Last Shipment of Nuclear Fuel From Russian Bombs Heads to U.S. PETERSBURG, Russia - The final shipment of civilian nuclear reactor fuel made from Soviet atomic bombs left port for the United States on Thursday, ending a post-Cold War program that has been a long-running boon for the American nuclear power industry. Over its 20-year course, the program, known as Megatons to Megawatts, supplied the energy for about 10 percent of all the electricity generated in the United States, far surpassing the electricity derived from solar, hydro and biofuels as well as other alternative sources. Though not well known, the program, which began in 1993, has shaped the American uranium fuel market for two decades. In that time, the Russians dismantled about 20,000 nuclear warheads, processed their high-enriched uranium cores into low-enriched fuel, and sent it to the United States. Russian nuclear fuel is now expected to drop from about 50 percent of the American market to 20 percent. Prices could rise for utilities. In a cold rain on a pier at the St. Petersburg port on Thursday, dignitaries from the United States and Russia signed placards attached to the 10 final pallets. Each pallet held four cylinders of low-enriched uranium. It took about two nuclear bombs to make each of the chunky cylinders, which look like oversize water heaters. Congratulations on the last shipment! Stay safe! Rose Gottemoeller, the acting under secretary of state for arms control and international security, wrote on one cylinder. "Happy Trails to Baltimore," Gregory Dwyer, a director of inspections of the Russian program at the Department of Energy, wrote on another canister, indicating where the shipment will end up in the United States. The entire shipment contained uranium from about 80 warheads. "Our focus globally is to minimize high-enriched uranium wherever it is found," Ms. Gottemoeller said in an interview as she watched the canisters of processed bomb cores being hoisted onto a freighter, the Atlantic Navigator. Because of the long lead time that utilities need to buy fuel, the end of this supply next month - the ship is due in Baltimore on Dec. 10 - will hardly come as a shock to the industry. The Russian supplier of the processed warhead cores, a subsidiary of the state nuclear company Rosatom, has signed commercial contracts with the United States Enrichment Corporation and about a dozen utilities. These are to supply fuel enriched from virgin uranium, rather than blended down from weapons grade metal. "This has been well planned," Ms. Gottemoeller said in an interview. The industry prepared for the winding down of deliveries. The uranium market and this program have been linked up pretty well. Though the last Russian fuel left on Thursday, it will remain in the American supply chain for many more years. The Department of Energy expects the last delivery to utilities to be in 2017. The fuel would then operate in reactors for several years, keeping the lights on in some parts of America beyond 2020. Both nuclear weapons and civilian power plants use uranium with a higher than natural percentage of the uranium 235 isotope. The difference is that weapons require enrichment to around 90 percent while most power plants use uranium enriched to between 3 and 5 percent. Under the Megatons to Megawatts program, the Russians shaved bomb cores into filings and then, through various chemical processes, blended it with the waste uranium from other enrichment processes to form low-enriched reactor fuel. This took place at two remote plants, Mayak in the Ural Mountains and Seversk in Siberia. Advocates of nuclear arms control - and utility company executives too - have said there was no reason for blending down to stop now. Both Russia and the United States have about 2,000 nuclear warheads but have committed under a new strategic arms reduction treaty signed in 2010 to reduce their arsenals to 1,550 operational warheads and 700 delivery vehicles each by 2018, freeing up more high-enriched uranium that could become electricity, in theory lowering rates for consumers. And both countries still have enormous stockpiles of bomb-grade uranium from the Cold War. The International Panel on Fissile Materials estimated that between them, the United States and Russia have about 700 tons of surplus high-enriched uranium, above what is needed for the current arsenal each country maintains. "This program represented the pinnacle of U.S.-Russian nuclear security cooperation, and its end leaves a huge vacuum that needs to be filled by a new innovative program of cooperation that puts another nail in the coffin of the Cold War," Bruce Blair, a founder of the disarmament organization Global Zero, wrote in an emailed response to questions. The United States has committed to blending down a total of 186 tons of high-enriched uranium and has so far processed about 143 tons, far less than the Russians, though the Russians are thought to still hold a larger overall stockpile. The program sprang from a suggestion by a Massachusetts Institute of Technology physicist, Thomas L. Neff - published as an Op-Ed article in The New York Times in 1991 and then circulated in the State Department - that the United States buy the Soviet Union's surplus nuclear warheads for use as nuclear fuel. It ended on Thursday when the last canister of onetime bomb cores formally changed hands. The final pallet was set on the deck of the Atlantic Navigator, and Capt. Roman N. Elokhin signed a bill of lading. Under the "free on board" terms of shipping, the United States Enrichment Corporation obtained title at the time of loading.