# download JEFF library

**URL:** <https://openmc.discourse.group/t/download-jeff-library/526>\
**Category:** User Support\
**Created:** [December 12, 2019, 6:10pm UTC](https://openmc.discourse.group/t/download-jeff-library/526 "2019-12-12T18:10:49Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Rachel\_Reifer](https://avatars.discourse-cdn.com/v4/letter/r/f08c70/32.png) [@Rachel\_Reifer](https://openmc.discourse.group/u/Rachel_Reifer)\
**Post date:** [December 12, 2019, 6:10pm UTC](https://openmc.discourse.group/t/download-jeff-library/526/1 "2019-12-12T18:10:49Z")

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Hi!  
I am new to openmc and am trying to download the cross sections from the JEFF library. If anyone is able to help with how to do this, that would be great.

Thanks!

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**Author:** ![Javier\_Gonzalez](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/javier_gonzalez/32/1095_2.png) [@Javier\_Gonzalez](https://openmc.discourse.group/u/Javier_Gonzalez)\
**Post date:** [December 12, 2019, 6:20pm UTC](https://openmc.discourse.group/t/download-jeff-library/526/2 "2019-12-12T18:20:01Z")

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Hi Rachel, if you are using OpenMC 0.11.0, you can use this link to download JEFF libraries: [https://openmc.org/other-data-libraries/](https://openmc.org/other-data-libraries/).

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**Author:** ![Rachel\_Reifer](https://avatars.discourse-cdn.com/v4/letter/r/f08c70/32.png) [@Rachel\_Reifer](https://openmc.discourse.group/u/Rachel_Reifer)\
**Post date:** [December 12, 2019, 8:11pm UTC](https://openmc.discourse.group/t/download-jeff-library/526/3 "2019-12-12T20:11:34Z")

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Thank you!

Also, once I download them, is there now a way to convert the library to an XML file?

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**Author:** ![Javier\_Gonzalez](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/javier_gonzalez/32/1095_2.png) [@Javier\_Gonzalez](https://openmc.discourse.group/u/Javier_Gonzalez)\
**Post date:** [December 12, 2019, 8:29pm UTC](https://openmc.discourse.group/t/download-jeff-library/526/4 "2019-12-12T20:29:17Z")

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Once you download and extract them, you define in the “materials.xml” file where those cross sections are located, something like this:

materials = openmc.Materials([mat1, mat2, mat3])  
materials.cross\_sections = ‘/path/to/NuclearData/cross\_sections.xml’

materials.export\_to\_xml()

Hope this helps.  
Javier