# Nested Lattice and 3D Lattice

**URL:** <https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261>\
**Category:** User Support\
**Created:** [March 16, 2017, 2:58pm UTC](https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261 "2017-03-16T14:58:42Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Mark\_Smith](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Mark\_Smith](https://openmc.discourse.group/u/Mark_Smith)\
**Post date:** [March 16, 2017, 2:58pm UTC](https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261/1 "2017-03-16T14:58:42Z")

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Good afternoon, as part of an assignment I am modelling a number of barrels filled with tubes of fuel.

I’ve used the hex\_lattice to model a single barrel to a tea (see delightfully garish pic “1\_plot”). This is currently a 3D shape.

I am looking to construct this as a 2 x 2 x 2 lattice as per the second picture attached.

In setting up the 2D 2 x 2 lattice of the system - The individual barrels clear out a “void” area around them that I haven’t defined (see attached - “2 x 2 result”). The “Outer” term is defined but this does not seem to be affecting this. Any thoughts on this?

Geometry code is in the attached XML - thanks for any help you can offer.

Thanks Mark

 ![1_plot.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/cbf9dd4bb88bd4a738510c740c455a51cb2b84f2.png)

![Intended 2 x 2 x 2 config.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/c3cb9371ebc4cc613d939e1915020e436ff67460.png)

 ![2 x 2 result.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/3ab7090c0777ab42219a48f24d50b656476b5f77.png)

[Single Barrel Geometry v01.xml](https://openmc.discourse.group/uploads/short-url/v2DGPjdFdFImM3HXaM4JFDayN5o.xml) (2.19 KB)

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<div class="post-metadata">

**Author:** ![Mark\_Smith](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Mark\_Smith](https://openmc.discourse.group/u/Mark_Smith)\
**Post date:** [March 16, 2017, 3:56pm UTC](https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261/2 "2017-03-16T15:56:28Z")

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I’ve cleaned this up to see the wood from the trees (see attached image) but this persists in clearing out the full zone equal to the pitch distance. Is this correct?

 ![1_plot.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/2b02a944a68b45764191c503e3d20405cf8bbc84.png)

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<div class="post-metadata">

**Author:** ![Mark\_Smith](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Mark\_Smith](https://openmc.discourse.group/u/Mark_Smith)\
**Post date:** [March 17, 2017, 11:39am UTC](https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261/3 "2017-03-17T11:39:20Z")

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RESOLVED. I needed to set a fill for the universe outside of the barrel. Attached is both XML and pics.

 ![Profile.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/d738bf9466f085b6ed0ec5f6ac17202fbb84c826.png)

 ![Aerial.png](https://global.discourse-cdn.com/free1/uploads/openmc/original/1X/a204a0a36bb5ac71587a90d003ef5cb195bb4680.png)

[4 Barrel 2D Lattice Geometry v02 - CURRENT VERSION.xml](https://openmc.discourse.group/uploads/short-url/3kiPEpITiGVNiHS4qDss3SNvtz7.xml) (2.81 KB)

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**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:** [March 17, 2017, 12:20pm UTC](https://openmc.discourse.group/t/nested-lattice-and-3d-lattice/261/4 "2017-03-17T12:20:48Z")

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I was just in the middle of writing you a reply – glad that you were able to figure it out!