Nuclides that were not present at the moment of shutdown appeared after a period of cooling

The activities of the induced nuclides ( \text{resnuclei} ) at different decay times were processed using the command ( \text{usrsuwev} ). The results are attached. Nuclides that were not present at the moment of shutdown appeared after a period of cooling. For example, in the detector source 3, nuclides such as H-3, Fe-59, and Zn-65 appeared after 1 hour of decay, which were not present at the moment of shutdown. What could be the reason for this?
acc_80_ir3600h_coolling_1min_30min_1h_4h_res.lis (112.4 KB)
acc_80_ir3600h_coolling_1min_30min_1h_4h_sum.lis (840.0 KB)
acc_80_ir3600h_coolling_1min_30min_1h_4h_tot.lis (5.7 KB)

Hello,

Without an input file, I’m not sure exactly what simulation you performed.
Considering the isotopes you mentioned, the typical reaction is a neutron capture; therefore, I would expect a peak at the end of the irradiation time, rather than after 1 hour of cooling.

If you share the input file with me, I can take a look as well.
Have a nice day.

Cheers,
Daniele