In short
On March 11, 2011, a massive earthquake and tsunami struck Japan's northeast coast, disabling cooling systems at the Fukushima Daiichi Nuclear Power Plant and triggering meltdowns in three reactor cores. It became the worst nuclear accident since Chornobyl, forcing 154,000 people to evacuate and contaminating vast areas with radioactive material.
How it unfolded.
The five-minute version
What actually happened.
On 11 March 2011, a major nuclear accident started at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. The direct cause was the Tōhoku earthquake and tsunami, which resulted in electrical grid failure and damaged nearly all of the power plant's backup energy sources. The subsequent inability to sufficiently cool reactors after shutdown compromised containment and resulted in the release of radioactive contaminants into the surrounding environment. It is regarded by the United Nations Scientific Committee on the Effects of Atomic Radiation as the worst nuclear incident since the Chernobyl disaster.
Day by day.
Across 10 years, 10 pivotal moments.
Timeline
How it actually unfolded.
Tōhoku earthquake and tsunami strike
A magnitude 9.0-9.1 earthquake hits off Japan's northeast coast at 14:46 JST. The subsequent tsunami reaches 14 meters at Fukushima Daiichi, overwhelming seawalls designed for 5.7-meter waves.
External power lost, backup generators fail
Tsunami damage destroys diesel generators and electrical equipment. Plant loses ability to cool reactor cores. Emergency battery power lasts eight hours.
Reactor 1 hydrogen explosion
Pressure builds in Reactor 1 containment. Operators vent radioactive steam, hydrogen accumulates in the building, and an explosion destroys the upper structure at 15:36 JST.
Reactor 3 hydrogen explosion
Reactor 3 containment experiences similar pressure buildup and vents radioactive steam. A hydrogen explosion damages the building at 11:01 JST.
Reactor 2 containment failure
Reactor 2 suppression pool loses integrity. Pressure vessel breached. Hydrogen explosion damages the reactor building at 06:20 JST on March 15.
20-kilometer evacuation zone declared
Japanese government orders all residents within 20 kilometers of Fukushima Daiichi to evacuate. Approximately 154,000 people begin leaving the area.
INES level 7 classification assigned
Japan Nuclear and Industrial Safety Agency rates the accident Level 7 on the International Nuclear Event Scale, equaling Chornobyl. Initial rating of Level 5 is upgraded after revised damage assessments.
Cold shutdown declared
Japanese Prime Minister Naoto Kan announces that all three reactors have reached a 'cold shutdown' state where fuel temperatures stabilize below 100°C.
Reactor restart approved
Japan's Nuclear Regulation Authority approves restart of Reactor 1 at Sendai Nuclear Power Station, marking symbolic end to post-Fukushima moratorium, though Fukushima Daiichi remains offline.
Treated water release plan announced
Japanese government approves plan to release over 1 million tons of treated cooling water into the Pacific Ocean beginning 2023, sparking regional criticism.
The numbers.
7 numbers that anchor the scale.
By the numbers
The countable parts.
Reactor cores affected
0 (Units 1, 2, and 3)
Evacuation radius
0 kilometers
People evacuated
0
Estimated deaths from evacuation stress
~0
Direct earthquake magnitude
0.0-9.1 (Mw)
Tsunami wave height at plant
~0 meters
Estimated cleanup cost
$0+ billion
The chain begins -
The chain of consequence.
Impact
What followed.
The disaster killed roughly 1,600 people in evacuation-related deaths, displaced over 150,000 residents permanently, and fundamentally altered Japan's energy policy—leading to a nationwide nuclear shutdown and pivot toward renewables. It demonstrated that even advanced industrial nations with rigorous safety protocols remain vulnerable to cascading infrastructure failures when natural disasters exceed design parameters.
Captured in time.
Captured before it changed
The web as it looked, the day it happened.
Wayback Machine snapshots of the pages people actually loaded that day. Click any card to open the archive at full size.
Sources & citations.
Sources
Where this came from.
Every claim on this page traces to a public, license-clean source. We don't asterisk well.
Wikipedia
1 source- 1.Fukushima Daiichi Nuclear Disaster
en.wikipedia.org