Today in History – April 26, 1986 – The Chernobyl nuclear plant exploded in the Ukraine and parts of Belarus, Russia; it was the world’s worst civil nuclear catastrophe.

The steam explosion and fire sent a cloud of radioactive dust over much of Europe, releasing at least five percent of the radioactive core of the reactor. The accident was a result of flaws in the reactor design and inadequately trained personnel. The safety systems had actually been turned off during a testing operation and an uncontrollable power surge was allowed to occur. As the Soviet design had no external containment, there was no final barrier to contain radioactive material once the steam explosions started. These design and training flaws are attributed to lax nuclear safety standards in the former Soviet Union. Over thirty  people, mostly emergency workers and children, were killed soon after the explosion.

On May 2-4 approximately 160,000 people were evacuated from the area around the plant operator’s town of Pripyat. Eventually an additional 210,000 people resettled into less contaminated areas. The long term environmental and health effects are still being measured.  The United Nations Scientific Committee on the Effects of Atomic Radiation has  issued several reports and has conducted extensive longitudinal studies on the Chernobyl accident.  Although there is some dispute as to exactly how may long-term radiation-related deaths occurred (estimates of related deaths from cancer range from 4,000 to over 200,000) no one questions that there were catastrophic social and economic consequences, with costs in the hundreds of billions of dollars.

Only recently has the government of Ukraine indicated that it will  lift restrictions on tourism around the Chernobyl nuclear power plant. They have also announced that a 20,000-ton steel confinement  structure for the whole plant will be completed in 2013. Given Japan’s nuclear emergency after the March 11, 2011 8.9-magnitude earthquake and tsunamis, the world scrutiny of the new Chernobyl containment should be high.

Although Chernobyl is still considered the world’s worst civil nuclear catastrophe, the crisis at  Fukushima Daiichi is far from being over. Although the Japanese boiling water reactor using GE technology had an outside containment, unlike Chernobyl, the daily amount of caesium-137 released from Fukushima Daiichi is around the amount released from Chernobyl. Recent forensic modeling analyses estimate that 70 percent of the core of one reactor is damaged and that another has undergone a 33 percent meltdown. This level of damage raises many questions about what should be added to the nuclear regulatory code to improve reactor safety. The quantity of radioactive waste that must be removed raises the issue that we don’t have good solutions for long term radioactive waste disposal.

For more information, see the Engineering Pathway’s educational resources on Chernobyl and nuclear energy and safety or view our Nuclear Engineering Education and Engineeering Ethics community sites. Readers may be interested in the Alsos digital library on nuclear issues and their resources on Chernobyl as well.