A practical nuclear disaster protocol

Written by Shawn Buckles in Preparedness on February 28 2022

Some people take on a defeatist attitude when it comes to nuclear disaster survival rates. However, with some basic precautions and a simple protocol, most people will be able to survive nuclear disaster.

In this article:

  1. Understanding nuclear disaster
  2. Four life-saving priorities
  3. Supplies to have on hand
  4. Complete protocol
  5. Further preparations

Understanding nuclear disaster

In this first section, I want to quickly go through the basics of nuclear explosions. Once you know what to expect, I'll walk you through my step-by-step protocol.

Most people should survive nuclear fallout

Besides 'ground zero' — the immediate blast radius, ranging anywhere from 1 to 2.5 miles — anyone who is properly prepared should be able to survive an atomic bomb.

A 10-kiloton nuke would kill roughly 15,000 people instantly; 15,000 people would die due to the subsequential blast wave; and 250,000 people would die due to nuclear fallout, a 2004 Department of Homeland Security study found (Washington D.C.). Eight times as many people would die of fallout instead of the initial blast and radiation. Most properly-prepared people should be able to survive the fallout. Of the total 280,000 victims in this scenario, 93% could have lived.

Knowing how to act in this scenario will increase your survival rate tremendously. Of the initial 30,000 dead, 13,000 could have been saved by knowing to duck and cover. Simply laying flat will reduce your chance of being hit by debris from the shock wave eight-fold.

An atomic blast takes a while

I imagine air raid alarms will be sounding. An atomic detonation starts with a flash, which will be vibrantly white, and most likely intriguing to many. Our first impulse will be to stand at the window and see what it was. However, one should resist this impulse and duck and cover instead. Like thunder, it will take a couple of seconds before the air blast wave reaches you (5-20 seconds, based on your distance to the blast center). It will shatter any glass instantly and send it flying around like deadly razor blades, slicing anything in its way to pieces. As many people will die due to flying glass and debris generated by the air blast wave, as from the actual blast.

Radius of ground zero

Ground zero is the immediate blast zone, where the initial blast, fireball, and radiation will seriously endanger anyone inside (however, there are Hiroshima survivors which were at 300 meters from the blast, and subsequently grew old without any health issues, mainly due to having good cover behind concrete and steel). Personally, I define ground zero as the radius (r) that reaches over 10 psi (or 69 kPa), which is the pressure that severely damages all buildings and people.

Payload Ground zero (r in km) Ground zero (r in mi)
1 kiloton 0.4 1/4
100 kilotons 1.9 1.2
10 megatons 8.6 5.3

Download ground zero radius complete table (27.87 kB)

Within this zone, winds will approach the speed of sound at 300 m/s, or four times a category 5 hurricane. These numbers apply to an airburst, where detonation altitude has been optimized to maximize damage — air bursts will increase the overpressure radius dramatically, which means the radius will be lower in case of a surface blast.

As we can see from the numbers above, the immediate blast zone is limited, and doesn't grow linearly with larger yields: a 10-megaton bomb is 100x larger than a 100-kiloton bomb, however, it's blast radius is only 4.4x larger.

The average expected yield ranges from 50 - 200 kilotons for most targets, since most larger warheads fall within that range. There are warheads of up to 50 megatons, like Russia's Tsar Bomba, but I deem it unlikely that they will be used on ordinary targets.

Estimating our radiation exposure

Contrary to popular belief, the immediate radiation dosage outside ground zero shouldn't be critical. The amount of deadly gamma rays decreases exponentially as the radius increases, since the radiation will be dispersed over an exponentially larger surface area (inverse square law).

The initial radiation dosage of most nuclear blasts will be harmless outside an 1.5-mile radius (lower than 60 rems).

Deadliness of radiation exposure levels

Exposure of 60 rems or less is 100% survivable; exposure of less than 200 rems will be 100% survivable with medical attention. Above 200 rems, things get sticky. I've taken the data below from Wikipedia.

Radiation Survivability
< 60 rems no sickness
60-200 rems 50% sick
survivable with medical attention
200-1000 rems 50% will die within 2-4 weeks
>1000rems 100% will die within 2 weeks

Download critical radiation levels table (20.68 kB)

Rem stands for Roentgen equivalent man, and measures the health effect of ionizing radiation. 100 rem is equal to 1 Sv (sievert).

