# Overlaping cell detected

**URL:** <https://openmc.discourse.group/t/overlaping-cell-detected/2062>\
**Category:** User Support\
**Created:** [May 23, 2022, 2:29am UTC](https://openmc.discourse.group/t/overlaping-cell-detected/2062 "2022-05-23T02:29:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![lei](https://avatars.discourse-cdn.com/v4/letter/l/7feea3/32.png) [@lei](https://openmc.discourse.group/u/lei)\
**Post date:** [May 23, 2022, 2:29am UTC](https://openmc.discourse.group/t/overlaping-cell-detected/2062/1 "2022-05-23T02:29:10Z")

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Hello everyone:

I am struggling with a strange problem. When I use 2,000,000 particles, it throws an error message, “overlapping cells detected: 36, 30 on universe 4”. However, When I use more or less particles. I have tested 4,000,000 particles and 100,000 particles. It seems everything works fine.

Following are my python scripts.  
[build\_xml.py](https://openmc.discourse.group/uploads/short-url/x19juUQ5IPE0xPb9ETbnOVnjvvi.py) (4.2 KB)  
[lattice.py](https://openmc.discourse.group/uploads/short-url/jhQbJoNRoYEZf8vZhwW3VB5OLjO.py) (25.7 KB)  
[materials.py](https://openmc.discourse.group/uploads/short-url/pNjQC8oYQj1IEvJcwNEo9DiKpAY.py) (49.5 KB)  
[tally.py](https://openmc.discourse.group/uploads/short-url/jilP70n2a9eDNxTLKJyA0n3T2fu.py) (1.6 KB)

 ![100000](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/0/015197ae72004a9bb2883912383af391afff8ddc.png)  
 ![2000000](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/9/9115f282373a71d0f5add9f9365c570e33395d38.png)  
 ![4000000](https://global.discourse-cdn.com/free1/uploads/openmc/original/2X/e/e95b9b2f09da2cc9097f4e5b89b8c1423f97026c.png)

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<div class="post-metadata">

**Author:** ![lei](https://avatars.discourse-cdn.com/v4/letter/l/7feea3/32.png) [@lei](https://openmc.discourse.group/u/lei)\
**Post date:** [May 23, 2022, 8:08am UTC](https://openmc.discourse.group/t/overlaping-cell-detected/2062/2 "2022-05-23T08:08:11Z")

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Supplement:

The previous version of openmc I ran was 0.12.0. It threw the issue I described above. But when I rebuild openmc into 0.13.0, it works fine, and doesn’t throw a similar issue. I still don’t know the reason why the openmc of version 0.12.0 throw such error.

Still hope some experienced user could check my python scripts about the geometry definition and especially about the tally definition, which I want to get the power production for each fuel assembly including fission and gamma heat. PS, this is a typical SFR core.

Thanks in advance.