# How to convert the time step of OpenMC 2D depletion calculation from day/second to burn-up depth (MWth/TU)

**URL:** <https://openmc.discourse.group/t/how-to-convert-the-time-step-of-openmc-2d-depletion-calculation-from-day-second-to-burn-up-depth-mwth-tu/860>\
**Category:** User Support\
**Created:** [November 12, 2020, 11:10am UTC](https://openmc.discourse.group/t/how-to-convert-the-time-step-of-openmc-2d-depletion-calculation-from-day-second-to-burn-up-depth-mwth-tu/860 "2020-11-12T11:10:15Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![wangyahui](https://avatars.discourse-cdn.com/v4/letter/w/df705f/32.png) [@wangyahui](https://openmc.discourse.group/u/wangyahui)\
**Post date:** [November 12, 2020, 11:10am UTC](https://openmc.discourse.group/t/how-to-convert-the-time-step-of-openmc-2d-depletion-calculation-from-day-second-to-burn-up-depth-mwth-tu/860/1 "2020-11-12T11:10:15Z")

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Hi all,

Can anybody tell me how to convert the time step of OpenMC 2D depletion calculation from day/second to burn-up depth (MWth/TU)?

Best,  
Yahui Wang

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**Author:** ![kingyue](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/kingyue/32/507_2.png) [@kingyue](https://openmc.discourse.group/u/kingyue)\
**Post date:** [November 13, 2020, 6:00am UTC](https://openmc.discourse.group/t/how-to-convert-the-time-step-of-openmc-2d-depletion-calculation-from-day-second-to-burn-up-depth-mwth-tu/860/2 "2020-11-13T06:00:15Z")

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Burnup depth(MWh/tU) = Power density(MW/tU) \* Time(h)  
You can get the time step by dividing the burnup depth step by the power density.

Note that in [OpenMC v0.12](https://docs.openmc.org/en/stable/releasenotes/0.12.0.html?highlight=MWd%2Fkg#new-features), depletion integrator classes now allow a user to specify timesteps in several units (s, min, h, d, MWd/kg). You just need to convert MWh/tU to MWd/kg.

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<div class="post-metadata">

**Author:** ![wangyahui](https://avatars.discourse-cdn.com/v4/letter/w/df705f/32.png) [@wangyahui](https://openmc.discourse.group/u/wangyahui)\
**Post date:** [November 13, 2020, 7:26am UTC](https://openmc.discourse.group/t/how-to-convert-the-time-step-of-openmc-2d-depletion-calculation-from-day-second-to-burn-up-depth-mwth-tu/860/3 "2020-11-13T07:26:23Z")

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Thank you Yue，thank you for your kind reply.