# Accessing nubar nuclear data

**URL:** <https://openmc.discourse.group/t/accessing-nubar-nuclear-data/2609>\
**Category:** User Support\
**Created:** [January 12, 2023, 2:58pm UTC](https://openmc.discourse.group/t/accessing-nubar-nuclear-data/2609 "2023-01-12T14:58:43Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![tntfnc](https://avatars.discourse-cdn.com/v4/letter/t/f07891/32.png) [@tntfnc](https://openmc.discourse.group/u/tntfnc)\
**Post date:** [January 12, 2023, 2:58pm UTC](https://openmc.discourse.group/t/accessing-nubar-nuclear-data/2609/1 "2023-01-12T14:58:43Z")

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Hi,

I am trying to follow this notebook on OpenMC nuclear data, with the intent of modifying the nubar parameter for the isotope U-235 in the hdf5 ENDFB-VII.1 nuclear library:

[https://docs.openmc.org/en/v0.12.2/examples/nuclear-data.html](https://docs.openmc.org/en/v0.12.2/examples/nuclear-data.html)

however, the nubar MT=452 does not seem to be included in the U-235 reactions list. Where are these data stored and how should go about accessing them?

Many thanks,  
Francesco