How to Prepare for a Nuclear Attack: A Practical Preparedness Guide

The New START treaty between the United States and Russia expired in February 2026, ending the last formal arms-control agreement between the two nations with the largest nuclear arsenals on earth. The Bulletin of the Atomic Scientists has noted that the architecture of nuclear restraint built over half a century has largely unraveled. Meanwhile, the World Health Organization has begun preparing for nuclear-related scenarios tied to the ongoing Iran crisis.

This is not fearmongering. It is an assessment of conditions. And conditions have changed enough that a civilian nuclear preparedness plan is no longer fringe thinking. It is baseline risk management.

This guide covers what you actually need to know: the physics of a detonation, how to shelter, what to stock, and when to move.

Understanding the Threat

A nuclear detonation produces three immediate effects: the blast wave, thermal radiation, and ionizing radiation. A fourth effect, radioactive fallout, follows within minutes to hours depending on wind and yield.

For a typical 300-kiloton warhead (a common estimate for modern strategic weapons), the Department of Homeland Security Planning Guidance for Response to a Nuclear Detonation outlines these survival zones:

• 0 to 1.5 miles from ground zero: survival rate under 5 percent. Infrastructure is destroyed. There is no meaningful preparation for this zone.
• 1.5 to 3 miles: survival requires immediate shelter. Blast damage is severe, but reinforced structures remain standing. Survival rates range from 10 to 50 percent depending on shelter quality.
• 3 to 9 miles: primary threats are broken glass, flash burns, and fallout. Proper shelter pushes survival rates to 50 to 95 percent.
• Beyond 9 miles: blast effects are minimal. Fallout is the primary risk, and it is entirely manageable with preparation.

The takeaway: if you are outside the immediate blast radius, your survival depends almost entirely on what you do in the first 10 to 30 minutes after detonation.

The 7:10 Rule of Fallout Decay

Radioactive fallout is dangerous, but it decays on a predictable schedule. The DHS teaches the 7:10 Rule of Thumb: for every 7-fold increase in time after detonation, radiation intensity drops by a factor of 10.

In practice, this means:

• At 1 hour after detonation: radiation is at its peak level (call it 100 percent)
• At 7 hours: radiation drops to 10 percent of the 1-hour level
• At 49 hours (roughly 2 days): radiation drops to 1 percent
• At 2 weeks: radiation drops to 0.1 percent

If the dose rate is 500 roentgens per hour at the 1-hour mark, it falls to 50 R/hr by hour 7, 5 R/hr by hour 49, and 0.5 R/hr at two weeks. The first 24 to 48 hours are the most dangerous window. If you can shelter effectively through that period, you have eliminated the majority of the fallout risk.

Choosing and Preparing Shelter

According to Ready.gov (the federal government's official preparedness resource), the ideal shelter after a nuclear event is the basement of a large, sturdy building, or the interior rooms of a multi-story concrete or brick structure. The goal is to put as much dense material as possible between you and the outside air.

Shielding effectiveness is measured in halving thicknesses, the amount of a given material needed to cut gamma radiation exposure by 50 percent. Ten halving thicknesses reduces exposure by roughly 1,000 times. Here are the numbers:

• Packed earth: 3.6 inches per halving thickness (36 inches for 1,000x reduction)
• Concrete: 2.4 inches per halving thickness (24 inches for 1,000x reduction)
• Steel: 0.7 inches per halving thickness (7 inches for 1,000x reduction)
• Wood: 8.8 inches per halving thickness (88 inches for 1,000x reduction)

A standard basement with 24 or more inches of earth and concrete overhead provides significant protection. If you are sheltering above ground, move to the center of the building, away from windows and exterior walls. Underground parking garages and subway stations are also effective.

Shelter Preparation Steps

1. Identify your two best shelter options within 10 minutes of your home and workplace. Time them. If you cannot reach adequate shelter in 10 minutes, your plan needs revision.
2. Pre-position water and basic supplies in your shelter location if possible.
3. Seal windows and doors with plastic sheeting and duct tape. This is a secondary measure, but it reduces the infiltration of fallout particles into your air supply.
4. Plan for sanitation. A 5-gallon bucket with heavy plastic bags and kitty litter serves as an emergency toilet. You will be in shelter for a minimum of 24 hours, potentially longer.

The Nuclear Supply Kit

Your nuclear-specific supplies sit on top of a standard emergency kit. FEMA recommends a minimum 72-hour supply of food and water for any disaster. For nuclear preparedness, extend that to 14 days, since sheltering may last that long.

Water

• One gallon per person per day for drinking and basic sanitation. That is 14 gallons per person for a two-week shelter period.
• Sealed containers only. Any water exposed to fallout must be treated as contaminated.
• Water purification tablets or a gravity-fed filter as backup.

Food

• Canned goods, freeze-dried meals, energy bars, and peanut butter. Nothing that requires cooking with open flame indoors (carbon monoxide risk).
• Manual can opener. This gets overlooked constantly.
• 2,000 calories per adult per day minimum under stress conditions.

Radiation-Specific Items

• NOAA weather radio with battery and hand-crank backup. The American Red Cross confirms that battery and hand-crank radios will function after a detonation, while cell, internet, and broadcast TV may not.
• Potassium iodide (KI) tablets. The CDC states that taking KI within 1 to 2 hours of exposure to radioactive iodine (I-131) blocks more than 90 percent of thyroid uptake. FDA-recommended dosages are 130 mg for adults, 65 mg for children 3 to 18, and 32 mg for infants. KI protects only the thyroid and only against radioactive iodine. It is not a general radiation cure. Adults over 40 should only take KI when authorities specifically recommend it.
• N95 or P100 respirator masks. These filter fallout particles from breathable air. They do not block gamma radiation, but they prevent inhalation and ingestion of radioactive dust.
• Plastic sheeting (6 mil thickness) and duct tape for sealing rooms.
• Change of clothes in sealed plastic bags. If you are exposed to fallout, removing and bagging your outer clothing eliminates roughly 90 percent of external contamination, according to Ready.gov.
• Dosimeter or personal radiation detector, if available. These range from $30 pocket cards to $200 electronic monitors.

