A view shows the New Safe Confinement (NSC) structure at the Chernobyl Nuclear Power Plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. The NSC, to be placed over the existing sarcophagus, will have a span of 247 meters (270 yards) and weigh 29,000 tonnes when fully assembled, according to the European Bank of Reconstruction and Development. (Photo by Gleb Garanich/Reuters)

A guard stands at Dityatki checkpoint, marking a 30 km (18-mile) zone around the Chernobyl nuclear power plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

A containment shelter for the damaged fourth reactor at the Chernobyl Nuclear Power Plant is seen from Ukraine's abandoned town of Pripyat April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

A view of the abandoned city of Pripyat is seen near Chernobyl nuclear power plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

The coat of arms of the former Soviet Union is seen on the roof of a house in the abandoned city of Pripyat near Chernobyl nuclear power plant April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

A crucifix is seen in the deserted Ukrainian town of Pripyat April 23, 2013. Ukraine will mark the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on April 26. (Photo by Gleb Garanich/Reuters)

This June 8, 2011 photo shows a Ferris wheel at a playground in the deserted town of Pripyat, Ukraine, some 3 kilometers (1.86 miles) from the Chernobyl nuclear plant. Chernobyl and Fukushima are some 5,000 miles apart but have much in common. The towns nearest to each of these stricken nuclear power stations, in Ukraine and Japan, whose disasters struck 25 years apart, already reveal eerie similarities. (Photo by Sergey Ponomarev/AP Photo)

A doll with a gas mask lies on the frame of a bed in the sleeping room of a kindergarten in the deserted town of in Pripyat, Ukraine, some 3 kilometers (1.86 miles) from the Chernobyl nuclear plant. Chernobyl and Fukushima are some 5,000 miles apart but have much in common. The towns nearest to each of these stricken nuclear power stations, in Ukraine and Japan, whose disasters struck 25 years apart, already reveal eerie similarities. (Photo by Sergey Ponomarev/AP Photo)

The remnants of beds are seen in an abandoned in a pre school in the deserted town of Pripyat on January 25, 2006 in Chernobyl, Ukraine. Prypyat and the surrounding area will not be safe for human habitation for several centuries. Scientists estimate that the most dangerous radioactive elements will take up to 900 years to decay sufficiently to render the area safe. (Photo by Daniel Berehulak/Getty Images)

A view of the abandoned city of Pripyat is seen near the Chernobyl nuclear power plant April 23, 2013. (Photo by Gleb Garanich/Reuters)

People light candles to commemorate those who died after the Chernobyl nuclear disaster, during a ceremony at the memorial to Chernobyl firefighters in Slavutich, Ukraine, on April 26, 2013. Some 50,000 Pripyat residents were evacuated after the disaster, taking only a few belongings. They never returned, and workers and their families now live in the new town of Slavutich, 37.5 miles from the plant. (Photo by Efrem Lukatsky/Associated Press)

Women hold portraits of their relatives, victims of the Chernobyl nuclear disaster, during a ceremony in Kiev April 26, 2013. Belarus, Ukraine and Russia marked the 27th anniversary of the Chernobyl disaster, the world's worst civil nuclear accident, on Friday. (Photo by Gleb Garanich/Reuters)

People hold candles at a service in Kiev commemorating the anniversary of the Chernobyl nuclear disaster, as Ukraine marks the 27th anniversary of the world's worst nuclear disaster, on April 26, 2013. (Photo by Sergei Chuzavkov/Associated Press)