Qualla: Onagawa Nuclear Power Plant

Onagawa Nuclear Power Plant: Introduction

Tue, 17 Feb 2026 00:00:00 GMT

One man's stubbornness saved a nuclear power plant -- and possibly an entire region. In 1968, when engineers on the Onagawa Nuclear Power Plant construction committee debated how tall the seawall should be, most agreed that 12 meters was sufficient. Only Yanosuke Hirai, a civil engineer and power company executive, pushed for 14.8 meters, citing historical tsunami records that others dismissed. He won the argument. Hirai died in 1986, a quarter century before his decision would matter. On March 11, 2011, the most powerful earthquake ever recorded in Japan sent a wall of water surging toward the Miyagi coast. The town of Onagawa was largely destroyed. But the plant's seawall held.

Onagawa Nuclear Power Plant: The Wall That Held

Tue, 17 Feb 2026 00:00:00 GMT

The Onagawa Nuclear Power Plant sits on 432 acres of coastline in Miyagi Prefecture, straddling the border of Onagawa town and Ishinomaki city. Managed by Tohoku Electric Power Company, it was the most quickly constructed nuclear power plant in the world when its first reactor ca...

Onagawa Nuclear Power Plant: Shelter in the Shadow of Reactors

Tue, 17 Feb 2026 00:00:00 GMT

What happened next at Onagawa defied every assumption about nuclear plants and disaster. Two to three hundred residents of the town, their homes destroyed by the tsunami, evacuated to the only safe structure left standing in the vicinity: the nuclear plant's gymnasium. The reacto...

Onagawa Nuclear Power Plant: Damage, But Not Disaster

Tue, 17 Feb 2026 00:00:00 GMT

Onagawa was not entirely unscathed. A fire broke out in the turbine hall -- a building separate from the reactors -- but was quickly extinguished. On March 13, two days after the earthquake, radiation levels on site briefly spiked to 21 microsieverts per hour, triggering a mandat...

Onagawa Nuclear Power Plant: A Thirteen-Year Silence

Tue, 17 Feb 2026 00:00:00 GMT

All three reactors entered cold shutdown after the earthquake and stayed there for over a decade. In 2013, Tohoku Electric applied to restart Unit 2 under Japan's newly strengthened Nuclear Regulation Authority standards. Approval came in 2019, but additional safety upgrades and ...

Onagawa Nuclear Power Plant: Hirai's Legacy

Tue, 17 Feb 2026 00:00:00 GMT

Yanosuke Hirai never witnessed the vindication of his engineering judgment. He died 25 years before the tsunami that proved him right. Beyond the taller seawall, Hirai had also insisted the plant's water intake cooling system be designed to function even if the sea withdrew befor...