Mythbusting: Nuclear Emergencies

Radiation is one of those threats that is universally feared, and for good reason. We spoke to nuclear Engineer Rick H. to separate the truth from the SciFi.

December 30, 2019
ISG Team


In our series on Mythbusting, we often tackle topics that inspire a great deal of fear... perhaps none is so insidious as radiation.

Nevil Shute's 1957 classic "On the Beach", brought the idea of inescapable, lethal radiation clouds to mainstream attention while war-weary populations grappled with the dawning 'Atomic Age'. The Doomsday Clock was ticking, and if Shute was correct, a nuclear war was nothing short of a death sentence for all life on Earth.

But how much of that fear is grounded in reality?

We consulted Nuclear Engineer, and former Submarine Captain Rick H. to discuss the myth surrounding radiation, how nuclear incidents impact the world we live in, and what we can do to better understand and prepare for them.

Radiation - The Science

The first, and probably most important thing to mention is that "radiation" isn't a single thing. Radiation is 'the emission of wave-form energy', which in and of itself, is pretty benign. Light is radiation, and, this might surprise you, but solar energy is the most damaging form of radiation you're ever likely to encounter. Why?

Well, the type of radiation we're worried about is "ionizing" radiation. Alone, it's really not much of a big deal. Ionizing occurs naturally when energy from an emitting particle disrupts an atom's electron cloud, which removes electrons from that atom and making it an unstable ion. When discussing inorganic stuff, ions aren't a big deal... however, in organic structures ionizing has three major effects:

  1. It kills the cell;
  2. The cell is able to repair itself and function more or less normally, or;
  3. The cell's mitosis process doesn't catch the error, and replicates the ionized cell structure.

Point 3 is the one people worry about the most, and we'll talk more about it soon, but for now, let's just say that a cell that replicates itself with errors probably will create more and more faulty cells - those masses become what we know as tumors... some of which can be cancerous.

With this in mind, let's discuss radiation as it relates to nuclear energy and weapons, so that we can better understand the risks stemming from nuclear emergencies.

Fission and types of Particles

Distilling one of mankind's most incredible achievements (managing the process of nuclear fission) into a few paragraphs is tough, but here's the basics:

Fission is the process of splitting larger, heavier atoms into smaller ones. Within an atom, nuclear forces bind the protons and neutrons together while electromagnetic forces push them apart, creating a stable balance between forces. When the nucleus of fissile material (those able to undergo nuclear fission, such as Uranium or Plutonium) are impacted by a neutron, it turns a moderately unstable, radioactive atom and turns it into an extremely unstable element that rapidly undergoes fission to split into more stable atoms (Krypton and Barium, though other combinations exist).

However, when Uranium undergoes fission, the added neutron takes mildly unstable 235-Uranium and makes the highly unstable 236-Uranium (for fractions of a second). This creates two stable atoms and 3 neutrons. Those leftover neutrons are the basis for ongoing fission chain reactions that create enormous amounts of energy, as they can continue to bombard the nucleus of other unstable 235-Uranium atoms for as long as there are Uranium atoms present. This is the basis for both weaponized reactions, as well as nuclear energy used in power plants..

Because this process is exothermic (gives off heat) process, energy is released as radioactive decay occurs.

During a uncontrolled reaction (or reaction that has become uncontrollable), there are a few ways we can be exposed to radiation:

  1. Unspent pieces of fissile material such as 236-uranium are ejected.
  2. Vaporized debris during a ground burst nuclear explosion and the subsequent ingestion or inhalation of radioactive particles
  3. Contamination of groundwater.
  4. Naturally occurring 'background' radiation, such as sunlight, radon, or mildly radioactive atoms within the body (Potassium-40)

These are just some basics, and we'll get more detailed below, but first better define radiation and how it affects us.

Ionizing Radiation

With a basic understanding of the types of ionizing radiation, we can further break down the emitters and their relative danger to our health during a nuclear emergency.


Alpha - The largest and highest energy emitters associated with radioactivity, alpha particles are extremely dangerous - but only if consumed. While Alpha particles emit a lot of radiation, it has a very limited ability to penetrate air, let alone skin. It's commonly said that while Alpha particles cause rapid radiation sickness if inhaled or swallowed, they can be stopped by a sheet of paper.

Beta - Beta particles are electrons that are emitted by radioactive atoms after a nuclear blast. Beta emitters can only penetrate about 10 feet of normal atmosphere, or about 1/8" of wood, water, or living tissue. The largest threat from beta radiation is inhalation or consumption in the immediate aftermath of a nuclear blast. If exposed to beta particles in the wake of an explosion, they may settle on skin or dust that is later ingested or inhaled.

