# Could not find nuclide U-235.70c in cross\_sections.xml file!

**URL:** <https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86>\
**Category:** User Support\
**Created:** [June 21, 2014, 12:04am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86 "2014-06-21T00:04:45Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Otman](https://avatars.discourse-cdn.com/v4/letter/o/7c8e57/32.png) [@Otman](https://openmc.discourse.group/u/Otman)\
**Post date:** [June 21, 2014, 12:04am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/1 "2014-06-21T00:04:45Z")

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hi,  
i have this error  
Reading settings XML file…  
Reading cross sections XML file…  
Reading geometry XML file…  
Reading materials XML file…  
ERROR: Could not find nuclide U-235.70c in cross\_sections.xml file!  
ERROR STOP  
regards

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**Author:** ![Derek\_Lax1](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Derek\_Lax1](https://openmc.discourse.group/u/Derek_Lax1)\
**Post date:** [June 21, 2014, 12:09am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/2 "2014-06-21T00:09:29Z")

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Hi,

If you used the NNDC cross section python script, try replacing the 70c with 71c.

Best,  
Derek

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**Author:** ![Derek\_Lax1](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Derek\_Lax1](https://openmc.discourse.group/u/Derek_Lax1)\
**Post date:** [June 21, 2014, 1:25am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/3 "2014-06-21T01:25:40Z")

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Hi Otman,

Is this a test or example you are running or is it your own file? Also, I’ve readded the google group as this is not my area of expertise. Hopefully someone who deals with cross sections can weigh in on this.

Best,  
Derek

[materials.xml](https://openmc.discourse.group/uploads/short-url/k5vowjOGoWgIJhDzM5EPnaDnovE.xml) (378 Bytes)

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**Author:** ![walshjon](https://avatars.discourse-cdn.com/v4/letter/w/cdc98d/32.png) [@walshjon](https://openmc.discourse.group/u/walshjon)\
**Post date:** [June 21, 2014, 1:57am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/4 "2014-06-21T01:57:37Z")

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The NNDC data has a different labeling scheme than that of the data shipped with MCNP. It looks like you’ll want to use “HH2O” and “71t” in place of “lwtr” and “10t,” respectively.

That is, in the case of the pin cell example problem, try instead of .

Jon

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<div class="post-metadata">

**Author:** ![Derek\_Lax1](https://avatars.discourse-cdn.com/v4/letter/d/3bc359/32.png) [@Derek\_Lax1](https://openmc.discourse.group/u/Derek_Lax1)\
**Post date:** [June 21, 2014, 2:04am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/5 "2014-06-21T02:04:47Z")

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To those in charge of maintaining the test directory,

If this is from the test\_basic, is there a reason that this test doesn’t work out of the box?

Derek

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<div class="post-metadata">

**Author:** ![Otman](https://avatars.discourse-cdn.com/v4/letter/o/7c8e57/32.png) [@Otman](https://openmc.discourse.group/u/Otman)\
**Post date:** [June 21, 2014, 9:07am UTC](https://openmc.discourse.group/t/could-not-find-nuclide-u-235-70c-in-cross-sections-xml-file/86/6 "2014-06-21T09:07:56Z")

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Hi,  
thank you for your help. now the tests are working.  
regards