Uncertainties of DS86 and prospects for residual radioactivity measurement.

Residual radioactivity data of 152Eu, 60Co and 36Cl have been accumulated and it has been revealed in the thermal neutron region that a systematic discrepancy exists between the measured data and activation calculation based on the DS86 neutrons in Hiroshima. Recently 63Ni produced in copper samples by the fast neutron reaction 63Cu(n,p)63Ni has been of interest for evaluation of fast neutrons. Reevaluation of atomic-bomb neutrons and prospects based on residual activity measurements have been discussed.