# Cannot define region from hexagonal lattice boundary to a cylinder

**URL:** <https://openmc.discourse.group/t/cannot-define-region-from-hexagonal-lattice-boundary-to-a-cylinder/3142>\
**Category:** User Support\
**Created:** [June 24, 2023, 4:39pm UTC](https://openmc.discourse.group/t/cannot-define-region-from-hexagonal-lattice-boundary-to-a-cylinder/3142 "2023-06-24T16:39:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![mosharat25](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/mosharat25/32/2650_2.png) [@mosharat25](https://openmc.discourse.group/u/mosharat25)\
**Post date:** [June 24, 2023, 4:39pm UTC](https://openmc.discourse.group/t/cannot-define-region-from-hexagonal-lattice-boundary-to-a-cylinder/3142/1 "2023-06-24T16:39:24Z")

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Hello, everyone.

I have been trying to define the region outside a hexagonal lattice and inside a cylinder surrounding the lattice. I want the command to be like this:

```
         +hexagonal lattice periphery & -cylinder radius 

```

I also want to fill this region with some material. I cannot however, come up with a geometry that will help with this.

- thanks in advance

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<div class="post-metadata">

**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\
**Post date:** [June 26, 2023, 1:34pm UTC](https://openmc.discourse.group/t/cannot-define-region-from-hexagonal-lattice-boundary-to-a-cylinder/3142/2 "2023-06-26T13:34:45Z")

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It sounds like your issue has already been solved in another thread?

> [@\[help needed\] HexLattice does not intersect with ZCylinder](https://openmc.discourse.group/t/help-needed-hexlattice-does-not-intersect-with-zcylinder/419/4):
>
> Solved, thank you. -Mosharat

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<div class="post-metadata">

**Author:** ![mosharat25](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/mosharat25/32/2650_2.png) [@mosharat25](https://openmc.discourse.group/u/mosharat25)\
**Post date:** [June 26, 2023, 3:41pm UTC](https://openmc.discourse.group/t/cannot-define-region-from-hexagonal-lattice-boundary-to-a-cylinder/3142/3 "2023-06-26T15:41:28Z")

</div>

While that issue has been solved, I still cannot place any other geometry in between the hexagon and the cylinder, any other geometry placed there seems to be overlapping.

If I assign the outer universe of the Hexlattice as a universe containing any other shape, it does not show there. For example, if I want to place a water hole outside of the hexagonal core,

Outer =openmc.Universe(cells=()) #outer universe containing cells of water holes

Hexlattice.outer = Outer

The outer region of the hexagonal lattice does not show the water holes when plotted and even if they show up through some geometry tweaking, they seem to be overlapping.