Nuclear Preparedness Guide: What to Do Before, During, and After a Nuclear Event

The Bulletin of the Atomic Scientists set the 2026 Doomsday Clock at 89 seconds to midnight, the closest it has ever been. The New START treaty between the US and Russia expired in February 2026 with no replacement. The Arms Control Association reports a growing risk of nuclear proliferation, with multiple nations advancing weapons-capable programs. The WHO is actively preparing for nuclear scenarios in the Middle East.

This is not fearmongering. This is the current threat assessment from the people whose job it is to track these things. The DNI's 2026 Annual Threat Assessment identifies nuclear proliferation and the interaction of nuclear forces with AI and cyber operations as active and evolving risks.

Knowing what to do in a nuclear event takes about an afternoon of preparation. That afternoon could determine whether you and your family survive.

Understanding the Threat: What Actually Happens

A nuclear detonation produces three immediate effects: a blast wave, thermal radiation, and an electromagnetic pulse. The fourth effect, radioactive fallout, follows minutes to hours later and poses the longest-duration threat to survivors outside the immediate blast zone.

FEMA's Nuclear Detonation Response Guidance breaks the first 72 hours into three phases:

1. The first 0-60 minutes: blast, thermal effects, and initial radiation
2. The first 1-24 hours: fallout arrives and peaks
3. Hours 24-72: radiation levels drop significantly, evacuation corridors may open

For every sevenfold increase in time after detonation, radiation intensity drops by a factor of ten. That means if fallout radiation measures 1,000 roentgens per hour at 1 hour post-detonation, it drops to roughly 100 R/hr at 7 hours and 10 R/hr at 49 hours. This is called the 7/10 rule, and it is the single most useful piece of nuclear survival knowledge you can have.

Shelter: Your First and Best Defense

According to FEMA data, the most survivable action in a nuclear event is getting inside a solid structure within 10 minutes of detonation. You do not need a purpose-built bunker.

Protection Factor Ratings

Every building provides some shielding from fallout radiation. The Protection Factor (PF) tells you how much that shielding reduces your dose. A PF of 40 means you receive 1/40th the radiation compared to standing outside. Research published through the National Institute of Standards and Technology documents these approximate values:

• Open air: PF 1 (no protection)
• Wood-frame house: PF 2-3
• Basement of a wood-frame house: PF 10-20
• Concrete or brick building, upper floors: PF 10-50
• Concrete or brick building, central rooms: PF 50-200
• Underground parking garage or subway: PF 100-1,000+
• Purpose-built fallout shelter with 36 inches of packed earth: PF 1,000+

NIST data shows that 6 cm of concrete or 9 cm of packed earth cuts gamma ray exposure by 50%. Stack ten of those halving-thicknesses, roughly 36 inches of packed earth, and you have blocked over 99.9% of gamma radiation.

Identifying Shelter Now, Not Later

Survey your daily routes. Identify the nearest concrete or brick structure to your home, your workplace, and your children's school. The center rooms on the lowest floor of a multi-story concrete building provide PF values of 50 or higher, enough to keep your radiation dose survivable during the first 24 hours when fallout is most dangerous.

FEMA's guidance is direct: if you are outdoors when a detonation occurs, you have approximately 10 minutes to reach adequate shelter before fallout begins arriving. Do not try to drive. Cars provide a PF of roughly 2-3. A nearby concrete building is a better option than a distant bunker.

The Supply Kit: What You Actually Need

You are preparing to stay indoors for a minimum of 24 hours and ideally 72 hours. Pack accordingly.

Water

• 1 gallon per person per day for 3 days (the CDC minimum for emergency water storage)
• Stored in sealed containers, rotated every 6 months
• Water purification tablets or a filter as backup

Food

• 72 hours of non-perishable food that requires no cooking
• Canned goods with a manual can opener
• High-calorie bars, dried fruit, nuts, peanut butter
• Food in sealed containers is safe from fallout contamination, per CDC guidance

Radiation-Specific Items

• N95 or higher masks: reduces inhalation of radioactive particles
• Plastic sheeting and duct tape: for sealing windows and doors in your shelter room
• Change of clothes in a sealed bag: if you were outside during fallout, you will need to strip contaminated clothing
• Large garbage bags: for contaminated clothing disposal

Medical

• Standard first aid kit
• Potassium iodide (KI) tablets: FDA-approved in 130 mg and 65 mg doses
• Any prescription medications for a 7-day period
• Dosimeter or radiation detection card (available for $5-25 online)

Information and Communication

• Battery-powered or hand-crank NOAA weather radio
• Spare batteries
• Paper copies of emergency contacts and meeting points
• A loaded Deadnet USB drive gives you access to FEMA's nuclear detonation response guidance, military field manuals including FM 3-4 NBC Protection, and a local AI assistant for reference queries, all without needing internet or cell service

Potassium Iodide: What It Does and What It Does Not Do

There is widespread misunderstanding about KI pills. They are not anti-radiation medication. They do one thing: saturate your thyroid gland with stable iodine so it does not absorb radioactive iodine-131.