Gamma Radiation and X Rays - Gamma radiation is emitted from within the nucleus of a radioactive atom, while microwave/x-ray radiation is emitted from outside the nucleus utilizing electrons. Both behave similarly, and are very high energy, with a great deal of ability to penetrate barriers. While it takes several feet of concrete or several inches of lead to block gamma radiation, they have no ability to irradiate tissues, and mostly pass harmlessly through living tissue.

Neutron - As the image above illustrates, the more dangerous particles have an inverse relationship with their ability to penetrate. That is to say, while Alpha particles are the most dangerous when they contaminate internally, they're the least able to penetrate. Neutrons, on the on the other hand, not only penetrate better than gamma/x-rays, but they have the ability to irradiate organic tissues.

Recall our discussion of fission, in which an unstable atom, such as 236-U splits to create 2 stable atoms and 3 neutrons. Those neutrons can be extremely dangerous components of a nuclear accident or blast. As a side note, neutron bombs are low yield nuclear warheads designed to minimize the blast damage, while maximizing the pulse of high energy neutrons. To unshielded person in the vicinity, the exposure would be lethal out to 900 meters, with probable radiation poisoning out to 1400m for anyone caught unprotected outdoors, making Neutron bombs a tactical nuclear device capable of causing very isolated effects (Kistiakovsky, 1978).

Neutrons within the Reaction

Given that Neutrons are so dangerous, you may be wondering "what happens to the ones that are left over?"

Well, in normal operations, engineers control the amount of fuel and water available to manage neutrons. As Rick tells us, neutrons come in two varieties: fast and thermal. The fast neutrons are too unpredictable to be useful, so engineers control their speed to bring them down to "thermal", where the cycle of fission can be regulated.

That's what we call criticality and it's a self sustaining relationship.
- Rick H.

Rick goes on to tell us that while accidents don't follow a form, a super-criticality can occur when the process isn't controlled and neutrons are generated too fast for a sustainable fission cycle. When this happens in a reactor, the process destroys the fuel matrix, which loses its critical geometry and ultimately stop the fission process.

When this happens, he says, the result is a mass of highly radioactive "slag" that decays while giving of beta and gamma waves, with less frequent alpha waves and occasional neutron events.

So while we see high profile events such as Fukushima's Reactor #3 as a major failure, it's important to remember that the containment cell actually did its job and contained the radioactive slag/Corium in spite of the meltdown. While Fukushima was undoubtedly a major regional tragedy, the engineers and facility did the best it could to minimize the overall effects.

As a side note, non-ionizing radiation, such as radio frequency radiation from Cell Phones, hasn't been linked to carcinogenesis in humans. While it may heat exposed skin, the radiation emitted by radio waves isn't ionized, and therefore can't really impact the cells in the ways necessary to cause cancers.

Contamination and Measurement

A Civil Defense CDV-700 Geiger Counter

Now that we've discussed the process by which ionizing radiation is created, and the types encountered in nuclear emergencies, we can discuss a couple things that are of particular importance to us:

  1. How to measure doses of radiation, and;
  2. The way we encounter radiological hazards.
Measuring Radiation

Measuring radiation is based on a couple things: The units being measured and the device doing the measuring. Typically, radiation is measured using either a Geiger Counter, or a Dosimeter, and like nearly all things nuclear, it can be broken down into parts:

Absorbed radiation is measured in:

  1. Rads
  2. Gray, which is the international equivalent of 100 Rads.

Whereas exposure is measured in:

  1. REM or Roentgen Equivalent Man (also used is milli-rem or mREM)
  2. Sieverts and milli-Sieverts

This leaves out several other measurements of radioactivity more generally, such as the Ci (Curie), Bq (Becquerel) , and R (Roentgens), which are also used.

The Nuclear Regulatory Commission says that in general,

1 Rad (exposure) = 1 Rad (absorbed dose) = 1 rem or 1000 mrem (dose equivalent).

We would add that:

1000 MilliRem = 1 Rem = 0.01 Sievert = 10 milliSievert

Which will help you when looking at the following image, which discusses the impacts of radiation (in mSv) on the human body. Given this, we can roughly convert the milliSieverts (of exposure) to Rads (of absorption) by dropping a zero. Keep that in mind when looking at the graphic in the next section.

Important note: Exposure is Cumulative.