Information and Reference

Access to nuclear preparedness reference material matters when communications are down. Government publications like FM 3-11 (the U.S. Army field manual on CBRN operations) and FEMA's Nuclear Attack Planning Base contain shelter calculations, decontamination procedures, and triage protocols that are difficult to reconstruct from memory under stress. The Deadnet USB drive includes 19 military and government source documents, including references that cover CBRN response procedures, along with a local AI that can help you work through specific scenarios without requiring an internet connection.

Potassium Iodide: What Most Guides Get Wrong

KI is widely recommended, but the details matter. The CDC specifically notes:

• KI protects only the thyroid gland, and only from radioactive iodine (I-131). It does nothing against other radioactive isotopes like cesium-137 or strontium-90.
• A single dose lasts 24 hours. Continued exposure may require repeated dosing, but only under the direction of health authorities.
• KI is most effective for infants, children, adolescents, pregnant and breastfeeding women, and adults under 40. Thyroid cancer risk from I-131 exposure decreases significantly with age.
• Do not take KI preemptively. It should be taken only when public health officials direct it or when you have confirmed knowledge of a release involving radioactive iodine.

Purchase KI from a reputable supplier (iOSAT and ThyroSafe are two FDA-approved brands). Check expiration dates. A bottle of 14 tablets costs between $12 and $20.

Decontamination Procedures

If you were outdoors during or after fallout, decontaminate before entering your shelter space.

1. Remove all outer clothing and shoes. Bag them in plastic and leave them outside the shelter area. Ready.gov states this step alone removes approximately 90 percent of radioactive material on your person.
2. Shower with warm water and soap if available. Do not scrub hard or use conditioner. Scrubbing opens pores and can drive particles into skin. Conditioner binds radioactive particles to hair.
3. Wash from head to toe, allowing water to run off and away from your body.
4. Put on clean clothes from sealed storage.
5. If showering is not possible, wipe exposed skin with clean wet cloths, working from the head down.

Evacuation vs. Sheltering: When to Move

The default after a nuclear event is to shelter in place. Moving through fallout is significantly more dangerous than staying in adequate shelter. However, there are situations where evacuation becomes the correct call:

• Your shelter provides poor shielding (single-story wood frame home, vehicle, or open structure). In this case, moving quickly to better shelter within 10 minutes may reduce total exposure.
• Authorities issue evacuation orders with a designated route. Follow them.
• Fire, structural collapse, or gas leaks make your current shelter uninhabitable.
• After 48 to 72 hours, when fallout levels have dropped to 1 percent or less, evacuation may be directed to move populations out of contaminated zones.

If you must move through a fallout zone, cover all exposed skin, wear a respirator or wet cloth over nose and mouth, and move as quickly as possible to minimize exposure time. The three principles of radiation protection, as stated by OSHA and reinforced in every government guide, are: minimize time of exposure, maximize distance from the source, and maximize shielding between you and the source.

Communication and Information After a Detonation

Cell towers, internet infrastructure, and broadcast stations within the affected area will likely be damaged or overwhelmed. Your primary information source will be a battery-powered or hand-crank AM/FM/NOAA radio.

The Emergency Alert System (EAS) and Wireless Emergency Alerts (WEA) are designed to push information even when commercial networks are degraded. However, the range and reliability of these systems depends on surviving infrastructure.

Plan for the possibility that you will have no outside information for 24 to 72 hours. This is where having your own reference materials becomes directly relevant. Pre-downloaded government manuals, medical references, and preparedness guides stored on a device that does not require internet or cellular service, like the Deadnet USB drive or any offline archive you build yourself, give you a fallback when broadcast information is unavailable.

Frequencies to Monitor

• NOAA Weather Radio: 162.400 to 162.550 MHz (seven channels). These stations broadcast emergency information 24/7.
• AM radio: local stations, particularly those designated as EAS Primary Entry Points. Check your state's EAS plan for specific frequencies.
• GMRS/FRS (walkie-talkie frequencies): useful for local coordination with neighbors and family if you have handheld radios.

Building a Family Nuclear Plan

A plan that exists only in your head is not a plan. Write it down. Make sure every member of your household knows:

1. The two best shelter locations near home and near work or school.
2. The rally point if family members are separated. Choose a location that is likely to survive and is known to everyone.
3. Where the emergency kit is stored.
4. How to seal a room with plastic and tape.
5. The decontamination steps.
6. That the default action is to go inside, stay inside, and stay tuned for 24 hours minimum.

FEMA's Ready.gov recommends rehearsing your shelter plan at least twice a year, the same way you would a fire drill. According to FEMA survey data, only 39 percent of American households have developed any kind of emergency plan. That number drops to single digits for nuclear-specific plans.

Your Next Step

Today, not tomorrow, identify the best shelter location within a 10-minute walk of your home. Walk to it. Time the route. Check whether the building is accessible after hours. Then do the same for your workplace. If both locations put at least 24 inches of concrete or 36 inches of packed earth between you and the outside, you have solved the single biggest variable in nuclear survival. Everything else, the supplies, the KI, the radio, builds on that foundation. Start with the shelter.