# Getting compositions of fuel after depletion of full pebble bed core

**URL:** <https://openmc.discourse.group/t/getting-compositions-of-fuel-after-depletion-of-full-pebble-bed-core/3723>\
**Category:** User Support\
**Created:** [December 8, 2023, 5:20am UTC](https://openmc.discourse.group/t/getting-compositions-of-fuel-after-depletion-of-full-pebble-bed-core/3723 "2023-12-08T05:20:50Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Ranzo](https://avatars.discourse-cdn.com/v4/letter/r/ee7513/32.png) [@Ranzo](https://openmc.discourse.group/u/Ranzo)\
**Post date:** [December 8, 2023, 5:20am UTC](https://openmc.discourse.group/t/getting-compositions-of-fuel-after-depletion-of-full-pebble-bed-core/3723/1 "2023-12-08T05:20:50Z")

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Hello,

I am new to OpenMC. I want to perform a full core depletion of a pebble bed reactor and obtain the compositions of pebbles at different zones in the core. I am not sure if i need to define different material with number equal to that of the core zones, or i need to identify multiple cells in the core?  
If both work, which one can run faster?

In addition, how can i extract the compositions at different zones and at different burnup steps after depletion.