Health Effects

Image shameless taxed from:

When we talk about the health impacts of radiation exposure, most immediately we think of two things: Radiation sickness, and Cancer, which pose the greatest threat from exposure to, and absorption of, ionizing radiation.

At Moscow's No. 6 clinic, which specializes in radiation treatment, a patient recovers after a bone-marrow operation. A doctor examines the patient in a sterile room. The examination is carried out in an individual, air-conditioned chamber via specially created openings to avoid direct contact and contamination. Source.

While quite a bit goes in to determining just how exposure will impact you, let's discuss radiation sickness which is the likely first step in assessing the casualties of a nuclear emergency.

Radiation sickness begins occurring after a few hours of exposure to radiation at 400 mSv levels, but it's important to note that often bursts of higher mSv exposure over *much* shorter timelines can also cause radiation sickness - so we have a function of time and intensity.

Typically, a person with the first signs of radiation poisoning are nausea, diarrhea, and vomiting. As symptoms progress, erythema (reddening of the skin) may occur if radiation was from an external source. Fever, disorientation, fatigue, headache, and blood in stool or vomit, and epilation (hair loss) are signs of advanced radiation poisoning.

Because radiation is invisible, if you don't have a geiger counter or dosimeter, it's nearly impossible to determine whether or not you're being exposed, and there's not much you can do as a preventative measure.

While Potassium Iodide (KI) tablets can saturate the thyroid, preventing the uptake of 131-I (a common isotope produced by nuclear disasters) it will not effectively block out any number of other radiological hazards. After the Fukushima incident, 131-Iodine, 134-Cesium, 137-Cesium were detected, so even with Potassium Iodide, you'd still have to worry about contamination from the Cesium isotopes as they decay. So while Iodine (and subsequent 131-Iodine) is a large component of the fission process (about 3% of the Uranium/MOX fuel matrix), the chances of being exposed to enough to make it worth while is very slim.

What about long-term health risks?

So what happens that makes radiation so deadly? In the instance of radiation sickness, it's the inhalation or consumption of charged particles. Once inside the body, there are no protective barriers like the skin to stop, or bear the brunt of, ionizing radiation. In this case, the particles essentially 'cook' you from the inside.

But what about the longer term risks?

As mentioned in the beginning, if ionizing radiation is absorbed in excess of what is 'normal', a person is at increased risk of cancer due to mitosis (cell division and replication) of damaged cells. The mRNA that encodes and translates proteins to DNA miscodes during the process of mitosis, which could happen thousands of times in a lifespan. This leads to masses of cells that are functionally useless, or worse, malignant.

In the aftermath of Hiroshima and Nagasaki, ongoing studies reported an increase of cancer related to the mutagenic effects of ionizing radiation... far and away the most common was leukemia, and predictably, it occurred most prevalently in those who's cells were most rapidly multiplying... the children.

Ongoing studies found that while the risk of Leukemia increased to as high as 46% for those living in the Hiroshima and Nagasaki areas, metastatic cancers (those that form tumors) didn't become prevalent until around 10 years after the attack, and were far less prevalent, affecting only about 11% of the population.

If you don't take anything else away from this section, take this note: Those who will be most affected by the crippling effects of radiation are children.

Therefore, if your threat matrix says you're at risk of exposure to a nuclear incident, you should have defined protective measures for children that include keeping them from ingesting or inhaling contaminated particles, and keeping them away from contamination sites.

Let's move forward to define contamination, fallout, and half-life.

Radiation Pollution Sources

Inside Reactor 2 of Fukushima Dai-ichi. This is the point of pollution. Seen here is the remains of the fuel matrix, taken April 2019. Source.

In addition to the immediate threat of exposure during an incident, we have to consider two more significant elements of the threat matrix: the half-life of the isotopes, and the contamination of the area surrounding the site of the incident.

Contamination typically manifests itself in three ways:

  • Point: A single, identifiable, and localized source of pollution. For example, Reactor 4 in Chernobyl, or Fukushima Daichi's Reactor 2 meltdown. These were the identifiable points from which the hazards came from.
  • Line: A source of pollution that emanates from a linear geometry such as a contaminated water line, or drainage ditch. Linear sources of pollution often occur along infrastructural lines, such as ditches, waterways, or roadways.
  • Plane: Pollution of this type exists when no single point can be identified as the source, but the hazard exists throughout. For example, while the site of a nuclear incident will be the "point" source, the area affected by particulates emitting ionizing radiation (radioactive fallout) would be a 'plane' source.

