Chernobyl disaster site enclosed by shelter to prevent radiation leaks

Ukraine plant reactor, scene of worst nuclear accident in history in 1986, covered with airtight structure after years of work

Reactor No 4 at Chernobyl, the scene of the worst nuclear accident in history, has been enclosed by a vast steel shelter designed to prevent radiation leaks from the site.

The structure covers the reactor and the unstable "sarcophagus", which was hastily built around it by Soviet authorities in the immediate aftermath of the disaster 30 years ago. The shelter is said to be the largest land-based movable object ever constructed. It took several years to build and cost more than a1.5bn (1.27bn).