How much radiation is "a lot" and how much should I worry about?
April 11, 2017 at 11:14 pm #82641xsquidgatorParticipant
Given some recent interest and activity regarding nuclear war subjects over here, I’d like to share some information about radiation and radiation protection that may be helpful for the prepper and preparedness-minded person.
I’m writing this since radiation in one form or another has been part of my “day job” for the past 30 years, first in the US Navy (submarine nuclear power and later also a nuclear weapons guy), and for the past 20 or so years as a medical radiation therapy physicist. The information and opinion here is presented in the context of “this is one thing of many things that you might want to know about”, even though it’s not the most likely of doomsday scenarios compared to everything else that might happen.
Why should a preparedness-minded person know something about radiation? The possible situations that might arise include terrorism (“dirty bomb” or a nuclear device), nuclear war, nuclear power reactor accident, or simply just fear of an unknown. The goal of this piece and any follow-on pieces is to pare down a lot of the knowledge and information on the subject into useful bits. We’d also like to give you some appreciation of the “why” of radiation protection and not just the “how”. You should know some of the “why” so that you can make better-informed choices about what to do when the situation differs from what you planned for. We’re shooting for “greatly simplified, but accurate”. Chime in if you have opinions, we want you to have accurate info.
Let’s start by re-living something from recent history that I think everyone remembers and has maybe thought a little about- the 2011 Fukushima Daiichi reactor accident following a destructive earthquake and tsunami. Imagine that’s happening to an installation near enough to you that you’re worried about what’s happening, do you need to evacuate, what’s going on, how bad is it? If the news was reporting radiation levels at the site and other locations, would you know if the levels they’re reporting mean anything? If you have a Geiger counter of your own, and standing in your yard you notice it has started clicking twice per second, how bad is that? That’s a reasonable place to start, “how much radiation is a lot and how much should I worry about?”
Physical Effects of Ionizing Radiation
This is important, so that you have at least the principle in mind of how being exposed to ionizing radiation (alpha, beta, gamma, neutron radiation, as well as x-rays, electrons/protons/whatever else from medical or industrial radiation machines) affects you. Bear with this, the idea is important even if you’re not into chemistry, physics, or biology.
Ionizing radiation is called ionizing because it can ionize atoms with which it interacts, knocking off negatively-charged electrons from atoms as it goes by. Ions are chemically reactive and want to restore their electronic charge balance. Most radiation interactions inside our body occur with molecules of water, since we’re mostly made of water. These ions don’t last long (on the order of 10^-12 seconds) before they react with something and restore their charge balance, but this reaction can change the local chemistry of the volume where it takes place. If the little quasi-random radiation interaction occurs near a strand of a DNA molecule in the cell’s nucleus, the DNA itself can be changed. Sometimes the cell can fix the damage to the DNA, sometimes it can’t. If the damage to the DNA persists, the cell might remain unchanged, although with a mutation, it might die due to the error now implanted in it’s DNA. The changed DNA in the cell could cause the cell to function improperly and perhaps not stop dividing itself when it’s supposed to- this is one of the theories of how some cancers occur.
If enough chemistry in a small bubble of water inside a cell gets changed quickly enough, that cell may suffer some effects outside of whatever might be happening to the DNA.
So, the big picture here is that even a tiny tiny amount of radiation has the potential to cause a mutation or even a cancer. Greater amounts of radiation exposure and at higher intensities can cause acute damage to the cell that can make it not function properly, or can even cause the cell to die. If enough cells in one of your body systems are affected by radiation injury, you’ll feel the effects at some point and if it’s severe enough, you’ll get sick and could even die from it.
The effects of radiation also depend on how quickly you receive the radiation dose. Enough radiation received quickly can cause acute effects right away. If radiation dose is received over an extended period of time (say more than six hours, which is on the order of a typical cell division time more or less), cell repair mechanisms may be able to mitigate the damage and so a particular amount of radiation might cause less acute harm, if it’s given over a period of hours, days, or weeks versus all at one shot. But the risk of a long-term effect such as a mutation, or greater risk of developing cancer, may depend more on the total amount of radiation received than it does the dose rate.
