 weeks (7 x 7 x 7).  BUT in the case of a “dirty” bomb, the radioactive items used may be elements that will remain deadly much longer. Whenever possible remain sheltered until an official “All Clear”.


If you are exposed to 600 or higher rad units of radiation per hour odd are you’ll be dead in a day or so.

If you are exposed to 100-200 rad units per hour, you will be very sick and may not survive.

Now that’s an hour’s worth of exposure. If the rate is 600 per hour, a minute’s worth may be only 60 rad, bad but not horrible.

BUT the rate is cumulative in your body in the same manner as x-rays! That means if you get exposed to 60 rad per day, in a week you will absorbed 420 rad and will be in a bad way. If you are exposed in a 600 rad environment for 15 minutes you may have taken in 150 rad and may be sick.

In a terrorist “dirty bomb” incident, if you are out of the blast radius, get away as fast as you can from the area IF you are NOT in the path of the wind. If so, seek shelter inside a sturdy building or underground (subway) and await the all clear, or for authorities to help evacuate you.

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