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Special nuclear material is a term used by the Nuclear Regulatory Commission of the United States to classify fissile materials. The NRC divides special nuclear material (SNM) into three main categories, according to the risk and potential for its direct use in a clandestine nuclear weapon or for its use in the production of nuclear material for use in a nuclear weapon. # Strategic SNM (SSNM) # SNM of moderate strategic significance # SNM of low strategic significance ==Category I== Category I is strategic special nuclear material. *Uranium-235 (contained in highly enriched uranium: >20% or more 235U), *Uranium-233, or *Plutonium-239. Category I, SSNM means SSNM in any combination in a quantity of *2 kilograms(4.4 pounds) or more of Pu-239; or *5 kilograms or more of U-235(11 pounds) (contained in uranium enriched to 20 percent or more in the U-235 isotope); or *2 kilograms(4.4 pounds) or more of U-233; or *5 kilograms(11 pounds) or more in any combination computed by the equation grams = (grams contained U-235) + 2.5 (grams U-233 + grams Pu-239). This is often referred to as a formula quantity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Special nuclear material」の詳細全文を読む スポンサード リンク
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