US Patent 7828939 Method for concentrating heavy nitrogen isotope

A method for concentrating effectively the heavy nitrogen isotope 15N to 50 atom % or more in which 14N15N and/or 15N2, which are molecules containing a heavy nitrogen isotope of 15N, are concentrated by distilling successively nitrogen N2 using plural distillation columns T1 to T4 each of which includes at least one condenser C1 to C4 and at least one reboiler R1 to R4 and is arranged in series, and a part of nitrogen in the distillation is drawn out to be subjected to isotope scrambling in an isotope scrambler S1, and nitrogen after the isotope scrambling is returned to the distillation to produce nitrogen N2 with a 15N concentration of 50 atom % or more.