Nuclear Preparedness Guide

Author: Finan Adamson

Last Updated 03/​2022


This doc is to help you prepare for the tail risk of nuclear war. Estimates vary, but an EA Forum survey put the annual probability of US-Russia nuclear war at 0.24%. This doc will go into some detail on threat models of nuclear war and then go over preparations you could make to survive being near a nuclear event.

Threat Models

Nuclear Bombs

To get a sense of how a nuclear bomb damages an area, the distance of radioactive fallout, etc. you can check out NukeMap. The damage caused by a nuclear bomb or missile being detonated is going to depend on many factors including bomb size, detonated on ground or in air, weather, etc. This chart includes some distances and effects for different yields and detonation heights. Yield can vary a lot and is difficult to estimate because yields are often secret and can be changed in similar sizes of missiles because the nuclear material is not a heavy part of the missile. Historically, ICBMs in the Russian Arsenal include a range from ~40 kilotons to ~6 megatons. The largest bomb ever tested was Tsar Bomba, which had a yield of about 50 megatons.

States generally keep modern yields secret, but common yields of ICBMs in the US and Russian arsenal would almost certainly include warheads with yields in the 100-500 kiloton range and might include weapons of 1 to 6 megatons. I’m basing this guess off of Wikipedia’s list of nuclear weapons.

Nuclear War

Estimates vary, but an EA Forum survey put the annual probability of US-Russia nuclear war at 0.24%. Living in the US, Russia, Canada, and Northern Europe this is the most concerning nuclear threat. 9 countries possess nuclear weapons.

Nuclear Winter

Nuclear winter is a controversial risk. During the cold war the security community and the scientific community disagreed about how bad a nuclear winter would be or even if it was possible. The cooling effect depends on a lot of things. How much smoke is created, how much of it is black carbon, how high is that lofted in the atmosphere, what is the weather, were there firestorms, what materials were burned, etc. Looking through the scientific literature, there’s a lot of uncertainty, but in an all out nuclear war between Russia and the US, a nuclear winter lasting months to years seems plausible. If there were a nuclear war between, say, India/​Pakistan (about 100 nukes each) there would likely be global climate effects, but probably not nuclear winter. If you were prepping for nuclear winter you’d want months of stored food and water in a place away from potential targets. In the case of nuclear winter, you’d likely want to evacuate to somewhere in the southern hemisphere.


The probability of large scale damage from EMP could be higher than other kinds of damage from nuclear weapons because it takes fewer weapons to affect a large area. A single nuclear weapon detonated high enough in the atmosphere could affect an area about the size of the US. What we know about EMP comes from tests done by the US and Russia during the cold war. The US test took out all known satellites at the time and the russian test irreparably damaged several miles of power lines. The major concern from EMP is damaging the electrical grid. The US electric grid depends on Large Power Transformers. If the large power transformers were damaged it could take a long time to replace them. They depend on a lot of custom parts and rare materials. Large Power transformer production takes 1 to 2 years. Perhaps that would be sped up in an emergency or it could take longer if critical resources or supply chains are damaged. I could also imagine transitioning to more localized grids in that situation, but that would still result in unreliable electricity for long amounts of time.

Nuclear Power Plant Meltdown

Nuclear power plants could melt down or be the target of terrorist or state action. The radiation from a power plant meltdown is much worse than from a nuclear bomb because a nuclear bomb contains far less radioactive material. If there is a meltdown in your area you should evacuate or shelter in place depending on what emergency authorities say, what level of radiation is currently in your area, and how adequate your shelter is. The WHO estimates 4,000 direct deaths from the Chernobyl Disaster, but that number is fairly controversial. Contaminated food sources could also be concerning. Contamination occurred from the Fukushima Daiichi disaster, but this article suggests the risk from that contamination was fairly low.


Here’s a handy visual on radiation dosage. Risk of harm from radiation depends on both the dose and the dose rate. 1,000 microsieverts over an hour is much more damaging than 1,000 microsieverts over a year.

  • Some of the relevant numbers from the infographic. . .

MicrosievertsOver what time period?Effects
100,0001 YearLowest annual dose where we have solid studies on increased cancer risk
500,0001 DayDecrease in blood cell counts, returning to normal after a few days if exposure stops.
1,000,000HoursTemporary radiation sickness, low blood cell count, not fatal.
4,000,000HoursBleeding, hair loss, possible death within 6 weeks, death more likely if untreated.
6,000,000HoursUsually fatal within 2-4 weeks if untreated
10,000,000HoursFatal Dose, Death within 2 weeks

Prepare Before

Sign up for Emergency Alerts

The government may send out emergency alerts via text. In order to receive these, the alerts will need to be turned on in your phone. In theory these alerts should only be about disasters in your geographic region or imminent threats to your safety. Amber alerts are different and you can choose to turn those on or off separately.

  • Instructions to turn on alerts for iPhone and android

  • The alerts are tied geographically to your phone. So you should get an alert even if you are not at your home zip code.

    • These Emergency alerts don’t work on all older phones.