The CDC reports that taking KI within 1-2 hours of inhaling radioactive iodine blocks more than 90% of thyroid uptake. After 4 hours, the effectiveness drops sharply.

Dosing by Age (FDA-approved)

• Adults over 18 through 40: 130 mg
• Adolescents 12-18: 65 mg (or 130 mg if adult-sized)
• Children 3-12: 65 mg
• Children 1 month to 3 years: 32 mg
• Newborns to 1 month: 16 mg

The CDC recommends KI primarily for people under 40 and pregnant or breastfeeding women. One dose provides 24 hours of protection. Do not take more than directed. Higher doses do not increase protection and can cause thyroid damage.

KI does not protect against external gamma radiation. It does not protect against other radioactive isotopes like cesium-137 or strontium-90. It only protects one organ from one specific isotope. It is still worth having, but it is not a substitute for shelter.

Decontamination: The 20-Minute Protocol

If you were outdoors during or after fallout, decontamination is straightforward. The CDC outlines this process:

1. Remove all outer clothing. This step alone removes up to 90% of radioactive contamination on your body, according to CDC data.
2. Place contaminated clothing in a plastic bag. Seal it. Move it as far from living areas as possible.
3. Shower with soap and warm water. Scrub gently. Do not use conditioner, as it binds radioactive particles to hair.
4. If no shower is available, use wet wipes or a damp cloth on all exposed skin and hair.
5. Blow your nose, wipe eyelids and ears, and wash hands thoroughly.
6. Put on the clean clothes from your sealed bag.

Do this before entering your shelter space if possible. If you must enter first, designate an area near the entrance for decontamination and keep it separated from the main shelter area.

Communication and Information After Detonation

Cell towers, internet infrastructure, and power grids may be damaged or overloaded. FEMA's nuclear detonation communication guidance assumes that standard communication channels will be degraded or unavailable for the first 24-72 hours.

Your information sources in order of reliability:

1. NOAA Weather Radio: these transmitters are hardened and dispersed. A hand-crank radio tuned to your local NOAA frequency is the most reliable source of government emergency broadcasts.
2. AM radio: AM signals travel farther than FM and may reach you from distant, undamaged transmitters.
3. If you have a Deadnet drive, you have offline access to the full text of government nuclear response protocols, military NBC protection manuals, and a local AI you can query for specific guidance without any network connection.

Do not rely on your phone. Even if it survives the EMP component, networks will be overwhelmed. Have your emergency plan, meeting points, and contact information written on paper.

Building a Family Plan

A plan that is not practiced is a suggestion. Run through these steps with your household:

1. Designate a primary shelter location for each place family members spend time: home, work, school.
2. Identify a secondary option for each location in case the primary is inaccessible.
3. Establish two meeting points: one near your home, one outside your neighborhood.
4. Pick an out-of-area contact person. After a disaster, long-distance calls often connect when local ones cannot.
5. Store emergency contact numbers on paper in each person's wallet or bag.
6. Run a drill. Time how long it takes each family member to reach their primary shelter from their normal location. If it is over 10 minutes, find a closer option.

FEMA's Ready.gov recommends reviewing and updating your family emergency plan every 6 months.

Common Mistakes That Get People Killed

Evacuating immediately

Unless you are in the direct blast zone and still alive, evacuation in the first hours is the wrong move. Driving through fallout exposes you to far more radiation than sheltering in place. Wait for official guidance, which typically comes 24-72 hours post-detonation once radiation surveys are completed.

Sheltering in a car

A vehicle provides almost no fallout protection (PF 2-3). An interior hallway of a brick building provides 50 times more shielding.

Ignoring time

The 7/10 rule works in your favor. Every hour you stay sheltered, especially in the first 48 hours, drastically reduces your cumulative dose. Leaving shelter 2 hours early on day one can double your total exposure.

Assuming KI makes you safe

KI protects one organ from one isotope. Shelter protects your entire body from all radiation types. Prioritize shelter.

What to Do This Week

Do not file this away for later. Nuclear preparedness is a short checklist, not a lifestyle change. Here is your task list for the next 7 days:

1. Today: identify the nearest concrete or brick structure to your home that you could reach in under 10 minutes on foot. Check for basement access.
2. Day 2: buy a hand-crank NOAA radio and a pack of KI tablets. Total cost is under $40.
3. Day 3: fill and seal three 1-gallon water containers. Place 72 hours of shelf-stable food in a bag near your shelter location.
4. Day 4: assemble your decontamination kit: one sealed change of clothes per person, trash bags, wet wipes, N95 masks.
5. Day 5: write your family communication plan on a physical card. Include shelter locations, meeting points, and your out-of-area contact. Give a copy to each family member.
6. Day 6: run a timed drill with your household. Walk to your shelter location. Note obstacles and time.
7. Day 7: review what you missed and fill the gaps.

That is seven days of 15-minute tasks. At the end of the week, you are more prepared than 95% of the population. The threats outlined in the 2026 Annual Threat Assessment are not hypothetical. They are assessed risks from career intelligence professionals. Preparation is the rational response.