The head of Russia's nuclear regulatory agency says small amounts of weapons grade and reactor grade nuclear materials have disappeared from the country's atomic facilities.'Instances of the loss of nuclear materials have been recorded, but what the quantity is is another question,' Yuri Vishyevsky, head of Gosatomnadzor, said Thursday. 'Of those situations we can talk about in reality, they involve either grams of weapons grade or kilograms of the usual uraninum used in atomic power plants.'Most often these instances are connected with factories perparing fuel: Eleckrostal in Moskow region and Novosibirsk,' in Siberia, Vishnyevsky said.He did not give further details...