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Ukrainians hold candles commemorating the 26th anniversary of the Chernobyl nuclear disaster in Kiev, Ukraine,Thursday, April 26, 2012. Ukrainian President Viktor Yanukovych on Thursday paid tribute to the victims of the Chernobyl nuclear disaster and said his country is committed to building a new, safer shelter over the reactor as Ukrainians, Belarusians and Russians marked the 26th anniversary of the world's worst nuclear disaster. (AP Photo/Sergei Chuzavkov)

Ukrainians hold candles commemorating the 26th anniversary of the Chernobyl nuclear disaster in Kiev, Ukraine,Thursday, April 26, 2012. Ukrainian President Viktor Yanukovych on Thursday paid tribute to the victims of the Chernobyl nuclear disaster and said his country is committed to building a new, safer shelter over the reactor as Ukrainians, Belarusians and Russians marked the 26th anniversary of the world's worst nuclear disaster. (AP Photo/Sergei Chuzavkov)