Reactor Four Exploded Inside This Building

At 1:23:58 in the morning on April 26, 1986, Reactor Number Four at the V.I. Lenin Nuclear Power Station near the city of Pripyat blew apart from the inside.

A steam explosion tore off the thousand-ton concrete upper biological shield, a second explosion followed within seconds, and the graphite core caught fire.

Fragments of nuclear fuel landed on the roofs of the neighboring reactor building.

The night shift chief, Alexander Akimov, reported the accident to the plant director as a fire; the containment structure, in the ordinary sense of that word, no longer existed.

The reactor had been running a low-power test to see whether a coasting-down turbine could keep the coolant pumps spinning long enough for backup diesels to start.

The RBMK-1000 design was known to be unstable at low power, and the test crew, working from a rewritten and unapproved procedure, had pulled almost all of the control rods and disabled several safety systems to hold power up.

When operator Leonid Toptunov pressed the AZ-5 emergency shutdown, the boron rods entered the core behind graphite displacement tips.

In a reactor already at the edge, the graphite briefly increased reactivity instead of quenching it.

Power surged past a hundred times its rated output in about four seconds.

The fuel channels ruptured.

The first firefighters from Pripyat and Chernobyl Station 2 arrived at 1:28 a.m. and worked on the reactor block roof through the night without protective clothing, unaware that the pieces they were shoveling aside were spent nuclear fuel.

Six of them, and twenty-two plant staff, died of acute radiation syndrome by the end of July.

The city of Pripyat, fifty thousand people, was evacuated thirty-six hours after the explosion.

By the end of 1986, three hundred fifty thousand people had been resettled from a thirty-kilometer exclusion zone.

A hastily built concrete sarcophagus enclosed the reactor by November 1986.

In 2016, an international consortium slid the New Safe Confinement, a 36,000-ton steel arch, over the whole site on rails.

It is meant to hold for a hundred years.

Reactor Four sits inside it, cold, sealed, and still.

The name Chornobyl, in Ukrainian, means wormwood, the bitter herb of the Book of Revelation.

The town gave the disaster its name and gave the world the last industrial catastrophe of the twentieth century, a hundred kilometers upwind of Kyiv.