    • There is a setting in your phone that needs to be turned on in order to receive the alerts. It is the emergency and public safety alerts. It was unclear the difference between “Emergency Alerts” and “Public Safety Alerts”. Probably best to leave both on.

  • Consider subscribing to local emergency alert systems.

    • In the Bay Area, the AC Alert system exists. Subscribe to receive text messages and/​or emails with local emergency alert information.

Sign up for Ben Landau Taylor’s Evacuation Email

  • Ben Landau Taylor wrote up a blog post on evacuating if a nuclear war seems imminent. You can sign up to receive an email if he decides to evacuate here.

Consider Evacuation Triggers

  • Your evacuation trigger could just be receiving the email from Ben. You might also consider . . .

    • Threats from leaders of nuclear countries

    • Non-nuclear war between nuclear powers

    • Coup or collapse of the government of a nuclear power

Plan an Evacuation Route

For leaving before a nuclear event

  • If you’re leaving before a nuclear war, places in the southern hemisphere are better. Most nuclear powers and their potential targets are in the northern hemisphere and nuclear winter models show most effects in the northern hemisphere.

  • You probably already know that New Zealand and Australia are good bets. Here’s a list of countries that are mostly food exporters and have typically been easy to get visas to if you live in the US or EU.

  • If you have to stay in the US, get away from major population centers and military bases.

For Missiles Inbound

  • You would shelter in place or go to the nearest available shelter. See the Survive During section for detailed information on sheltering.

  • Plan ahead on where you could run to whether it’s your home or a group shelter. Generally you want to be behind thick/​dense material. Being able to seal off your room from the outside world is valuable as is good air filtration.

    • Since I live in Berkeley I would run to the Bart tunnel if I knew a nuclear missile was incoming. It’s just a couple minutes from where I live, and it’s underground with cement walls for shielding.

Store Nuclear Specific Items

  • Potassium iodide thyroid tablets—Avoid radiation buildup in your thyroid

  • Geiger Counter—Test radiation levels in your shelter and outside to aid decision making

  • Emergency Radio—Stay up to date on emergency recommendations during the disaster

    • Shield the electronics—The effects of EMP on personal electronics are not well studied. To ensure your electronics are protected, wrap them in one layer of plastic (could be a ziploc) and then 5 layers of aluminium foil.

  • Plastic Sheeting and Tape—Seal off your shelter for the first few hours of fallout.

  • N95 or P100 - An N95 or P100 can reduce the amount of radioactive particulate you breathe in if it’s in the air.

  • You should already be storing some food and water for a variety of disasters.

Prepare for a world without electricity

In addition to the things in Preparing for Power Outages in Disasters, you’d need to shield your personal electronics to be sure they’d survive an EMP. You can do this cheaply by wrapping electronics in plastic wrap(or a ziploc), then 5 layers of tin foil.

  • For a HEMP(High-altitude Electro-Magnetic Pulse) the electrical grid could be out for months, so having alternate electricity would be more important than other disasters. Solar panels or gas storage might be options if you’re willing to put in a lot of effort for the tail risk here.

Store Water

As with other disasters you’ll want to store water for sheltering and evacuating. In a nuclear emergency, avoid tap water as it could have picked up radioactive particulate.

Water Preparedness for Disasters

Store Food

As with other disasters you’ll want to store food for sheltering and evacuating.

Food Preparedness for Disasters

Make a Bugout Bag

You’ll want to be able to evacuate elsewhere. In a nuclear emergency be sure to bring your geiger counter and masks as well (masks can help filter out radioactive particulate).

Bugout Bags for Disasters

Survive During

What if a missile is inbound?

Take Shelter

You’ll need a place as close by as possible with as many layers of material between you and the outside world as possible. If you’re in the blast radius you’re probably just dead, so this is for if you’re outside the blast radius and preparing to avoid radiation.

  • If you’re in a home, a basement would probably be your best bet. Unless there were more adequate shelter within a couple minutes run of your home. If you were in a basement you’d also want to cover up any exits or floor level windows with as much material as you could (boards, books, etc.).

  • Once the radiation has died down(FEMA recommends waiting 24 hours) you should evacuate. Evacuate in a direction not downwind if possible. On the California Coast wind often travels from west to east, so it would make sense to evacuate north or south.

  • You may want to use a public shelter if it’s close enough. To find the nearest open shelter in your area, text SHELTER + your ZIP code to 43362 (4FEMA).


If you think you’ve been through an area with radioactive particles on your way to shelter, you should decontaminate.

  1. Perform decontamination in a room that you will not shelter in

  2. Remove all clothing

  3. Wash yourself with tepid/​lukewarm water (cold water might trap radioactive material in your pores, hot water increases absorption rate through increased skin blood flow).

  4. Repeat step 3

  5. Ensure contaminated clothing and water does not go into rooms you’ll be staying in. If you have extra cloths/​blankets, cover the contaminated material.

