01 Overview
On March 11, 2011, a magnitude 9.0 earthquake struck off the Pacific coast of Japan, generating a devastating tsunami with waves reaching 15 metres. The tsunami overwhelmed the Fukushima Daiichi Nuclear Power Plant's seawall, disabling emergency generators. Without cooling power, three reactor cores melted down over the following days.
02 Cause
The Tลhoku earthquake triggered automatic shutdown of the reactors, but the subsequent tsunami disabled all backup diesel generators. Loss of cooling caused fuel rods to overheat in Reactors 1, 2, and 3. Hydrogen gas produced by the zirconium fuel rod cladding accumulated and exploded, blowing off the upper structures of the reactor buildings.
03 Impact
Approximately 154,000 residents were evacuated. A 20km no-go zone was established. Around 2,200 deaths are attributed to the evacuation process itself. About 1 million tonnes of contaminated water was stored on-site; since 2023, treated water has been gradually released into the Pacific under IAEA monitoring.
04 Response
TEPCO faced widespread criticism for slow disclosure. Hundreds of workers remained on-site to cool the reactors despite extreme radiation. The Self-Defense Forces dropped water from helicopters on spent fuel pools. International assistance and robotic systems were deployed to assess damage.
05 Legacy
Japan shut down all 50 of its nuclear reactors for safety reviews. The event triggered nuclear policy reviews worldwide, with Germany deciding to phase out nuclear power entirely. Decommissioning is expected to take 30โ40 years and cost over $200 billion.