Current practice in the developed world is to limit radiation exposures received by individuals to “as low as readily achievable”, and to not expose someone to ionizing radiation unless there is an offsetting benefit. I.e. if you’re in a car crash, the radiation risk of a CT x-ray scan is regarded as much less than the benefit of letting your doctor see if and what life-threatening injuries you might have. But, you wouldn’t go get that CT scan for just no particular reason as even the small radiation risk wouldn’t be worth it, for no benefit.
Units of Radiation
By “radiation”, we mean ionizing radiation such as gamma rays, beta particles or beta rays, and neutrons. A nuclear accident or nuclear attack can expose you to these from the explosion itself (if a nuclear weapon), or from the fission and activation products (basically radioactive dust particles) coming to you from the scene as fallout afterwards.
There are a number of units of measure for radiation, and there are even standard and metric units just like for everything else. For our purposes, the units of ionizing radiation are the “Roentgen” (symbol R), the “rad” (no symbol), and the “rem” (no symbol). These units are similar but not identical, for our purposes we can round them off simply as being the same for the types of radiation we’d get from the fallout from a nuclear attack or nuclear accident (1). So, 1 Roentgen is 1 R, which is also about 1 rad, which is about 1 rem.
(A) 1 R = 1 rad = 1 rem.
1 R, 1 rad, or 1 rem is a significant amount of radiation, so we may want to use “millirad (mrad)” or “millirem” (mrem). One mrem is one one-thousandth of a rem, or 1 mrem = 0.001 rem.
The metric or SI units of radiation dose (1, 2) are the Gray (Gy) and the Sievert (Sv). You should know these since many radiation measuring instruments now read out in these units instead of the traditional Roentgen, rad, or rem. Many state regulations nowadays have been converted into the SI units too.
One Gray = 100 rads, and one Sievert = 100 rem.
(B) 1 Gy = 100 rad
(C) 1 Sv = 100 rem
How much radiation? Natural background.
So what? Well, even in normal life right now, all of us are being exposed to radiation right as we’re reading this. Probably not “much”, but it’s there. There are cosmic rays from outer space hitting each of us. There is naturally-occurring radioactivity in the ground under our feet (about one part per million of the dirt under us is naturally-occurring uranium). If you live in an area richer in uranium ore, there’s more of that. The uranium gives off gamma rays, and also decays into radon gas which is radioactive and which can build up in unventilated spaces like basements. We have potassium in our bones, some very small fraction of which is naturally radioactive and thus emits beta particles and gamma rays.
In the U.S., the average person receives about 300-350 mrem per year from all sources of radiation, mostly cosmic rays, naturally-occurring radiation from around us and inside of us, and from medical radiation exposures. It rounds out more or less to 1 mrem per day, that’s what you receive right now just sitting in your driveway or in your house, with nothing going on.
(D) Natural background radiation ~ 1 mrem/day
How much radiation? Regulatory limits.
The next increment of radiation levels up from low, background levels, are the amounts of radiation that are considered to be safe for people to receive. Maximum radiation levels for members of the public (all of us) and for radiation workers are defined in both US Federal Regulations (in the Code of Federal Regulations or CFRs, such as 10CFR20) and in the regulations and laws of each state in the U.S. The US limits are pretty much in line with the limits set by other countries.
Current US regulations allow members of the public to receive no more than 100 mrem (0.1 rem) per year. Radiation workers (people who work in a radiation field, such as nuclear power plants, or medical or industrial facilities that use radiation) are allowed to receive up to 5,000 mrem (5 rem) per year. Most radiation workers receive far, far less than the regulatory limit.
So, even 5,000 mrem (5 rem) are useful guides to know- these levels are so low that really, nothing is expected to happen to you if you received it each year. It really doesn’t matter whether you received the 5000 mrem in a minute, an hour, or evenly distributed across the whole year, there are no acute (immediate) effects and not even any longterm effects of 5 rem.
For comparison, a medical computed tomography (CT) x-ray scan exposes the body part being imaged to about 1 rad or 1 rem of x-rays. A chest x-ray with modern equipment only gives you (on average) about 1-5 mrem (0.01 rem), and a dental x-ray only about 10 mrem. Older, less-modern x-ray equipment needed higher radiation doses to get the same quality image as we can get today.
By the way, this doesn’t mean that YOU get a ticket or something if you received more radiation than this. The entities (companies/institutions etc) which are licensed to have radioactive material or radiation producing machines are the ones who get fined or sanctioned if they expose you to more (non-medical radiation) than this. An ordinary person has no way to expose himself or herself to ionizing radiation which is probably a good thing given the proclivity for body piercings and tattoos recently.
How much radiation? Now things start to get interesting.
Let’s do a little thought experiment- you’re standing in front of a big x-ray machine with some mad scientist behind the panel, and we’re going to look at what happens as he gives you more and more radiation. From above, hopefully it’s clear that he could set the machine to “5 rem” and zap you with it, and you wouldn’t know it or feel it, nor would there be any apparent effect on you even if we took you to a medical lab and analyzed you.
Assuming you got the radiation dose in one shot or within a short period of about say six hours or less, the mad scientist would have to give you something like about 25 rads (25 rem) in a single dose, before even the most sensitive, state-of-the-art medical lab could begin to tell that something had happened to you. You wouldn’t likely feel any different, but at this point, your body will begin to feel the effects of that much ionizing radiation. Your blood-forming organs (blood marrow) are among the most sensitive to radiation, and at this point, would begin to produce less replacement blood for you. If nothing else happened, over a period of days to weeks, your blood counts (we’re simplifying quite a bit here but it’s the concept that’s important) would drop as cells in your blood die and aren’t normally replaced. If nothing else happens, over several weeks, your bone marrow should gradually recover, and you’d get back to normal. You might be just a tad weaker or more prone to infection, but probably wouldn’t feel anything.
-100 rem: Acute Radiation Syndrome
If the mad scientist keeps increasing the dose to you, at about 100 rem, you’ll actually get “radiation sickness” or acute radiation syndrome. By this level, it’s not just your blood forming organs that are reacting, but also others including your GI system. In addition to worsening blood forming organ function, the insult to the gut/GI system causes nausea, diarrhea, and other unpleasantness.
If all you receive is this one shot of about 100 rem and then you’re left to recover, you’ll be sick but could expect to probably recover in about 4-6 weeks, provided nothing else goes wrong and you’re able to rest and recover, stay fed etc. If not, you’ll be sicker for longer and you’ll be more susceptible to infections and other problems that could get serious in a post-SHTF situation.
As acute radiation dose increases above 100 into hundreds of rems, the damage gets more serious. Epilation (hair falling out, temporarily or permanently at higher doses) starts to occur. Skin changes start to occur in skin receiving these kinds of doses, including pigmentation changes (which can be permanent, like permanent tanning) and desquamation (skin breaking down).
-450 rem: LD 50/30
At about 450 rem, “Lethal Dose 50/30” is reached, this is the dose that is expected to kill 50% of the people who receive it, within 30 days. Same things going on as above, just more intense and the damage begins to cascade, becoming less likely to be survivable.
This LD 50/30 number has BIG error bars on it, meaning it’s not a hard and fast number. The lethal dose for people who are already sick or weak before the radiation will be lower than it would be for a young, strong, healthy person. The amount of medical care available also affects it- if you’re a single worker who is accidentally exposed in a workplace accident, but we can get you to ICU, your chances are perhaps better than 50/50. If half the people in your city of 500,000 people got the same 450 rem as you did though, everyone’s chances are probably a lot less.
There isn’t a lot of data on this, other than the Japanese A-Bomb survivors, survivors of various accidents such as Chernobyl, and some information we have from cancer patients who received radiation. From the Chernobyl cleanup experience, there’s some suggestion that LD 50/30 might lower than 450 rem.
1000 rem: lethal
An acute dose of this magnitude is effectively lethal, within a period of 1-2 days to a week. Louis Slotin (a Manhattan project scientist who died in an accident involving a bomb core) received about this much in one second, and died about a week later. The Chernobyl firefighters who responded a few minutes after the explosion and fire at the reactor plant received thousands of rem on the rooftop of the burning reactor in just a few minutes.
At doses of several thousand rem, the central nervous system (CNS) is affected and “CNS syndrome” can occur, resulting in disorientation, unconsciousness, and death before the other effects of acute radiation syndrome can happen. If you remember the “neutron bomb” nuclear weapon of the 1970s which was designed to be used against Soviet armored formations invading Europe, the doses it was intended to give to the target area were high enough to cause incapacitation by CNS syndrome.
Review: How much radiation?
All of the above numbers and information assume that the person’s entire body receives the same radiation dose at one go, an acute dose taking place in less than say several hours.
A person could receive the above radiation doses with less harm, if the dose were spread out over a longer time (say days, or weeks, the longer the better), or if just a portion of the body were irradiated instead of the whole body, the smaller the body portion the better. Also, the effect depends on which body parts get irradiated. Your extremities are generally less sensitive to radiation damage than the rest of you, and even US federal regulations allow a radiation worker to receive as much as 50 rem to an extremity each year compared to the 5 rem whole body limit.
To recap the above numbers, how much radiation?
1 mrem (0.001 rem) – about the amount of natural background radiation you get each day just being you.
100 mrem – the amount of radiation the government says is safe for you to receive from all other sources, each year.
5000 mrem (5 rem) – amount a radiation worker is allowed to receive each year
25 rem – A medical lab could just begin to be able to determine that something had happened to you, although you probably wouldn’t feel any differently.
100 rem- Acute radiation syndrome aka “radiation sickness”. Not good but if left alone under normal conditions, you’ll likely get over it.
450 rem- Lethal dose to 50% of population within 30 days.
How is this useful?
I think this information is most useful to someone who is trying to decide whether to “bug in” at home, or evacuate due to rising radiation levels. If the best information you have (we’ll talk about this later as it’s own topic) is that your area will receive at most only 1 rem or 1 rad in one week, well, that’s a lot more than you should get and it’s more than the government wants you to get, but as you can read above, it won’t hurt you that badly if at all. That might affect your decision to stay or leave.
Suppose you’ve sealed off and shielded your basement, have lots of food/water/comic books, and have measured the radiation level inside at a maximum of 1 mrem/hour. If it doesn’t go up, you could stay in there a looong time before having any kind of a radiation problem.
But, if you measure the radiation level in your safest place at 1 rem/hr (1000 mrem/hr) and it’s still going up, hopefully you can see that it’s probably time to leave and go somewhere out of the radioactive fallout plume.
There’s lots lots more to this, but, I think the above info is perhaps the best starting point to being able to think about how dangerous a particular radiation level would be to you in the next hour, 24 hours, the next week, whatever. Without some knowledge of how much radiation does what, all you’re left with is a bunch of mysterious scary potential death out there, and how do you deal with that?
Assuming there’s interest in this general nuclear “radiological controls for preppers” topic, some logical next things to talk about would be”
– Radiation measuring instruments for the prepper (what is a “Geiger counter”, how do you use it, how do you interpret the readings it gives you?)
-Radiation safety/control: how to use Time/Distance/Shielding to minimize your radiation exposure
-Radiation controls: avoiding/controlling internal exposure to radiation- ie- how do you prevent exposing your lungs/guts/internals from inhaling or ingesting radioactive fallout?
-Radiation controls- basic decontamination techniques, practices to prevent radioactive contamination of your safe space
-Nuclear scenarios- what kinds of radiation sources might I be exposed to if this or that happens? How much radiation?
Neat-O homework assignment-
Go to the NUKEMAP website, which is a neat nuclear weapons effects simulator.
The controls are on the right side, you put in any location, pick a nuclear weapon from the menu, and click the button to set it off and see the simulated effects overlaid on Google Earth.
Under option 3, click the checkbox for “radioactive fallout” and also click the box for “surface burst” vs “airburst” (surface burst creates a lot more radioactive fallout which is good for our teaching purposes)
Once you hit the “detonate” button and start looking at the map legend, you’ll notice some radii drawn on the map, including fireball radius, blast radius, etc. And there is a “radiation radius (500 rem)” drawn on the map. You now know what 500 rem is!
This is probably a good place to pause for now. Any thoughts/comments on this? Is this something of interest to some of the forum? Is this anticipating your nuclear/radiation concerns, does it make sense? Anything ya’ll want to discuss that isn’t listed above?
(1) The Roentgen is a unit of “exposure” and is the amount of x-ray or gamma ray radiation that produces 1 electrostatic unit of charge in 1 kg of dry air. 1 R = 2.58 E-4 C/kg.
A rad is a unit of “absorbed dose” of any radiation type in any material, not just x-rays in air. In air, 1 R = 0.87 rads which we round off to 1 R = 1 rad. Close enough for purposes of quickly determining if something is safe or not. “rad” stands for “Radiation Absorbed Dose”. Absorbed dose refers to the amount of energy delivered to a mass, specifically 0.01 J/kg.
