Chernobyl cover-up: Giant shield rolled over nuclear reactor remains

The world's largest moving structure has been moved to cover up the melted-down reactor which caused the Chernobyl nuclear disaster in the former Soviet Union.

In April 1986, Reactor Number Four at the Chernobyl nuclear power station went into meltdown as a result of a botched systems test which the plant's night-shift managers insisted had to take place in the middle of a shift change.

The reactor exploded as its main turbine was allowed to spool down below the critical level needed to fully power the reactor's cooling pumps. A very readable and detailed account is available on Wikipedia, with the usual health warning as to accuracy.

The resulting plume of radioactive material spread over Northern Europe, forced the immediate evacuation and abandonment of the adjoining town of Pripyat, and made areas of Ukraine uninhabitable to humans.

Effects on wildlife were initially severe, though the longer-lasting effects appear to have been overestimated.

A concrete sarcophagus was hastily built over the collapsed reactor to contain the toxic material within. According to Reuters, a 36,000-tonne “New Safe Confinement” has been constructed next to Reactor Number Four and, over the last four days, was moved on rails into position over the existing reactor structure and the crumbling concrete sarcophagus.

"Let the whole world see today what Ukraine and the world can do when they unite, how we are able to protect the world from nuclear contamination and nuclear threats," Ukrainian President Petro Poroshenko said at the completion ceremony.

A 1,000-square mile exclusion zone, mostly downwind of Chernobyl, remains closed to the public. ®