Energy-group spectra and cross section weighting

[Anne]

Hi all,

happy new year!

I have two questions concerning ORIGEN depletion calculations.

1) I get the energy-group spectra but without a time stamp so I suppose it is generated at the beginning of the calculation with no burnup? Is that correct? If not, at witch time are the spectra generated?

2) I have read about the mechanism of weithing the cross sections (COUPLE) (with flux) but I am not sure, why this has to be done. Why not just use the known cross section for each nuclide? Has this something to do with them being in equilibrium with matter surrounding them? Is the weighting perfomed per default or has it to be specified for each problem by the user?

thank you for your help in advance!

best regards,

Anne