Energy and the EnvironmentFall2012
Energy and the Environment Fall 2012
Flashbacks of Last LectureNuclearreactors-Boilingwaterreactors-Pressurizedwaterreactors-Gas-cooledreactors-Breederreactors
Flashbacks of Last Lecture • Nuclear reactors – Boiling water reactors – Pressurized water reactors – Gas-cooled reactors – Breeder reactors
Nuclear-Fueled Power Plants:Nuclear Fuel Cycle. The nuclear fuel cycle starts from mining uranium (orthorium)ore（铀(钰)矿开采),throughextraction of theuseful uranium concentrate(铀提取),gasification to UF6(UF气化),enrichmentof235U(铀浓缩)，conversiontometallicuraniumoroxideofuranium（铀转化)，fuelrodfabrication（燃料棒组装），loadingofareactor（反应堆燃料加载），retrievalofspentfuel（乏燃料回收)，reprocessingofspentfuel（乏燃料处理),andfinallyfuelwastedisposal(燃料废物处置）
Nuclear-Fueled Power Plants: Nuclear Fuel Cycle • The nuclear fuel cycle starts from mining uranium (or thorium) ore (铀(钍)矿开采), through extraction of the useful uranium concentrate (铀提取), gasification to UF6 (UF6气化), enrichment of 235U (铀浓缩), conversion to metallic uranium or oxide of uranium (铀转化), fuel rod fabrication (燃料棒组装) , loading of a reactor (反应堆燃 料加载) , retrieval of spent fuel (乏燃料回收), reprocessing of spent fuel (乏燃料处理), and finally fuel waste disposal ( 燃料废物处置)
Nuclear-Fueled Power Plants:Nuclear Fuel Cycle. Mining and refiningRich ores maycontain upto2% uranium, medium-grade ores 0.5-1%,and low-gradelessthan0.5%LargedepositsarefoundinAustralia,Kazakhstan,Canada,SouthAfrica, Namibia, Brazil, and RussiaBecauseuraniumdepositsarealwaysassociatedwithdecayproducts of uranium, these ores can be radioactive, and workers'protection must start at the mining phase
Nuclear-Fueled Power Plants: Nuclear Fuel Cycle • Mining and refining – Rich ores may contain up to 2% uranium, medium-grade ores 0.5– 1%, and low-grade less than 0.5% – Large deposits are found in Australia, Kazakhstan, Canada, South Africa, Namibia, Brazil, and Russia – Because uranium deposits are always associated with decay products of uranium, these ores can be radioactive, and workers’ protection must start at the mining phase
Nuclear-Fueled Power Plants:Nuclear Fuel Cycle.Mining and refining- The ore is crushed and leached (浸出)with sulfuric acid, throughwhichuranium,togetherwithsomeothermetals,dissolvesUraniumoxidewiththeapproximatecompositionU,O.,calledyellowcake(黄饼),isprecipitated(沉淀),dried,andpacked into2oo-literdrumsforshipment,fromwhichtheradiationisnegligible The solids remaining after leaching with acid may containradioactiveisotopesofradium(镭),bismuth(铋),andleadandthesesolidsarepumpedasaslurrytothetailingsheap(尾矿堆)alsocalledtailingsdam-Thetailingsmustbecoveredwithclay(粘土)orotherimpenetrablematerialtoprotecthumans andanimalsfrom radiationexposure
Nuclear-Fueled Power Plants: Nuclear Fuel Cycle • Mining and refining – The ore is crushed and leached (浸出) with sulfuric acid, through which uranium, together with some other metals, dissolves – Uranium oxide with the approximate composition U3O8 , called yellow cake (黄饼), is precipitated (沉淀), dried, and packed into 200-liter drums for shipment, from which the radiation is negligible – The solids remaining after leaching with acid may contain radioactive isotopes of radium (镭), bismuth (铋), and lead and these solids are pumped as a slurry to the tailings heap (尾矿堆), also called tailings dam – The tailings must be covered with clay (粘土) or other impenetrable material to protect humans and animals from radiation exposure