Seal off your shelter

  • Close all windows and doors. Turn off all fans, air conditioners, and anything else bringing air into the house. Seal off the room with plastic sheeting(anything you can do to seal off airflow; garbage bags, plywood, etc.) and duct tape. Remove the seal after a few hours. You don’t want to suffocate, you just want to keep the radioactive particulate from getting in, which will settle out of the air over time.

    • You can also wear your N95s/​P100s.

      • Be sure to run a mask fit test.

Take Iodine Tablets

FDA instructions on taking iodine tablets

Directions for Making the Potassium Iodide (“KI”) Solution:

Step 1. Soften the KI tablet:

  • Put one 130 mg KI tablet into a small bowl. Add four teaspoons of water. Soak the tablet for one minute.

Step 2. Crush the softened KI tablet:

  • Use the back of the teaspoon to crush the tablet in the water. At the end of this step, there should not be any large pieces of KI. This makes the KI and water mixture.

Step 3. Add a drink to the KI and water mixture:

  • Mix four teaspoons of juice(you can use water, but juice will make it taste better) mixture made in Step 2. Now you have the final KI solution.

Step 4. Give the right amount of the final KI solution, using the chart below.

How Much of the Final Potassium Iodide (“KI”) Solution to Give Each Day


Once Daily Dose of KI Solution

19 years and older

8 teaspoons

13 to 18 years (150 pounds or more)

8 teaspoons

13 to 18 years (149 pounds or less)

4 teaspoons

4 to 12 years

4 teaspoons

Older than 1 month to 3 years

2 teaspoons

Birth to 1 month

1 teaspoon

What do I do after the explosion?

Some of this will be redundant with what to do if a missile is inbound. Feel free to ignore the advice you’ve already taken.

Take Shelter

Something you can get to as quickly as possible that will be as safe as possible. To find the nearest open shelter in your area, text SHELTER + your ZIP code to 43362 (4FEMA), example: shelter 12345.

  • Use the visual from the earlier take sheltersection to choose a shelter location.

Take Iodine Tablets

Evacuate the area if safe

What Direction should I evacuate?

  • Evacuate Perpendicular to downwind of the blast


How long should I wait inside?

  • In reality this depends on where you are relative to the bomb went off, how big the bomb was, whether it was air or ground burst, and which way the wind is blowing. You probably won’t know all of those things so here are some heuristics.

    • FEMA and suggest 24 hours. This is when the radiation will be at it’s worst. If you suspect you are in a zone of radiation or downwind you should stay inside for at least 24 hours if you have reasonable shelter.

    • Several prepper blogs suggest 48 or 72 hours.

    • From “A nuclear explosion produces a complex mix of more than 300 different isotopes of dozens of elements, with half-lifes from fractions of a second to millions of years. The total radioactivity of the fission products is extremely large at first, but it falls off at a fairly rapid rate as a result of radioactive decay. Seven hours after a nuclear explosion, residual radioactivity will have decreased to about 10 percent of its amount at 1 hour, and after another 48 hours it will have decreased to 1 percent. (The rule of thumb is that for every sevenfold increase in time after the explosion, the radiation dose rate decreases by a factor of 10.)”

  • Using radiation measuring devices:

If you have a geiger counter or dosimeter, you might use that to determine when to leave your shelter to evacuate the area. The threshold is up to you, there’s not official recommendations about what geiger reading you should evacuate at. Finan would consider the current radioactivity inside the shelter, the radioactivity outside the shelter, and how long to get to a safer place if evacuating.

  • Example:

If the radiation inside was 400,000 microsieverts and outside it was 1,000,000 microsieverts. Finan would evacuate immediately if he thought it was 2 hours to safety, but not if he thought it was 10 hours.

How will I evacuate if cars aren’t working?

You may think cars would be shut down making it difficult to evacuate, but mostly cars are fine after EMP, especially if they’re turned off.

  • If your car is not working, consider the time it would take to walk in your decision making.

Seek Medical Attention

If you’ve been near a nuclear explosion or accident you could have radiation sickness. Seek medical attention if available.

What if a nuclear power plant melts down?

In the case of a nuclear power plant meltdown almost all of the advice above applies.

The differences . . .

  • Because a power plant meltdown doesn’t have the same kind of explosive power as a nuclear bomb, you might be able to evacuate immediately rather than sheltering in place. Evacuate immediately if . . .

    • Emergency authorities tell you to.

    • The radiation has not yet reached you (as checked by emergency authorities or geiger counter).

    • The radiation is not yet very bad outside and you expect it to get worse.

  • In all cases you want to evacuate perpendicular to downwind of the nuclear plant.

  • If you do end up sheltering in place because you were close to the power plant or did not get word of the meltdown before radioactive particulate in the air reached you, you may have to shelter in place for longer(because there is more radioactive material in a power plant than in a nuclear bomb). Listen to emergency authorities and use a geiger counter if you have one to determine if it’s safe to evacuate. If your shelter is not very good (eg. a wood framed house), consider evacuating immediately if you can get to safety relatively quickly. Refer to the sections on radiation and taking shelter to determine what seems the safest course of action.

Additional Resources