A combination of images, taken in 1982 and on March 31, 2011, shows before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A combination of images, taken in 1982 and on February 24, 2011, shows before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A combination of images, taken in 1982 and on April 7, 2011, shows before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A combination of images, taken in 1982 and on March 31, 2011, shows before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A combination of images, taken in 1982 and on March 31, 2011, shows before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A combination of images, taken in 1982 and on March 31, 2011 (bottom), shows the before and after view of the abandoned city of Prypiat near the Chernobyl nuclear power plant. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Vladimir Repik and Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A picture of Soviet state founder Vladimir Lenin is seen through wild flowers inside a hospital in the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union. ] 

The sarcophagus covering the damaged fourth reactor at the Chernobyl nuclear power plant is seen in the horizon from the balcony of a building in the abandoned city of Prypiat April 4, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. Engineers are still struggling to regain control of damaged reactors at the Fuskushima plant after last month's earthquake and tsunami, in the worst nuclear crisis since Chernobyl in 1986, with the government urging the operator of the plant to act faster to stop radiation spreading. REUTERS/Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A child gas mask and a doll are seen inside a kindergarten in the abandoned city of Prypiat near the Chernobyl nuclear power plant April 4, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. Engineers are still struggling to regain control of damaged reactors at the Fuskushima plant after last month's earthquake and tsunami, in the worst nuclear crisis since Chernobyl in 1986, with the government urging the operator of the plant to act faster to stop radiation spreading. REUTERS/Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

The interior of a kindergarten is seen in the abandoned city of Prypiat near the Chernobyl nuclear power plant April 4, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. Engineers are still struggling to regain control of damaged reactors at the Fuskushima plant after last month's earthquake and tsunami, in the worst nuclear crisis since Chernobyl in 1986, with the government urging the operator of the plant to act faster to stop radiation spreading. REUTERS/Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

A child's gas mask and a shoe are seen at a kindergarten in the abandoned city of Prypiat near the Chernobyl nuclear power plant, April 4, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. Engineers are still struggling to regain control of damaged reactors at the Fuskushima plant after last month?s earthquake and tsunami, in the worst nuclear crisis since Chernobyl in 1986, with the government urging the operator of the plant to act faster to stop radiation spreading.  REUTERS/Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT) 

The sarcophagus covering the damaged fourth reactor at the Chernobyl nuclear power plant is seen behind a building decorated with a graffiti in the abandoned city of Prypiat April 4, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. Engineers are still struggling to regain control of damaged reactors at the Fuskushima plant after last month's earthquake and tsunami, in the worst nuclear crisis since Chernobyl in 1986, with the government urging the operator of the plant to act faster to stop radiation spreading. REUTERS/Gleb Garanich (UKRAINE - Tags: ANNIVERSARY DISASTER ENERGY ENVIRONMENT IMAGES OF THE DAY) 

A view of the abandoned city of Prypiat, with a sarcophagus covering the damaged fourth reactor at the Chernobyl nuclear power plant in the background March 31, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY ENVIRONMENT BUSINESS) 

Rusting amusement rides are seen in the abandoned city of Prypiat, near the Chernobyl nuclear power plant March 31, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY ENVIRONMENT BUSINESS) 

A view of the abandoned city of Prypiat, with a sarcophagus covering the damaged fourth reactor at the Chernobyl nuclear power plant in the background March 31, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY ENVIRONMENT BUSINESS) 

A view of the abandoned city of Prypiat, near the Chernobyl nuclear power plant March 31, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY ENVIRONMENT BUSINESS CITYSCAPE) 

Graffiti is seen inside a building in the abandoned city of Prypiat, near the Chernobyl nuclear power plant March 31, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY BUSINESS ENVIRONMENT) 

A cross is seen in the abandoned city of Prypiat, near the Chernobyl nuclear power plant in Ukraine, February 24, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY) 

A view of an empty sports gym inside a building in the abandoned city of Prypiat, near the Chernobyl nuclear power plant in Ukraine, February 24, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY) 

The coat of arms of the Soviet Union is seen on a building in the abandoned city of Prypiat, near the Chernobyl nuclear power plant, in Ukraine February 24, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY) 

An interior view of a building shows a double bass in the abandoned city of Prypiat near the Chernobyl nuclear power plant in Ukraine February 24, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ENERGY ANNIVERSARY) 

Rusting amusement rides in the abandoned city of Prypiat near the Chernobyl nuclear power plant in Ukraine February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

A room containing Soviet placards is seen in the abandoned city of Prypiat, near the Chernobyl nuclear power plant February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

Graffiti is seen on a wall in the abandoned city of Prypiat, near the Chernobyl nuclear power plant February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY IMAGES OF THE DAY) 

A room containing disused appliances in the abandoned city of Prypiat near the Chernobyl nuclear power plant in Ukraine February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

Rusting amusement rides are seen in the abandoned city of Prypiat, near the Chernobyl nuclear power plant February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

An Orthodox cross is seen in the abandoned city of Prypiat near the Chernobyl nuclear power plant in Ukraine February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

Rusting amusement rides are seen in the abandoned city of Prypiat, near the Chernobyl nuclear power plant February 22, 2011. Belarus, Ukraine and Russia will mark the 25th anniversary of the nuclear reactor explosion in Chernobyl, the place where the world's worst civil nuclear accident took place, on April 26. REUTERS/Gleb Garanich (UKRAINE - Tags: DISASTER ANNIVERSARY) 

General view of Ukraine's ghost town of Pripyat, April 13, 2006. Ukraine prepares to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading a radioactive cloud across Europe and the Soviet Union. Picture taken April 13, 2006. REUTERS/Gleb Garanich 

A clock is seen on a wall at a swimming pool in Ukraine's ghost town of Pripyat, which was evacuated after the Chernobyl nuclear disaster, April 13, 2006. Ukraine prepares to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading a radioactive cloud across [Europe] and the Soviet Union. 

Shoes and a gas mask for children are left in a kindergarten in Ukraine's ghost town of Pripyat, April 13, 2006. Ukraine prepares to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading a radioactive cloud across Europe and the Soviet Union. Picture taken April 13, 2006. REUTERS/Gleb Garanich 

A painting of a girl decorates an empty building in the abandoned town of Pripyat in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

Newspapers from March 1986 with a picture of Soviet state founder Vladimir Lenin are seen in an empty building in the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

A view of an amusement park in the centre of the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

A view from a building in abandoned town of Pripyat, March 31, 2006, overlooking the fourth reactor of Chernobyl nuclear power plant. [Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when the reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

Medical equipment lies idle in front of a hospital in the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

Gas masks are seen in a kindergarten in the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

A piano is seen in a kindergarden in the abandoned town of Pripyat, in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.] 

Toys and gas masks are seen in a kindergarden in the abandoned town of Pripyat in the 30 km (19 miles) exclusion zone around the closed Chernobyl nuclear power plant March 31, 2006. [Around 50,000 Pripyat residents were evacuated after the disaster, taking only few belongings. Ukraine is preparing to mark the 20th anniversary of the world's worst nuclear disaster, when a reactor at the Chernobyl plant exploded, spreading radioactivity across Europe and the Soviet Union.]