# Generating a derived library using OpenMC and tools

**URL:** <https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468>\
**Category:** User Support\
**Created:** [September 17, 2026, 11:43pm UTC](https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468 "2026-09-17T23:43:08Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![alwonj7](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@alwonj7](https://openmc.discourse.group/u/alwonj7)\
**Post date:** [September 17, 2026, 11:43pm UTC](https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468/1 "2026-09-17T23:43:08Z")

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Hello everyone,

This is kind of related to OpenMC. I’ve been looking at cross sections and have used the openmc\_data repository to generate/merge cross section files. I have a question about trying to create a library for Spectra-PKA. I have a library supposedly derived from TENDL2025. I was wondering if I could use OpenMC or OpenMC-related tools to accomplish this. I tried looking up documentation on how to/what is included in terms of formatting, but I couldn’t find anything. This is a long shot, but does anyone have any experience with this? I’m looking to create my own spectra pka library because it is missing some nuclides. Thank you!

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**Author:** ![yrrepy](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/yrrepy/32/2365_2.png) [@yrrepy](https://openmc.discourse.group/u/yrrepy)\
**Post date:** [September 18, 2026, 6:36pm UTC](https://openmc.discourse.group/t/generating-a-derived-library-using-openmc-and-tools/6468/2 "2026-09-18T18:36:46Z")

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Hi Al,

I have a custom experimental workflow to produce FISPACT nuclear data files. But not Spectra-PKA. It mostly works with `njoy` and `prepro`, and nothing direct from OpenMC.

They’ve recently moved everything around on their website and so its hard to find stuff.  
[https://fispact.github.io/resources/nuclear\_data\_downloads/](https://fispact.github.io/resources/nuclear_data_downloads/)  
[https://fispact.github.io/utilities/spectra-pka/](https://fispact.github.io/utilities/spectra-pka/)

You could probably suss out from the TENDL-2023 PKA files how to make a new library with njoy, see below from their github

## **Input PKA data download[¶](https://fispact.github.io/utilities/spectra-pka/#input-pka-data-download "Permanent link")**

_`SPECTRA-PKA` uses NJOY-generated recoil cross section matrices. The output files required from NJOY are non-standard and are produced by a slightly modified version of the GROUPR module within NJOY. An evolving selection of databases produced using various international reaction cross section libraries (for various incident particle types) have been pre-calculated and are available to download as compressed tar archives — see the detailed listing of nuclear data for FISPACT-II (and `SPECTRA-PKA`) at [[1]](https://fispact.github.io/resources/nuclear_data_downloads/). **These can be used immediately with `SPECTRA-PKA`, or can be used as a template to guide users who may want to create their own input data files (for example, for libraries not currently included on the download page**)._