Nuclear Incident Contingency in Japan
Nuclear emergency in Japan is a low-probability, high-consequence case with a written national playbook. Your part is small: know your zone, keep alerts on, and follow government instructions.1
Procedures, fees, and requirements can change. Confirm current details at the Nuclear Regulation Authority site and your prefectural nuclear-emergency plan.
Overview
After the 2011 Fukushima Daiichi accident, Japan rebuilt its nuclear-emergency system around the Nuclear Regulation Authority (原子力規制委員会, genshiryoku kisei iinkai, "Nuclear Regulation Authority"), created on September 19, 2012, with new guidelines and zones.23 Fukushima's staged evacuation reached 20 kilometers by March 12, 2011, with peak evacuees near 165,000 in May 2012.3 The reforms since have meaningfully improved safety requirements, but the residual risk is not zero, which is why the zones below exist.
The PAZ and UPZ Zones
Two zones organize every plan. The diagram compresses them into one view.
PAZ: About 5 km
The Precautionary Action Zone covers about 5 kilometers from the facility.41 Evacuation here starts preventively, before any release, keyed to Emergency Action Levels that grade the plant's condition.1 PAZ residents receive stable iodine in advance, as the next section explains.5
UPZ: About 5 to 30 km
The Urgent Protective Action Planning Zone covers outside the PAZ out to about 30 kilometers.41 Sheltering, evacuation, temporary relocation, and iodine measures here follow measured dose criteria (Operational Intervention Levels) alongside plant-condition levels.41 The two zones therefore hear different orders at different times by design.
What Residents Actually Do
Know Whether You Live Inside 30 km
This is the one peacetime check. Utilities publish the municipalities inside each plant's 30-kilometer roster, and prefectures hold the corresponding local disaster plans.1 Check on moving in; a yes means reading the prefectural pages below, and a no ends your nuclear homework.
Sign Up for Prefectural Alerts
J-Alert carries nuclear information among its instant categories, reaching residents through municipal disaster radio and phone alerts. Add the prefectural emergency app and keep phone emergency alerts enabled. Orders arrive through these channels, not through rumors or foreign media.
Shelter, Iodine, Evacuate: Only on Instruction
Specific protective actions are decided by the NRA from the accident picture, with orders issued by the national Nuclear Emergency Response Headquarters.1 Emergency classes stage the response from site-area through general emergency, with sheltering and evacuation keyed to each class.4 Sheltering means windows and doors closed with ventilation off until told otherwise. Evacuation means the assigned destination by the assigned route.
Self-evacuating early to a self-chosen destination can route you through the release path. Wait for the designated area and timing, which are set within hours under measured criteria, then move promptly.1
Stable Iodine Tablets
安定ヨウ素剤 (antei yōsozai, "stable iodine tablets") saturate the thyroid with non-radioactive iodine before or at the start of exposure, blocking uptake of radioactive iodine.6 That is all they do: one gland, one substance, no general radiation protection.6
Pre-Distribution Inside the PAZ
PAZ residents receive iodine in advance during peacetime, with physicians explaining effects, side effects, and timing, and designated pharmacies handling handover.5 Store it where the household can find it in the dark.
Urgent Distribution Inside the UPZ
UPZ local governments stockpile iodine for emergency handover, and may also pre-distribute away from stock points.5 Distribution and dosing during an emergency follow NRA determinations with headquarters or local-government instruction.5
Take Only When Told
PAZ residents take the pre-distributed tablets at the start of evacuation when instructed; UPZ dosing follows the same instruction chain.5 Ordinary iodized table salt is not a substitute and cannot block uptake.6 Never take iodine in anticipation of an event; mistimed doses add side effects without protection.6
Operating Reactors as of 2026
As of 2026, operating units include reactors at Sendai, Genkai, Ikata, Takahama, Mihama, and Tomari, with per-reactor operating status varying and documented in NRA reports (as of 2026; confirm current status with the Nuclear Regulation Authority).2 Status changes by unit and by inspection cycle, so treat any list as a starting point and verify your prefecture's current roster before drawing conclusions.
Good to Know
There is no useful DIY response beyond preparation
Monitoring radiation with a personal dosimeter, sealing a room with tape for weeks, or driving away from the assigned corridor all feel proactive and all cut against the plan. Preparation ends at zones, alerts, go-bags, and documents; the event itself belongs to official instruction.1
Iodine protects one gland against one substance
Evacuation and sheltering carry the real protection because they distance the whole body from all radioactive materials. Iodine is strictly a supplement taken on order, never a reason to delay leaving.6
Evacuation destinations are assigned, not chosen
Designated areas are named within hours under dose criteria, with temporary relocation following within about a day to a week.1 Heading to relatives outside the plan complicates registration, screening, and support, so register through the assigned channel first.