Residual radioactivities 60Co and 6 8 Ni are induced in iron samples exposed to
atomic-bomb neutrons through reactions 59Co(n, γ ) 60Co and 62Ni(n, γ ) 63 Ni.
60Co can be measured by the use of a low background Ge spectrometer. Since 68 Ni
emits only low- energy 0 rays, it can be measured by the low background liquid
scintillation counter. In this paper, sample preparation method to separate Co and Ni
from iron samples and an example of 68 Ni measurement are described.