Short answer. US plans cover about 10 miles (16 km) for sheltering, evacuation and potassium iodide, and about 50 miles (80 km) for food and water 1. The IAEA suggests 3 to 5 km for precautionary action and 15 to 30 km for urgent protective action 3. France plans to 20 km 4, Belgium to 20 km with extensions to 100 km 5, and Switzerland pre-distributes iodine tablets to 50 km 8.
What is an emergency planning zone?
An emergency planning zone is the area where authorities prepare protective actions in advance: warning systems, evacuation routes, sheltering advice and, in many countries, iodine tablets 13. It is not a line where danger stops. The IAEA says its suggested sizes are a judgement of the distance within which advance arrangements are reasonable, and that in the most severe emergencies protective actions might be needed beyond them 3. The IAEA also notes that zones do not stop at national borders 3.
Most systems use two layers:
- An inner zone, where people may be told to shelter, evacuate or take iodine tablets in the first hours, to limit the dose from breathing in the passing plume 13.
- An outer zone or distance, where the main concern is contaminated food, milk and drinking water over the following days and weeks 13.
How big are the zones in the United States?
The Nuclear Regulatory Commission (NRC) sets two zones around each commercial reactor 1:
- Plume exposure pathway zone: about 10 miles in radius. Plans here aim to reduce dose from breathing airborne radioactive material. Protective actions include sheltering, evacuation and potassium iodide (KI) "where appropriate" 1.
- Ingestion exposure pathway zone: about 50 miles in radius. Plans here aim to reduce dose from eating or drinking radioactive material, including bans on contaminated food and water 1.
The NRC says the size and shape of each zone vary from plant to plant with site conditions 1. The NRC supplies KI tablets to states that request them for people within the 10-mile zone, and states may recommend KI as a supplement to evacuation or sheltering 2.
What does the IAEA recommend?
The International Atomic Energy Agency's 2013 guidance for light water reactors suggests two zones and two distances. The suggested maximum radii depend on reactor thermal power 3:
| IAEA zone or distance | Purpose | Reactors ≥ 1,000 MW(th) | Reactors 100–1,000 MW(th) |
|---|---|---|---|
| Precautionary action zone (PAZ) | Public starts urgent protective actions within one hour of a General Emergency, before a release if possible | 3 to 5 km | 3 to 5 km |
| Urgent protective action planning zone (UPZ) | Public starts urgent protective actions within about one hour, without delaying the PAZ | 15 to 30 km | 15 to 30 km |
| Extended planning distance (EPD) | Instructions to reduce inadvertent ingestion; monitoring to find hotspots that may need evacuation or relocation | 100 km | 50 km |
| Ingestion and commodities planning distance (ICPD) | Instructions on local produce, milk, rainwater, animal feed and goods | 300 km | 100 km |
All figures from IAEA EPR-NPP Public Protective Actions 2013 3.
The IAEA describes these sizes as a first approximation that can be adjusted after site-specific analysis, and warns against boundaries more than a factor of two smaller or larger than the suggested range 3. It also says the real boundaries should follow local landmarks such as roads and rivers, so people can tell whether they are inside 3.
How far do the zones extend in France?
France plans protective actions within each plant's plan particulier d'intervention (PPI). The government extended the PPI around nuclear power plants from 10 km to 20 km in 2019 4. The 2019–2020 iodine campaign was the first to reach residents 10 to 20 km from the 19 French plants: about 2,200,000 people and 204,400 public buildings, including 1,800 schools, in nearly 1,100 municipalities across 33 departments 4.
Tablets in the PPI zones are made available in pharmacies, and a renewal campaign for the 0–10 km zone began on 15 September 2024 4. Outside the PPI, the State holds stocks to cover the rest of the population 4. Tablets are taken only when the prefect gives the instruction 4.
How far do the zones extend in Belgium?