To estimate our potential exposure, we need to know two things you will most likely be able to get from an emergency broadcast:

  1. what is the blast yield?
  2. what is our distance to it?

Once we answer these two questions, we can compare them to the data below to get an idea of the levels of radiation we've been exposed to.

Tip: at the end of the article I'll link to more detailed tables for future reference. I've printed them out and put them in my nuclear disaster bag so I can quickly evaluate the shape we're in.

Radius of deadly gamma rays for different yields

Yield 1000 rem r 200 rem r 60 rem r
50 kt 1.5 km 1.8 km 2.1 km
100 kt 1.7 km 2.0 km 2.3 km
200 kt 1.9 km 2.2 km 2.5 km
1 mt 2.3 km 2.7 km 3.0 km

Download complete radiation radius table (33.38 kB)

This restricted radius means that even in crowded areas, most people will initially be spared deadly amounts of radiation; it is really the nuclear fallout that we need to concern ourselves with.

Nuclear fallout is radioactive particulate matter

Nuclear fallout is fine, radioactive dust: it will behave similarly to particulate matter. It has been generated in the nuclear blast, lifted into the air, and may take up to 15 minutes to come down again, only to cover the entire area in a thick, radiating coat of dust — though its radioactivity will dramatically and continuously drop. We want to limit our exposure to these particles by preventing contamination and putting distance between ourselves and it, especially during the first 24 hours. The goal is to keep fallout out of your shelter, and simultaneously create layers of radiation-blocking materials between yourself and the outside of your shelter, preventing critical doses of radiation.

Fallout radioactivity decays exponentially. The radioactivity of fallout will be worst in the first hour; 80% of radiation will be gone after 24 hours. 99% of radiation will be gone after 72 hours. Fallout radiation comes in the form of alpha, beta, and gamma radiation. Ordinary clothing will protect against alpha and beta radiation, so it is really the gamma rays we should concern ourselves with. To block gamma rays, we could build a shelter room, which we'll explore in the last section of this article.

Four life-saving priorities

Before we explore the logistics of nuclear disaster further, I want to touch on our priorities to maximize our chance of survival. With any nuclear explosion, our priorities are straightforward and non-negotiable. They are, in order:

  1. Cover: immediately, to minimize blast damage
  2. Shelter: within 15 mins, to minimize fallout radiation
  3. Evaluate: once shelter is secure, to assess risk
  4. Evacuate: whenever safe, or necessary

Failing any one of these will make all subsequent steps redundant, since each is critical to one's survival, which is to say our chance of survival will quickly diminish if we forget any. There are many steps to each priority, and there's much to know, which we'll all discuss below — but these are the four priorities I've made sure to etch into my mind.

Supplies to have on hand

Before we can implement our protocol, we'll need some basic supplies. The list below will run you about $100, which is well about worth it in my opinion. I'll spend it once and be prepared forever.

  • 1 gallon of water per person per day for at least 3 days
  • 3-day supply of non-perishable food
  • an emergency radio (battery or hand-cranked)
  • flashlight
  • extra batteries for both
  • dust masks to help filter contaminated air
  • duct tape and plastic sheeting to shelter in place
  • moist towelettes, garbage bags, and plastic ties for personal sanitation
  • wrench or pliers to turn off utilities
  • can opener for food (if kit contains canned food)
  • local maps

This should be your minimum kit contents, according to FEMA. Ideally, you should have a kit ready in all locations you frequent, including your vehicle.

I suggest adding the following items: radius maps of nuclear yields; distance table of frequented locations to potential targets. I also suggest carrying at least 2 weeks of water which will get you through any heavy fallout, and is also a more appropriate amount to stock for most other disasters.

