Radiation Basics

Hey Prepper Nation,

One of the most common Doomsday scenarios involve atomic weapons and the decimation of the population from thermal blasts and radiation.  Although the world has experienced nuclear blasts only twice, (Hiroshima and Nagasaki in 1945), nuclear events have occurred from time to time since then.   You have probably heard about the nuclear plant “meltdowns” at Three Mile Island (1979), Chernobyl (1986) and Fukushima last year.  A “meltdown” (technically known as a “core melt accident”) happens when reactor heat increases beyond safe levels, causing a nuclear element to exceed its melting point. This results in core damage.

Meltdowns and Radiation Exposure

Meltdowns usually occur as a result of failure of the nuclear plant coolant system.  This failure can occur as a result of damage caused by natural disasters, such as earthquakes or tsunamis.  They can, however, also be caused by human error or terrorist attack.  Regardless of the cause, the melted radioactive elements are released  into the atmosphere; this has serious implications for populations living both near and far from the event.

Radiation released into the atmosphere is known as “fallout”.  Fallout is the particulate matter (dust) that is thrown into the air by a nuclear explosion. This dust travels on the prevailing winds, and can travel hundreds (if not thousands) of miles downwind, coating fields, livestock, and people with radioactive material. The higher the fallout goes into the atmosphere, the farther it will travel downwind.  This material contains substances that are hazardous if inhaled or ingested, like Radioiodine, Cesium and Strontium.

Fallout and Long Term Health Dangers

Even worse, fallout is absorbed by the animals and plants that make up our food supply. In large enough amounts, it is hazardous to our health.  In an atomic bomb explosion, radiation is just one of the possible causes of casualties; thermal blast and kinetic energy damage near the blast will cause deaths and injuries close to ground zero.

A nuclear power plant meltdown is usually less damaging that a nuclear blast, as the radiation doesn’t make it as high up in the sky as, let’s say, a mushroom cloud from an atomic bomb. The worst effects will be felt by those in the area of the reactors. Lighter particles, like radioactive iodine, will travel the farthest, and are the main concern for those far from the actual explosion or meltdown. The level of radiation in an area depends on the distance that it has to travel from the meltdown, and the time it took for the radiation to arrive.  As the designated medic for your family or survival group, you should spend some time planning how to protect your people from exposure.

Henri Becquerel

To accomplish this goal, we should first clarify what the different terms for measuring the quantities of  radiation mean.  Scientists use terms such as RADS, REMS, SIEVERTS, BECQUERELS or CURIES to describe radiation amounts.  During the Fukushima event, you probably heard newscasters use several of these terms.  Different terms are used when describing the amount of radiation being given off by a source, the total amount of radiation that is actually absorbed by a human or animal, or the chance that a living thing will suffer health damage from exposure:

BECQUERELS/CURIES – these terms describe the amount of radiation that, say, a hunk of uranium gives off into the environment. Named after scientists who were the first to   work with (and die from) radioactivity.

RADS – the amount of the radiation in the environment that is actually absorbed by a living thing

REMS/SIEVERTS – the measurement of the risks of health damage from the radiation absorbed.

This is somewhat confusing, so, for our purposes, let’s use RADS.  A RAD (Radiation Absorbed Dose) measures the amount of radiation energy transferred to some mass of material, typically humans.  The medical effects of exposure are collectively known as “radiation sickness” or “Acute Radiation Syndrome”. A certain amount of radiation exposure is tolerable over time, but your goal is to shelter your group as much as possible.

Marie and Pierre Curie

An acute radiation dose (one over several days at the most)  is most likely to cause damage.  Below, you’ll find the effects on humans by the amount of radiation absorbed. For comparison, assume that you absorb about 0.6 RADs per year from natural or household sources.  These are the effects of different degrees of acute radiation exposure on humans:

  • 30-70 RADS:  Mild headache or nausea within several hours of exposure.  Full recovery is expected.
  • 70-150 RADS:  Mild nausea and vomiting in a third of patients.  Decreased wound healing and increased susceptibility to infection. Full recovery is expected.
  • 150-300 RADS:  Moderate nausea and vomiting in a majority of patients.  Fatigue and  weakness in half of patients.  Infection and/or bleeding due to a decreased  immune response. Medical care will be required  for some, especially those with burns or wounds.  Occasional deaths at 300 RADS exposure may occur.
  • 300-500 RADS:  Moderate nausea and vomiting, fatigue, and weakness in most patients.  diarrheal stools, dehydration, loss of appetite, skin breakdown, infection will be common.  Hair loss is visible in most over time.  At high end of exposure, a 50% death rate is expected.  Medical care is required for majority of patients.
  • Over 500 RADS:  Spontaneous bleeding, fever, anorexia, stomach and intestinal ulcers, bloody diarrhea, dehydration, low blood pressure, infections, and hair loss is anticipated  in almost all patients.  Death rates approach 100%.

