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ナトリウム純化系用大型コールド・トラップに関する調査報告書

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The most common impurity in liquid sodium systems,oxygen,forms a crystalline precipitate at temperatures above thefreezing point of sodium. This property allows purificationof liquid sodium by a cold trap,a device in which thetemperature of the liquid sodium is reduced to near itsfreezing point and the impurity crystals are removed.Nitrogen,hydrogen and carbon,and many other impuritiessuch as fission products,corrosion products and tritium arealso removed by cold trapping,at least to varying degrees.The design and operation of liquid-metal cooled reactorstypically require several different cold trap applicationsfor purification of the reactor coolant loop,the inter-mediate coolant loops,and auxiliary systems such as fuelstorage,fresh sodium,etc. For each application,differentduty cycles are imposed from time to time by maintenance,incidents,steady-state operation,and other operationalevents. Different trap designs for specific applicationsare therefore required.Cold traps in the interm