Download nuclear disaster supplies list (28.93 kB)

Complete protocol

In case of a detonation, I recommend following this protocol:

  1. Duck and cover, cover ears and eyes and wait for the air blast to pass.
  2. Take potassium iodide as soon as possible if safe to do so.
  3. Get inside in under 10-15 minutes. The shelter should be suitable for 2-3 days.
  4. Designate a clean room (ie. hall) and take off your clothes, which could be contaminated; put them in a garbage bag and put them outside.
  5. Wash your hands.
  6. Close windows, doors, vents, fans, HVAC channels.
  7. Seal any broken windows.
  8. Take a shower to rid yourself of radiation; use soap, don't use conditioner.
  9. Start sealing up your shelter, work your way inwards, use plastic sheeting and duct tape.
  10. Retreat to the most inner part of the structure.
  11. Tune into the emergency broadcast.
  12. Don't drink tap water; wipe off food packaging before opening.
  13. Work any potentially contaminated items away from your shelter as far as possible.
  14. Take potassium iodide every 24 hours for the first three days. Save one dose for an evacuation.

I keep a printed version of this protocol in my disaster kit at all times.

Download nuclear disaster protocol (27.45 kB)

Preparation protocol

If you have time before detonation, do the following:

  1. Go to your shelter location;
  2. Open all windows and doors (will prevent them from smashing);
  3. Close all curtains, blinds, sunscreens, and so on;
  4. Take potassium iodide;
  5. Find cover behind a concrete wall, flat on the floor, face down; cover your eyes and ears and wait for the blast.

Initial cover

Get inside if possible. The less exposed you are, the better. Find the lowest point and lay on your stomach. The more concrete and steel is between you and any radiation, the better. If outside, cover your mouth with cloth; a wet coffee filter will do too (I carry one folded in my wallet). Avoid your car, being outside, avoid standing altogether, or looking at the blast, or being behind glass, next to doors, or in rooms where stuff will fall on top of you. Also avoid rooms with tiling — it will most likely fly around slicing things up after being shattered by the blast. Ideally, we put as much concrete, steel, dirt, between us and the blast. Go as deep inside a building as you can, but make sure it is structurally sound.

Prevent the urge to outrun fallout

Since levels of radiation decay exponentially, being inside during the first 24 hours is more important than getting away from the disaster zone. If you try to outrun fallout, you risk getting caught in it during these critical first hours. Vehicles do not protect from radioactivity in any meaningful way, thus dramatically increasing your chance of getting a lethal dose. Some shelter is always better than none.

How to seal your shelter properly

Immediately switch off all fans and seal off all vents. Then start sealing any windows with plastic sheeting and paper. Glass doesn't stop radiation at all, so getting the first layers in place quickly there is important. Next, seal off any gaps around doors and windows using duct tape. Then, close all curtains, window blinds, and sunscreens. The more fallout you can keep out, and the more layers you can put between yourself and it, the better. Once we have air-sealed our shelter, I'd start compartmentalizing the structure using plastic sheeting and duct tape. Work your way from the outside inwards as quickly as possible.

How to decontaminate

It's prudent to wash yourself in all nuclear disasters, but it is especially important after being directly exposed to radiation — if you got caught outside during the blast, for example. However, whether washing your hands or taking a shower, there are some important disclaimers. Firstly, you want to gently rinse; you do not want to rub your skin, since this will work in any radioactive matter. Secondly, you don't want to use conditioner, since this will bind any radioactive particles to you. Regular soap can be used. If you have no shower available, you may use wet wipes, but wipe lightly, and be sure to dispose in a garbage bag outside afterward.

People that have fallen victim to radiation sickness are unlikely to pose a threat to others; helping them will not make you sick.

Finding the safest location in your shelter

You want to retreat to the innermost part of your structure, putting as much distance between yourself and the fallout as possible. The safest location depends on many variables, but in most cases it will be the basement, if available, or else center of your structure, ideally encased in concrete, like a stairwell. The first floor will receive radiation from fallout on the ground outside, which means, when lacking a basement, the second floor could be better, depending on the wall and roof material surrounding you. I'll go into radiation shielding ability of different materials and thicknesses below.

Ideally you have a Geiger counter on hand to take the guess out of the equation, which would also be very useful if, for any reason, you are required to move within the first 48 hours.

Further preparations

In this last section, I'll briefly touch on some more advanced preparations you could consider. There are measures to be taken beforehand, some of them more costly than others, but all of them tremendously beneficial.

