Nuclear Preparedness: What You Actually Need to Know and Do

In January 2026, the Bulletin of the Atomic Scientists set the Doomsday Clock to 85 seconds to midnight — the closest it has ever been. The expiration of New START, the last major arms control treaty between the U.S. and Russia, removes the final structural guardrail on nuclear arsenals. The WHO has updated its internal protocols for nuclear scenarios tied to escalation in the Middle East.

This is not a reason to panic. It is a reason to prepare. The gap between people who survive a nuclear event and people who do not comes down to a handful of decisions made in the first 10 to 60 minutes — most of which depend on knowledge you either have before the event or you don't.

The Three Words: Get Inside, Stay Inside, Stay Tuned

FEMA and Ready.gov condense nuclear response into three directives: get inside, stay inside, and stay tuned. That framing is simple because the physics are simple. Radiation intensity from fallout follows the 7-10 Rule: for every seven-fold increase in time after detonation, radiation drops by a factor of ten. One hour after a blast, radiation is at its reference level. At seven hours, it has dropped to 10%. At 49 hours (roughly two days), it is at 1%. At two weeks, one-thousandth.

The takeaway: the first 24 to 72 hours are the most dangerous window. If you can shelter effectively during that period, your odds improve dramatically.

Shelter: What Actually Protects You

Not all buildings are equal. Protection is measured by a Protection Factor (PF) — how much a structure reduces your radiation exposure compared to standing in the open.

Here are the PF ranges based on FEMA and Lawrence Livermore National Laboratory research:

• A wood-frame house: PF 2-3 (reduces exposure to roughly half — not enough)
• A standard basement: PF 10-27, depending on construction and depth
• A concrete or brick building, interior rooms: PF 10-20
• A multi-story concrete building, middle floors away from windows: PF 50-100
• A dedicated fallout shelter with 24 inches of concrete: PF 1,000 or higher

FEMA's TR-87 standard sets the minimum PF for public fallout shelters at 40. Their guidance states that a PF of 10 — reducing exposure by 90% — is sufficient to save a large number of lives in a widespread fallout event.

If you are in a wood-frame house with no basement, your best move after a detonation is to reach a better structure within 10 minutes. FEMA's nuclear detonation response guidance confirms you have roughly 10 minutes or more before fallout arrives, depending on distance from the blast. If a concrete building or underground parking structure is within a few minutes of travel, go there. If not, move to the most interior room on the lowest floor of whatever building you are in, away from windows and exterior walls.

The Supplies That Matter for the First 72 Hours

FEMA's 72-hour nuclear detonation response guidance focuses the critical window around three days. Your supply list should be built around that timeline at minimum, with two weeks as the target.

Water: One gallon per person per day. For a family of four over 14 days, that is 56 gallons. This is the heaviest and most space-consuming prep item. If you cannot store that volume, keep at least a 72-hour supply (12 gallons for four people) and a quality water filter rated for at least 0.2 microns.

Food: Shelf-stable, calorie-dense, requiring no cooking. Canned goods, freeze-dried meals, energy bars, peanut butter. Target 2,000 calories per person per day. For two weeks, that is 28,000 calories per person.

Medications: A 30-day supply of any prescription medications. Over-the-counter pain relievers, anti-diarrheal medication, and antihistamines.

Potassium iodide (KI): This is the one nuclear-specific supply item. KI blocks radioactive iodine (I-131) from being absorbed by the thyroid. The CDC reports that taking KI within one to two hours of inhaling I-131 blocks more than 90% of thyroid uptake. After four hours, effectiveness drops significantly. KI is available in 65mg and 130mg tablets. Adults under 40 take 130mg daily; children aged 3-18 take 65mg. Do not take it unless instructed by public health officials — it protects only against one type of radioactive material and does nothing against other radiation sources. Keep it in your kit, but understand its limits.

Radiation Monitoring

Without a way to measure radiation, you are guessing. Two tools change that:

A dosimeter measures your cumulative radiation exposure — how much total radiation your body has absorbed. This tells you whether you are approaching dangerous thresholds. The U.S. government's guidance considers 100 rem (1 Sv) as the threshold where acute radiation syndrome symptoms begin.

A survey meter (rate meter) measures the current radiation level in your environment. This tells you whether it is safe to move, whether your shelter is adequate, and when fallout levels have decayed enough to evacuate.

Consumer-grade Geiger counters are available for $150-400. They are not as precise as professional instruments, but they give you data where otherwise you would have none. A NukAlert keychain detector ($160-200) provides continuous passive monitoring and will alarm if radiation levels spike. Any measurement capability is better than zero.

Blast Zones and Distance

The effects of a nuclear detonation depend on yield, altitude of burst, and your distance from ground zero. For a 10-kiloton device (the size most frequently modeled in FEMA planning scenarios, roughly the yield of the Hiroshima weapon):

• Within 0.5 miles: near-total destruction, severe burns, lethal radiation dose. Survival unlikely without pre-positioned hardened shelter.
• 0.5 to 1 mile: major structural damage, third-degree burns from thermal flash, high radiation. Shelter-in-place in reinforced structures gives a chance.
• 1 to 3 miles: moderate blast damage, second-degree burns possible, fallout is the primary threat. Sheltering works here.
• 3 to 10 miles: light blast damage (broken windows, minor structural), burns unlikely, fallout is the dominant risk. Sheltering is highly effective.
• Beyond 10 miles: no direct blast or thermal effects. Fallout is the only concern, and it is manageable with proper shelter.

The majority of people within a nuclear event's impact area will be in the 1-to-10-mile zone where shelter and preparation determine outcomes. FEMA's planning guidance for a nuclear detonation estimates that adequate sheltering in that zone can reduce casualties by 50-80%.

Communication and Information

After a detonation, cell towers will likely be down or overloaded. Internet connectivity will be unreliable at best. Your information lifeline is a battery-powered or hand-crank AM/FM radio. NOAA Weather Radio (frequencies 162.400 to 162.550 MHz) carries Emergency Alert System broadcasts. The government's nuclear communication guidance emphasizes that official instructions on when to evacuate — and which direction — will come through these channels.

Keep a radio with fresh batteries in your shelter supplies. A hand-crank model eliminates the battery dependency entirely.

If communications infrastructure is destroyed in your area, you are operating on the knowledge you already have. This is where having reference material matters. The Deadnet USB drive includes FEMA's nuclear detonation response guidance and military field manuals covering CBRN (chemical, biological, radiological, nuclear) operations — the same documents first responders train from. Having those references accessible without power or internet means you can look up decontamination procedures, fallout decay timelines, and evacuation criteria when you cannot reach anyone for instructions.

Decontamination Basics

If you were outside when fallout arrived, or if you had to move between buildings:

1. Remove all outer clothing before entering your shelter. This alone removes up to 90% of radioactive particles, according to Ready.gov guidance.
2. Bag the clothing and leave it outside or in an isolated area.
3. Shower with soap and water if available. Do not use conditioner — it binds radioactive particles to hair. Wash from the top down.
4. If no shower is available, wipe exposed skin with wet cloths or uncontaminated water.
5. Blow your nose, wipe your eyelids and ears, and rinse your mouth.

The goal is removing particles. Radiation from fallout is primarily from contact with or ingestion of radioactive dust. Remove the dust, reduce the dose.

Building a 14-Day Shelter Plan

The minimum effective shelter duration is 72 hours. The recommended duration, per multiple government sources, is 14 days. Here is how to think about that:

Shelter location: Identify the best shelter option within five minutes of your home and workplace. A basement is good. An interior room in a concrete building is good. A multi-story building's middle floors are better than the ground floor (less ground-deposited fallout radiation) and better than the top floor (less skyshine).

Water storage: Store water in food-grade containers in or near your shelter location. Rotating every six months keeps it fresh.

Sanitation: A five-gallon bucket with heavy-duty trash bags and kitty litter makes a functional toilet when plumbing is out. This is not a luxury item — disease from poor sanitation in shelters has historically been a secondary killer.

Ventilation: A sealed room is not the goal. You need airflow, but it should be filtered. Wet towels over ventilation openings will catch a significant portion of particulate fallout. HEPA filters are better if you have them.

Light and power: Battery-powered or hand-crank lanterns. A small solar panel and battery bank, if you have a window or can briefly access the exterior after 48-72 hours when radiation has decayed significantly.

Entertainment and morale: Two weeks in a basement is a psychological endurance test. Books, cards, games. This is not a trivial consideration — maintaining mental function under stress directly affects decision-making when it counts.

What to Do Right Now

Nuclear preparedness is binary: you either have a plan and supplies before the event, or you don't. There is no improvising your way through the first 72 hours of a fallout scenario without pre-positioned resources.

The Deadnet offline AI assistant can help you work through scenario-specific questions — optimal shelter locations for your building type, supply calculations for your household size, fallout decay timelines — without requiring a network connection that may not exist when you need answers.

Here is the single most useful thing you can do today: identify your shelter location. Walk through your home, workplace, and daily commute route. For each, find the nearest structure with the highest protection factor — the most concrete, brick, or earth between you and the outside. Know where you would go if you had 10 minutes of warning. Write it down. Tell your household.

That one action — knowing where to shelter before you need to — is the single variable with the highest impact on survival in a nuclear fallout scenario. Everything else builds on it.