# Setting Cell Regions

**URL:** <https://openmc.discourse.group/t/setting-cell-regions/4163>\
**Category:** User Support\
**Created:** [April 15, 2024, 4:29pm UTC](https://openmc.discourse.group/t/setting-cell-regions/4163 "2024-04-15T16:29:36Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![trajan061](https://avatars.discourse-cdn.com/v4/letter/t/59ef9b/32.png) [@trajan061](https://openmc.discourse.group/u/trajan061)\
**Post date:** [April 15, 2024, 4:29pm UTC](https://openmc.discourse.group/t/setting-cell-regions/4163/1 "2024-04-15T16:29:36Z")

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Hello all! I am modeling a subcritical pile of graphite bricks with aluminum cladding. I have a .csv file that is reading the centers of each bricks and I keep getting a TypeError: Unable to set “cell region” to “\<RectangularParallelepiped at 0x7d160a279240\>” which is not of type “Region”. I’m not sure why I am getting this error

 ![SubCriticalPileCodeSnippet](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/f/f3f9ec1ceffc6b579ecae484df410efbfba30142.png)

Any help will be appreciated, thank you.

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**Author:** ![Daedalus](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/daedalus/32/2928_2.png) [@Daedalus](https://openmc.discourse.group/u/Daedalus)\
**Post date:** [April 15, 2024, 4:41pm UTC](https://openmc.discourse.group/t/setting-cell-regions/4163/2 "2024-04-15T16:41:49Z")

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[openmc.model.RectangularParallelepiped — OpenMC Documentation](https://docs.openmc.org/en/stable/pythonapi/generated/openmc.model.RectangularParallelepiped.html?highlight=Rectangular)

RectangularParallelepiped is not a region, it is a surface. You will need to define the graphite\_brick\_region as being inside the surfaces.