Japan’s Fukushima Daichii nuclear meltdown is bad, but Ukraine’s Chernobyl was worse.  Memorial services and speeches marked the anniversary of the world’s worst nuclear disaster on Tuesday.

Ukranian President Viktor Yanukovych addressed the people Tuesday, honoring firemen, policemen and soldiers that helped during the crisis. He talked about the toll of the tragedy: “the lives and health of thousands … billions of budgetary funds … [a] decommissioned Chernobyl nuclear power plant.”

A Thomson Reuters article chronicled the events of Chernobyl:

On April 26 1986, the No. 4 reactor at the Chernobyl plant, then in the Soviet Union, exploded and caught fire after a safety test experiment went badly wrong.

The blast sent radiation billowing across Europe.

A total of 31 people died immediately but many more died of radiation-related sicknesses such as cancer, many of them in what is today Belarus.

The Chernobyl accident was rated a 7, the highest possible danger rating on the international nuclear events scale.

The consequences of Chernobyl have been studied by numerous scientists. Find out more by reading about The Chernobyl Project.