Belgium's national nuclear and radiological emergency plan sets layered zones for each site 5. For the Doel and Tihange plants, and for the foreign Chooz (France) and Borssele (Netherlands) plants near the border, the plan sets 5:
- a reflex zone of 3.5 km, where warning, sheltering and the instruction to follow official broadcasts can be triggered automatically while the crisis cells are set up 5;
- emergency planning zones of 10 km for evacuation and 20 km for sheltering and iodine pre-distribution 5;
- extension zones of 20 km for evacuation and 100 km for sheltering and iodine, used if actions are needed beyond the planning zones 5.
The 100 km extension also covers the French Gravelines and Cattenom plants 5. Mol-Dessel has a 4 km evacuation zone and 20 km for sheltering and iodine; Fleurus has a 10 km zone for sheltering and iodine 5. Beyond the 20 km pre-distribution zone, the plan makes iodine available in advance across the whole country, first for minors and pregnant or breastfeeding women, with stocks in every pharmacy 5. The National Crisis Center says the tablets are free in pharmacies and must never be taken on your own initiative 6.
How far do the zones extend in Switzerland?
Swiss plans define two emergency protection zones around each nuclear plant: zone 1, with a radius of 3 to 5 km, and zone 2, with a radius of about 20 km 7. In the severe-accident scenario of the Federal Office for Civil Protection's risk dossier (February 2026), downwind doses above 10 mSv could occur even indoors out to about 50 km, beyond zone 2; the dossier puts 10 mSv at about 1.5 to 2 times the average annual dose in Switzerland 7. The scenario is one possible course of events, not a forecast 7.
Iodine tablets go further than zone 2. Households and businesses within 50 km of a Swiss plant receive tablets in advance every ten years; in 2023 about 5 million people in 779 municipalities received them 8. Outside 50 km, cantons store tablets centrally and must distribute them within twelve hours of an order 8. Tablets may be taken only on the explicit order of the authorities; the National Emergency Operations Centre (NAZ) would order intake 8.
What official agencies recommend
The agencies agree on the structure but not on the distances:
- Inner zone for evacuation and sheltering. The NRC uses about 10 miles (about 16 km) 1. The IAEA suggests 3 to 5 km for immediate action plus 15 to 30 km for urgent action 3. Belgium evacuates to 10 km and shelters to 20 km 5; France plans to 20 km 4; Switzerland uses 3 to 5 km and about 20 km 7.
- Iodine pre-distribution. The United States supplies KI on state request for the 10-mile zone 2. France and Belgium pre-distribute to 20 km 45, Belgium adds national access for children and pregnant or breastfeeding women 5, and Switzerland goes to 50 km 8.
- Food and water. The NRC plans to about 50 miles (about 80 km) 1; the IAEA suggests up to 300 km for large reactors 3.
The common rule across all of them: follow official instructions, and take iodine only when the authorities say so 2468.
Frequently asked questions
I live just outside the zone. Am I safe?
Not automatically. The IAEA says protective actions might be needed beyond its suggested sizes in the most severe emergencies 3, and the Swiss risk dossier's severe-accident scenario describes doses above 10 mSv possible out to about 50 km downwind 7. Belgium keeps extension zones out to 100 km so that sheltering and iodine can be ordered beyond its planning zones if needed 5.
Why do zones differ so much between countries?
They rest on national judgements about severe accident scenarios. The IAEA gives ranges, not single numbers, and lets each country adjust them after site-specific analysis 3. The NRC also says each US zone's size and shape vary with site conditions 1.
Should I take iodine tablets if I live in a zone?
Only when authorities tell you to. France says the prefect gives the instruction 4, Switzerland says only on the authorities' explicit order 8, and Belgium says never on your own initiative 6. The NRC describes KI as a supplement to evacuation or sheltering, not a replacement for them 2.
Where can I find my exact zone?
The IAEA says zone boundaries should follow local landmarks rather than perfect circles 3, so check with official sources. In the United States, follow your state or local government's instructions 2; in France, the PPI zones are set around each plant 4; in Belgium, the National Crisis Center lists the zones 6; in Switzerland, the FOPH page shows the 2023 distribution area 8.
Know where you stand before an alert
Whether you live inside a zone, at its edge or beyond it changes what you prepare: tablets, a shelter room, an evacuation route. Check the zones your own authorities publish. See the Phaenyx plan.
Sources
- U.S. Nuclear Regulatory Commission (NRC) — Emergency Planning Zones — https://www.nrc.gov/about-nrc/emerg-preparedness/about-emerg-preparedness/planning-zones.html (accessed 2026-10-20)
- U.S. Nuclear Regulatory Commission (NRC) — Use of Potassium Iodide — https://www.nrc.gov/about-nrc/emerg-preparedness/about-emerg-preparedness/potassium-iodide-use (accessed 2026-10-20)
- International Atomic Energy Agency (IAEA) — Actions to Protect the Public in an Emergency due to Severe Conditions at a Light Water Reactor (EPR-NPP Public Protective Actions 2013) — https://www-pub.iaea.org/MTCD/Publications/PDF/EPR-NPP_PPA_web.pdf (accessed 2026-10-20)
- Autorité de sûreté nucléaire et de radioprotection (ASNR), France — La distribution d'iode — https://reglementation-controle.asnr.fr/autres-activites/situations-d-urgence/la-distribution-d-iode (accessed 2026-10-20)
- National Crisis Center (NCCN), Belgium — Plan d'urgence nucléaire et radiologique pour le territoire belge, la mer territoriale et la zone économique exclusive — https://centredecrise.be/sites/default/files/documents/files/20240616_Plan%20d'Urgence%20Nucl%C3%A9aire.pdf (accessed 2026-10-20)
- National Crisis Center (NCCN), Belgium — Nuclear plant incident — https://crisiscenter.be/en/risks-belgium/technological-risks/nuclear-plant-incident (accessed 2026-10-20)
- Federal Office for Civil Protection (FOCP/BABS), Switzerland — KKW-Unfall — Katastrophen und Notlagen Schweiz 2025 / Gefährdungsdossier — https://www.babs.admin.ch/dam/de/sd-web/XVzFHrILlZlL/22-KKW-Unfall-GD-de.pdf (accessed 2026-10-20)
- Federal Office of Public Health (FOPH/BAG), Switzerland — Jodtabletten - eine vorsorgliche Schutzmassnahme — https://www.bag.admin.ch/de/jodtabletten-eine-vorsorgliche-schutzmassnahme (accessed 2026-10-20)
Turn this into action
A plan worked out for your household.
- Water, food and equipment counted for each person and pet
- The nuclear plants and zones around your home
- Phaenyx Safe: one tap to tell your people you are safe
Sources
- U.S. Nuclear Regulatory Commission (NRC) · Emergency Planning Zones checked 2026-10-20
- U.S. Nuclear Regulatory Commission (NRC) · Use of Potassium Iodide checked 2026-10-20
- International Atomic Energy Agency (IAEA) · Actions to Protect the Public in an Emergency due to Severe Conditions at a Light Water Reactor (EPR-NPP Public Protective Actions 2013) checked 2026-10-20
- Autorité de sûreté nucléaire et de radioprotection (ASNR), France · La distribution d'iode checked 2026-10-20
- National Crisis Center (NCCN), Belgium · Plan d'urgence nucléaire et radiologique pour le territoire belge, la mer territoriale et la zone économique exclusive checked 2026-10-20
- National Crisis Center (NCCN), Belgium · Nuclear plant incident checked 2026-10-20
- Federal Office for Civil Protection (FOCP/BABS), Switzerland · KKW-Unfall — Katastrophen und Notlagen Schweiz 2025 / Gefährdungsdossier checked 2026-10-20
- Federal Office of Public Health (FOPH/BAG), Switzerland · Jodtabletten - eine vorsorgliche Schutzmassnahme checked 2026-10-20