# About constant power normalization during eigenvalue calculation and depletion and photo-fission contribution to the eigenvalue **URL:** \ **Category:** User Support\ **Created:** [July 8, 2024, 10:39am UTC](https://openmc.discourse.group/t/about-constant-power-normalization-during-eigenvalue-calculation-and-depletion-and-photo-fission-contribution-to-the-eigenvalue/4535 "2024-07-08T10:39:21Z")\ **Posts on this page:** 1\ **Showing post:** 3
**Author:** ![GasperSrsen](https://avatars.discourse-cdn.com/v4/letter/g/b4bc9f/32.png) [@GasperSrsen](https://openmc.discourse.group/u/GasperSrsen)\ **Post date:** [July 22, 2024, 10:58am UTC](https://openmc.discourse.group/t/about-constant-power-normalization-during-eigenvalue-calculation-and-depletion-and-photo-fission-contribution-to-the-eigenvalue/4535/3 "2024-07-22T10:58:00Z")
After a week of poking around i have successfully gotten agreeable results between OpenMC and Serpent: 1. Easiest way was to change fission energy release in Serpent: set U235H 193.4054000, for which i read the value from OpenMC depletion chain file. NOTE: Actual power output is higher as we are disregarding any delayed power from fission product decays and any power produced by absorption reactions other than fission. For detectors i used Serpent predefined energy grid: ene egridd 4 scale238, for which the bins are defined in the Serpent manual. I converted them into an array multiplied by 1e6 (MeV to eV). In 2-D simulations Serpent gives some results normalised per unit length, so to get correct results you may need to multiply by 100. For OpenMC normalization use the tally “kappa-fission” and follow the [guide](https://docs.openmc.org/en/stable/usersguide/tallies.html#normalization-of-tally-results). Watch out for volumes if any cell or material filters are applied. 2. For the solver I used the OpenMC default cram48 method, which is called in Serpent by: set bumode 2 -48 . The problem was the integrator, only CE, CE/LI and LE/QI are supported by both programs. CE is quite unprecise and for the other two I am not sure in the same implementation. Nonetheless LE/QI integrator in OpenMC and for Serpent: set pcc 5 1 2 2 2 yielded results agreeing within 60 pcm at worst. NOTE: calculation time is quite a bit longer in OpenMC than in Serpent (maybe parallelization). 3. Make sure that the libraries used were compiled from the same ENDF file and if run on a cluster that slurm files have the correct PATH for the library. Neutronics simulation is the default value in settings, photons are desregarded. Note to any developers: Can we get a local energy deposition addition for Q\_capture like in Serpent: set edepmode 1 [some extra heating]? --- _[View the full topic](https://openmc.discourse.group/t/about-constant-power-normalization-during-eigenvalue-calculation-and-depletion-and-photo-fission-contribution-to-the-eigenvalue/4535)._