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Abstract

Method for concentrating nitrogen isotope to obtain a final product nitrogen, in which the stable nitrogen isotope, ¹⁵N, is concentrated, by low-temperature distillation of raw material nitrogen containing trace amounts of oxygen and argon using a plurality of distillation columns in a cascade arrangement. An argon-oxygen mixture is discharged from the bottom of the final column and ¹⁵N-concentrated nitrogen is extracted from a lower intermediate point of the final column. The flow rate of the argon-oxygen mixture discharged from the bottom of the final column is controlled based on the reading of a thermometer installed below the point where the final product ¹⁵N-concentrated nitrogen is extracted, thereby providing a stable nitrogen product.

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First Claim