I am working on using the depletion module for a problem and trying to test its capabilities against other activation codes such as ALARA or FISPACT-II. I just want to make sure that my understanding is correct. As I’ve read in the theory and methodology section 9.3.2 the transport solver does not allow energy-dependent capture branching ratios. Although it does say that if a spectrum averaged capture branching ratio is calculated it is possible. I’d like to understand what this really means. I am using the transport coupled solver, which should take into account the neutron energy during interaction, correct? What exactly am I missing out on by not having a spectrum-averaged capture branching ratio specific to a fusion environment? If I were to export a decay chain defining all reactions, nuclides, using ENDF-VIII.0 will I be missing interactions because my source term is higher energy than a fission reactor?
Hello, this repo might be helpful: Jonathan Shimwell put a lot of effort into making it useful and pretty. Basically by not taking into account the fusion-spectrum-adjusted branching ratios, you might be missing out on some isotopes generated from some threshold reactions.
I’d like to understand what this really means.
During depletion the spectrum in material cell of interest may shift in such a way that capture reactions on nuclides shift the fraction of how much goes into a metastable state and how much into a ground state of the daughter. This may be interesting when one of the two states has a much higher half life and therefore may be relevant for some waste or operational metric. In the depletion chain file of OpenMC there are constant branching ratios for capture reactions, which really just represent one spectrum (e.g. 1 burn-up state). In FISPACT-II you can use the PRINTLIB 4 to print out the collapsed cross-sections for the input spectrum and for the defined nuclear library.
Here is a random example for Sn126(n,g) to Sn127 or Sn127m, where the plot shows the change of the branching ratio along burn-up in a thermal reactor pin cell (using OpenMC spectra and printlib4 from FISPACT-II). At the end a little bit more goes into the ground state Sn127, anyway both Sn127m and Sn127 end up to be Sb127 after some hours (changing branching ratio not relevant).