The effects related to exposure may occur over time, and symptoms are often not immediate.  Hair loss, for example, will appear at 10-14 days.  Deaths may occur weeks after the exposure.

In the early going, your goal is to prevent exposures of over 100 RADS. A radiation dosimeter will be useful to gauge radiation levels and is widely available for purchase.  This item will give you an idea of your likelihood of developing radiation sickness.

There are three basic ways of decreasing the total dose of radiation:

1) Limit the time unprotected. Radiation absorbed is dependent on the time spent in the radiation. Leave areas where high levels are detected and you are without adequate shelter.  The activity of radioactive particles decreases over time.  After 24 hours, levels usually drop to 1/10 of their previous value or less.

2) Increase the distance from the radiation. Radiation disperses over distance and the effects will be decreased. To make an analogy, you have less chance of drowning the farther away you are from deep water.

3) Shield people to decrease radiation where they are. Shielding will decrease exposure exponentially, so it is important to know how to construct a shelter that will provide a barrier between your people and the source. A dense material will give better protection that a light material.

Barrier effectiveness is measured in “halving thickness”. This is the thickness of a particular shield material that will reduce gamma radiation (the most dangerous kind) by one half.  When you multiply the having thickness, you multiply your protection.  For example, the halving thickness of concrete is 2.4 inches or 6 centimeters.  A barrier of 2.4 inches of concrete will drop exposure to one half.  Doubling the thickness of the barrier drops it to one fourth (1/2 x 1/2) and tripling it will drop it to one eighth (1/2 x 1/2 x 1/2) the exposure, etc.  Ten halving thicknesses will drop the total radiation exposure to 1/1024.

Here are the halving thicknesses of some common materials:

Lead:                  0.4 inches or 1 centimeter

Steel:                  1 inch or 2.5 centimeters

Concrete:            2.4 inches or 6 centimeters

Soil (packed):     3.6 inches or 9 centimeters

Water:                7.2 inches or 18 centimeters

Wood:                 11 inches or 30 centimeters

Therefore, to take an example, if you are in a concrete bunker (2.4 inches halving thickness), you would need it to be 24 inches thick to drop your radiation exposure to 1/1024 of the outside environment.

Although many in the preparedness community don’t view a nuclear event as the most likely SHTF scenario, it’s important to learn about different causes for a collapse.  In future articles, we’ll discuss radiation sickness in detail and show you samples of protective shelters against radiation.

Dr. Bones


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4 Responses to “Radiation Basics”

  1. Tim says:

    Thank you for the well written post. My first exposure, as it were, to the basics of Radiation came from reading Pat Franks’ ‘Alas Babylon”. In my career as a firefighter Paramedic, I was certified as a radiological monitor and was tasked with supervision of our departments monitoring equipment.No real plans in place but we had equipment.  You mentioned halving thicknesses for shielding, but something else to factor in is the 7/10 rule where with every factor of seven increase in time, the radiation decreases by a factor of 10. I.E. 7 hours after a blast, the radiation is decreased to 10% of initial dose rate. 49 hours after the event, dose rate is 1/100 of initial, and so on. This is postulated on an isolated event.

    If you are concerned about measuring radiation, there is a meter design created by Cresson Kearny, who wrote “Nuclear War Survival Skills” which is a good reference source. There are also several venues that you can get film badge types of exposure meters or even pocket rate meters. 

    In my not so learned opinion, we might be more exposed to a dirty bomb or radiation dispersal sort of incident, instead of a nuclear detonation, or even contamination from Fukishima, Japan.

    • Dr Bones says:

       Hi Tim,

      You’re absolutely right about the 7/10 rule, which is actually in my next article of this series!  I also agree with your assessment of the likely scenarios in which we might be exposed.

      all the best,

      Dr. Bones

  2. Dave says:

    Urgent Warning: Fukushima Estimate of Situation

    Published on Apr 23, 2012 by NaturalSolutions

    Maj. Gen. Albert N. Stubblebine’s Personal Estimate of Situation



  3. Radiation Basics | Modern Homesteaders says:

    [...]  You can view this article in its original form HERE [...]

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