A rem is a unit of “dose equivalent”, which is intended to quantify the relative biological effect of different kinds of radiation on humans. One rad of beta/gamma radiation is equal to 1 rem, hence we also round off or assume that 1 rad = 1 rem for the purposes of this discussion.
“Rem” stands for “Roentgen equivalent man”.
(2) The Gray is the SI unit of absorbed (radiation) dose. One Gray (Gy) = 1 J/kg. 100 rad = 1 Gy.
The Sievert (Sv) is the unit of dose equivalent. 100 rem = 1 Sv.
April 12, 2017 at 12:57 am #82642Joe (G.W.N.S.)Moderator
This is excellent work and thank you for your time.
Please continue as this will become part of the MVT Forum reference.
Go to the NUKEMAP website, which is a neat nuclear weapons effects simulator.
You can use “Launch multiple” to examine surrounding targets in your AO, before moving on to next launch be sure to check prevailing winds for your time frame (the flag pole can adjust wind direction) to guestimate the fallout threat.
April 12, 2017 at 6:57 am #82643Virgil KaneParticipant
April 12, 2017 at 6:58 am #82644
April 12, 2017 at 8:01 am #82645RobertParticipant
It’s important to have adequate measuring equipment. You will need to have a high level survey meter (a war meter versus a low range meter which could peg out during war time high rad count) and a dosimeter for each family member.
You will need those to be able to check to see if your distance and shielding is adequate.
The survey meter is like your car’s speedometer- it will tell you “how fast” things are moving right now. In other words, current rate.
The dosimeters operate a lot like your car’s odometer- they show accumulated radiation much like the odometer on your car shows accumulated miles. You will need this to KNOW what each person’s actual dose is. Not something you want to guess at.
Further, with each family member having a dosimeter and writing down their dose rate as well as current rates outside and inside the shelter, forecasts and planning can be better done. For example, let’s say Bob is late to get to the shelter. He traveled through some fallout but thought ahead and had this dosimeter on. He arrives at the shelter on Day 2 showing 50 rads accumulated.
Bob is NOT the guy that should go outside to clear the tree that’s fallen on one of the vent pipes if at all possible.
See how this info is useful?
Further- some common myths-
New “preppers” often get sold a bill of $hit with KI. I’ve seen dozens of places that sell that tell people it’s: A radiation “cure” or it “blocks radiation.”
KI is not a placebo, taking it is not going to make you “resistant” to radiation nor “cure” you of it.
It is designed to block one specific isotope on specific organ of the body. In other words, your not going to be able to take it and run out and make snow angels in the fallout like Ben Assfleck in “Sum of all Fears” (where he ran around in the fallout the later part of the movie like it was just super fun time).
You need to know all of the potential targets in your state and the states around you. You need to know general distances and directions to them. Valdosta and Moody AFB is 2 hours to the southwest. If Moody gets hit I know I have X hours (depending on wind and weather) before I start seeing first fallout. This needs to be in your mind, on your printed notes, etc. If you see/hear a blast you should note the time and write that down. Knowing you may have an extra hour or so, you might be able to shovel some more dirt in weak spots, move extra food and water, etc. Last minute stuff that does NOT include running to walmart for preps you should have been making now… :)
Great post thanks squid
April 13, 2017 at 7:45 am #82646HarrisParticipant
Fantastic informative post!
I work 2 miles from MacDill AFB so I would be ashes a few seconds after detonation!
April 13, 2017 at 5:12 pm #82647RobertParticipant
Fantastic informative post!
I work 2 miles from MacDill AFB so I would be ashes a few seconds after detonation!
You can always be banking any vacation/sick days at work. Then when things heat up in the world, take a day or two to “vacate” to a safer area for a day or two and call it a vacation.
April 17, 2017 at 2:19 pm #82648xsquidgatorParticipant
I’m working on a follow-on post regarding how to use your Geiger counter to measure general area radiation levels, and levels of loose surface contamination. Pic heavy. I have the pics and the captions written, just need to smooth the text out and then get the whole thing into a post.
The value of this little series will be mostly to convey the idea/information about how to do something and some background information. However, this is just a supplement to things like FMs or whatever is out there about WWIII and homeland security things. This supplemental material will hopefully clarify the reasoning behind the publications and procedures, so that you can adapt them to your situation with a bit more confidence.
April 17, 2017 at 3:47 pm #82649Short StrokeParticipant
Very helpful. Thank you.
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