Chemical composition of 15 magnetic spherules collected from deep sea sediment was determined by instrumental neutron activation
analysis (INAA) under two different irradiation conditions using the Kyoto University Reactor (KUR). Based on their chemical
composition, nine spherules were judged to be of extraterrestrial origin. The differences in the chemical composition of the
nine spherules are discussed in terms of condensation temperatures for the elements. Comparing the detection limits derived
from INAA under two different irradiation conditions, the sensitivity for INAA using KUR is discussed.