# Difference k\_eff transport and depletion version 0.14.0

**URL:** <https://openmc.discourse.group/t/difference-k-eff-transport-and-depletion-version-0-14-0/3884>\
**Category:** User Support\
**Created:** [January 31, 2024, 1:15pm UTC](https://openmc.discourse.group/t/difference-k-eff-transport-and-depletion-version-0-14-0/3884 "2024-01-31T13:15:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![daan1392](https://avatars.discourse-cdn.com/v4/letter/d/5daacb/32.png) [@daan1392](https://openmc.discourse.group/u/daan1392)\
**Post date:** [January 31, 2024, 1:15pm UTC](https://openmc.discourse.group/t/difference-k-eff-transport-and-depletion-version-0-14-0/3884/1 "2024-01-31T13:15:24Z")

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Hello everyone,

I’ve encountered an anomaly while using OpenMC version 0.14.0 installed using the Mamba package in a Conda environment. Specifically, during a depletion analysis of a sodium core, I observed a discrepancy of 100 pcm in k\_eff between running in depletion mode and transport mode. I haven’t made any changes to the model other than introducing the depletion module from OpenMC. I verified the model by transforming my model to serpent version 2.2.1 and the k\_eff of the transport part matches almost perfectly with the serpent model for depletion. These are the multiplication factors obtained:

- Transport OpenMC k\_eff: 1.00823 +/- 0.00015
- Depletion OpenMC k\_eff: 1.00726 +/- 0.00021
- Serpent depletion k\_eff: 1.00818 +/- 0.00006

Upon checking the discussion forum, it seems that a similar issue was reported in version 0.13.0-dev and version 0.13.2, as discussed [here](https://openmc.discourse.group/t/bol-keff-disagreement-transport-vs-depletion/1285) and [here](https://openmc.discourse.group/t/the-0-step-depletion-and-transport-keff-result-are-different/3074).

If anyone has insights into the potential cause of this discrepancy, I would greatly appreciate your assistance.

Kind regards,  
Daan

```auto
import openmc
import openmc.deplete

geometry = openmc.Geometry.from_xml()
settings = openmc.Settings.from_xml()
tallies = openmc.Tallies.from_xml()
model = openmc.model.Model(geometry=geometry, settings=settings, tallies=tallies)

operator = openmc.deplete.CoupledOperator(
model, '../chain_endfb71_sfr.xml')

dt = [1, 1, 4, 4, 10, 10, 10, 10, 10, 10, 10]
power = 65e6

cecm = openmc.deplete.CECMIntegrator(
operator, dt, power, timestep_units='d')
cecm.integrate()

```

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**Author:** ![scaleuser](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/scaleuser/32/2904_2.png) [@scaleuser](https://openmc.discourse.group/u/scaleuser)\
**Post date:** [February 3, 2024, 1:28am UTC](https://openmc.discourse.group/t/difference-k-eff-transport-and-depletion-version-0-14-0/3884/2 "2024-02-03T01:28:20Z")

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Just noting that I also encountered this issue [here](https://openmc.discourse.group/t/higher-k-eff-at-0-depletion-step/3469/1).