Similar to other contaminants, the effects of fallout is heavily dependent on a variety of variables... in the case of nuclear weapons, the 'ideal' situation is to have a "true airburst", in which the bottom of the fireball does not touch the ground, but detonates right above it. Failing this, a 'ground burst" explosion vaporizes and lifts tons of now-ionized debris that can be carried on the winds. This material can be deposited through rain or wind as a film of fallout that could cause contamination if touched.

With radiological incidences, it's entirely possible to have a point, linear, and plane of contamination. In the case of reactor failures, the contaminants rarely travel far, barring ocean contamination. In the case of nuclear weapons, the fallout's dispersal is based on complex aspects of weather and terrain.

Prevention: Fallout and Half-life. Not the video juegos.

Time, Distance, Shielding. Image lifted from Source.

So with a deeper understanding of what radiation is, how it works, and the potential threats to our health, what can we do if we live near a nuclear power plant, or a place of strategic importance? It's nearly impossible to have a 'fool proof' plan, but like most of our Type II and Type III emergencies, some basic provisioning and the ability to support yourself from home for a few months is mandatory. This means no food or water from municipal sources or grocery stores, so give that some serious thought. If there's time to evacuate, have a plan and a place to go. As we will discuss, the three basic ways to prevent exposure to radiological threats are...

  1. Time: One of the most important things regarding radiation that we haven't mentioned yet is the half-life of the decaying fissile material. The half life of an isotope is the duration it takes for it to become half as potent as it is at the onset of its radioactive decay. For this reason Every time a half-life period is concluded, it is half as powerful as during it's previous period. It's said that after 5 half-life periods, the radiation is said to be non-threatening.

    Here are the common half-lives and time required for common fissile materials to dissipate:
    90-Strontium: 28.8 years. Dissipation: 144 years.
    131-Iodine: 8.02 days. Dissipation: 40.1 Days/6 Weeks. (The body cannot distinguish from Iodine and 137-Iodine, and affects thyroid/hormone production. The wisdom of avoiding milk during fallout periods comes from this.)
    137-Cesium: 30.2 years. Dissipation: 151 years. (Highly soluble in water, and Cesium 137 ions easily affect tissues. Prone to linear source contamination.)
    235-Uranium: 703,800,000 years. Dissipation: 3,519,000,000 (Among the slowest decay known to man)
    236-Uranium: 2.86 Years. Dissipation: 14.3 Years.
    239-Plutonium: 24,110 years. Dissipation: 120,550 years. (Common in nuclear weapons)
    241-Plutonium: 14.1 years. Dissipation: 70.5 Years.
    243-Plutonium: 5 hours. Dissipation: 25 Hours.

    So, as you can see, nuclear incidents leave contamination that will be with us for generations, if it doesn't survive the human race entirely. Time may not be an option, but fortunately, some of the most prone to plane and linear contamination are the fastest to dissipate (131-Iodine and 236-Uranium).
  1. Distance: Next up, is distance. For those who were alive when Chernobyl was being forced under the rug, the Soviet strategy of "deny it happened" worked for a while because there wasn't much footprint outside the USSR (The soviet socialists republic, which collapsed so hard their teeth rattled, as socialist societies do). Ultimately, being away from the source of the contamination is an effective strategy. Similar to biological, chemical, or tephra based emergencies, wind fields and topographic play a massive role in how the contamination is dispersed. So, sorry Nevil Chute, "On the Beach" isn't possible. The prevailing winds prevent trans-equatorial dispersal of particles. No big, all-encompassing plume of radiation will wipe out all life on Earth (short of a gamma ray burst), so if you can, get some distance from the source of the contamination, and use some...
  2. Shielding: Even neutrons can be stopped by enough material obstructing their path. Shielding depends greatly on the type of emitter (as discussed above, Gamma will pass through more material, but are less able to damage tissues, whereas alpha emitters can be extremely dangerous, but you can stop them with a sheet of paper), but categorically, having a few feet of earth and concrete between you and the disaster will do tremendous things for the amount of radiation you absorb. This can be mitigated even further by having a way to filter your air, but when combined with distance and time, shielding can give even those very near the site of a catastrophe a fighting chance.

Threat from Nuclear Weapons

The aftermath of the bombing of Hiroshima
"...They were lucky it was me on shift that night."

The Cold War era of nuclear rivalry, mutually assured destruction, and 'duck and cover' drills have been replaced several times now with newer boogiemen. Muslim Extremists who hate your freedoms, Climate Change, and most recently, Active Shooters have all forced the threat of nuclear annihilation out of the public's mind.

But, chances are, if you're reading this from the United States, you've never heard of Stanislav Petrov, who averted a full-scale nuclear retaliation from the Soviet Union when their missile defense system mistook solar reflection off clouds for the launch of 5 minuteman nuclear warheads. Petrov reasoned that the system was likely a false alarm, and recalled that he thought there was a '50-50' chance it was a true crisis. His calm under pressure, rationalization, and 'instinct' spared the world what would have been a nuclear holocaust. any good soviet, he was reprimanded, and eventually retired to a life of obscurity, tending his ill wife (who died in 1997 from cancer) and growing potatoes to stay fed. While Petrov isn't the subject of this article, no conversation on nuclear war is complete without at least mentioning him, and the reality that no mass shooting or Muslim terrorists have power anywhere near that of world governments, and not all men in power are as level headed as Petrov.

Relative Calm

While there are unstable actors on the world stage who are armed with nuclear weapons, there is very little threat that they will be used by state actors. A larger threat from extremist groups using improvised nuclear weapons or those not repatriated after the collapse of the Soviet Union are more likely, but still represent a very distant threat.

Furthermore, the risks we face from nuclear warheads is much the same as those from nuclear accidents, with the subtle difference that refined fissile materials have more energy and therefore are more radioactive...

Nuclear weapons are a topic too big to cover completely in this article, so for now, check out the Oregon Institute of Science and Medicine's "Nuclear War Survival Skills". We will cover this topic in a separate article, but it will draw heavily on the material provided by OISM.

Nuclear Disasters

Pripyat, Ukraine

Far more likely, and empirically more common, are nuclear disasters. Much like mass shootings, when a nuclear reactor fails, such as the one in Nenoksa, Russia recently, or the highly publicized failure of Fukushima, people tend to fear the worst. The truth is nuclear energy is pretty safe, and the incidents are very rare. Of the worlds operational approximate 450 nuclear power plants, 2 have failed in the last decade - and I think we all might withhold judgment on Nenoksa until some things are declassified, as it's very likely that Nenoska was a weapons grade facility, the explosion there was an unconventional weapon, and the Russian silence on the matter is ...strategic.

The next question of nuclear disasters addresses something we have to consider: the long term ecological impacts.

Given that some of our radioactive materials take billions of years to fully decay, if there is a nuclear incident, how long before the land is once again safe?

There are three examples we can use to try and walk in our expectations:

  1. The Marshall Islands
  2. Hiroshima and Nagasaki
  3. Chernobyl Exclusion Zone

As with nuclear weapons, the ecology and biology of areas affected by nuclear incidents will require its own article. Briefly, however, these spaces tend to develop anomalous ecological changes, such as those in Chernobyl's "Red Forest"; an area in which the radiation was so lethal that it killed not only the trees and animals, but the bacteria and fungi as well. For decades, it has stayed in tact, without decomposing.

Conversely, Columbia University researchers said the following about Hiroshima and Nagasaki:

Among some there is the unfounded fear that Hiroshima and Nagasaki are still radioactive; in reality, this is not true. Following a nuclear explosion, there are two forms of residual radioactivity. The first is the fallout of the nuclear material and fission products. Most of this was dispersed in the atmosphere or blown away by the wind. Though some did fall onto the city as black rain, the level of radioactivity today is so low it can be barely distinguished.

If one thing can be stated for certain, it's that no two nuclear incidences are identical, and we have to be cautious with speculation or the assumption that we've got the situation well understood.


Through the course of this article, we've discussed the myth, fact, and uncertainty surrounding the nuclear emergency in a very general sort of way. While it's no longer the looming specter of global catastrophe it once was, nuclear emergencies are still around, and are still worth understanding from a scientific perspective, even if we can't know everything involved with that science.

While this topic is still complex, we hope that this article will  help you gain some understanding of how to think of ionizing radiation and separate it from the general term 'radiation', how Ionizing radiation affects the human body, and how it manifests itself as a contaminant.

If it has, please help us out by sharing this material.

If there are errors, please feel free to point them out - we strive for factual accuracy, but topics that require this level of detail often have slip ups.

As you may know, we believe in 100% accountability. That means if we're wrong and you catch it, we learn from you, too.


ISG Team


Kistiakovsky, George (Sep 1978). "The folly of the neutron bomb". Bulletin of the Atomic Scientists. 34: 27. Retrieved 11 February 2011. Recovered

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