Additional items to have on hand

  • physical copy of nuclear survival manual
  • CB40 masks
  • Geiger counter
  • hazmat suits (activated charcoal military surplus) or regular disposable overalls
  • rubber boots
  • disposable gloves

Prepare your environment

We want to protect the structural integrity of our house as much we can. Protect your house from falling trees by chopping them down. Determine which room would be the safest in case of fallout, and prepare it as a potential shelter (more on that later). Start with taking down any potential falling objects. Make sure to keep physical copies of any information one would need at hand — chances are electronics will be toast or just temporarily unusable; also, it is easier to use and go through physical maps, sheets, and information when in a hurry or in a panic.

Designate a shelter, or build one

The principles of a shelter room are simple: you want thick walls in the center of your home, to put space between you and any radiation, debris, and so on. You can build a dedicated shelter room, or you can improvise one when necessary. In both cases, we need to determine the safest location, which requires us to understand how to block gamma rays. To estimate the required thickness of our radiation protection, we need to know the halving thickness of different materials.

Halving thickness of different materials

Material Halving thickness
Lead 1.2cm (0.5")
Steel 1.9cm (3/4")
Glass 2-4cm (0.8-1.6")
Concrete 6cm (2.4")
Plasterboard 7cm (2.8")
Brick 8cm (3")
Packed earth 9cm (3.6")
Plastic (acrylic) 11cm (4.3")
Wood 20-23cm (8-9")
Air 150m (500ft)

Download material halving thickness table (23.37 kB)

The sources for these data are Harvard Study and Wikipedia.

Nuclear fallout shelters typically use ten half-value thicknesses to offer good protection. Shielding is additive when combining multiple layers and materials. For example, you could use 10 cm of lead, which reduces gamma-ray exposure by roughly 1024 times. You could also use 60 cm of concrete, or combine multiple materials:

  • 36 cm of concrete (6 halving thicknesses)
  • 2cm of lead (2 halving thicknesses)
  • 4.2cm of steel (2 halving thicknesses)

But just 3.3 HVL (half-value layers) will absorb 90% of gamma radiation. This is called the tenth-value layer (TVL), and is a good goal for regular houses.

With these values, we can estimate the amount of radiation protection different rooms in our house provide, by adding up the layers of materials between us and the outside. I have made a map of my house detailing the radiation reduction of each room based on wall materials and thickness. We can also think up ways to increase radiation protection, by adding layers and materials to our shelter room. We could use sandbags and packed dirt, or stack up furniture against the walls. Anything that might help to absorb radiation could be put against the walls.

How to create a sensible contingency plan yourself

  • Print out the protocol and put in your emergency bag;
  • Print out the tables of ground zero radius, gamma-ray radius, and critical radiation levels;
  • Write down the distance to any likely targets in your area;
  • Create a radiation shielding map of your house to find the safest room;
  • Evaluate types of targets: military vs. civilian, ground vs. airburst respectively;
  • Evaluate likely fallout patterns: find prevalent wind directions, simulate fallout patterns from possible targets.

All of these documents will aid in evaluating your situation quickly, making hard decisions easier; for instance, whether a risky evacuation is necessary or not, and how to go about one. I keep all of these in my nuclear disaster bag. This way, when I get the critical information on the emergency broadcast (how large and where), I can immediately check whether or not we have been critically exposed or not.

If we have been critically exposed, or in case of particularly heavy fallout or a contaminated shelter, we should prepare an exit, but only after taking necessary precautions. Please note that exiting the fallout zone is extremely risky and a last-resort measure. We should first determine the quickest route out of fallout. For this, we need wind direction and speed. Then, we must wrap ourselves completely, take potassium iodide, put on a decent dust mask (FFP2 or ideally CB40), and move swiftly and decisively. If we can't get out of the fallout region quickly, there is no point in moving, since the amount of radiation you'll expose yourself to will be greater than when staying inside. A Geiger counter will be of great assistance in these kinds of situations, and I wouldn't go outside without one.

Print out all the datasheets in this article:

Questions I still have to answer:

  • Do fire blankets and survival blankets protect you? No
  • Are toilets and public water supplies a source of contamination? Can you flush, does it matter?

Further resources

Some good resources to learn more about nuclear explosions: