The U.N. nuclear agency says a considerable amount of highly radioactive nuclear waste from a defunct Serbian reactor, including 13 kilograms of uranium enriched at a level close to that used to make nuclear warheads, has been sent back to Russia. Reuters looks at challenges to Rio Tinto’s bid for Riversdale. According to a local radio station, Iran has started to block transit shipments of fuel to Afghanistan. President Medvedev has called Tehran’s stance on its nuclear program ‘unreasonably tough’ and urged inspections by the International Atomic Energy Agency. Meanwhile President Mahmoud Ahmadinejad is apparently soliciting support from Turkey in advance of six-party talks. Reuters reports that Gazprom is behaving in a ‘fair and open’ manner in discussions about long-term gas supply deals with the Ruhrgas unit of E.On. Up to 55% in 2010, the Chinese media have spoken of the ‘worrisome level’ of China’s dependence on crude oil imports. New information from the U.S. Energy Information Agency suggests that shale gas reserves stateside are about twice as abundant as previously thought.