Get the Keff value when run in fixed source mode in depletion calculation

User Support
1

Hi all,
when run in fixed source mode in depletion calculation, the openmc.deplete module can not
run automatically to calculate keff value, do we need to modify the openmc.deplete module, or is there any way to deal with this problem?

2

Hi @zhaozelong. The ability to perform depletion calculations with a fixed source was just added to the code about a month ago, so it doesn’t appear in the most recent release but will be included in our next release. You can find the details of the new capability here. In summary, you need to:

  • Specify openmc.deplete.Operator(..., normalization_mode="source-rate") when creating the operator
  • Set the absolute source rate in neutrons/sec for each timestep using the source_rates argument of the integrator classes, e.g. openmc.deplete.PredictorIntegrator(op, timesteps, source_rates=[...])

To be clear, in a fixed source calculation, k-effective is not calculated at all or used for depletion purposes. The rate of change of nuclide densities is determined by the reaction rates corresponding to the source rate (neutrons/sec) that you as the user specify.