The remaining 20,000 tons came from so-called secondary uranium sources – mainly inventories held by utilities and governments, re-processed nuclear fuel, and stockpiles of depleted uranium. The supply from these sources will drop by roughly 10,000 tons at the end of 2013, when the Megatons to Megawatt Program between Russia and the United States – which recycles highly-enriched uranium from Russian nuclear warheads into low-enriched uranium for nuclear power plants – comes to an end.