endf-userpy 0.1.0a2

High-level interpretation of ENDF-6 data

endf-userpy

High-level interpretation of ENDF-6 nuclear data files.

endf-userpy is a Python library that answers user-friendly questions about ENDF-6 nuclear data evaluations: "what is the cross section of the (n,2n) reaction on Fe-56?", "what is the energy spectrum of neutrons emitted from U-238 at 14 MeV?", "how much Co-60m is produced per (n,gamma) reaction on Co-59?".

The library does not parse ENDF-6 itself. It builds on endf_parserpy, which turns an ENDF-6 file into a nested Python dict (endf_dict). endf-userpy then walks that dict to reconstruct cross sections, yields, and differential distributions, hiding which MF section a piece of data lives in.

Status. This is an early alpha release. The public API is stabilising but may still change. See "Known limitations" below. Feedback by creating issues is appreciated.

Installation

pip install endf-userpy

Prebuilt wheels are available for cpython 3.9–3.13 on:

• Linux x86_64 (manylinux_2_28)
• macOS arm64 (>= 14.0)
• macOS x86_64 (>= 15.0)
• Windows AMD64

Other platforms or Python versions install from the sdist automatically and need a Fortran compiler (gfortran) on PATH.

Runtime dependencies (numpy, scipy, endf_parserpy) are pulled in automatically. Some examples additionally use matplotlib.

From source

git clone https://github.com/IAEA-NDS/endf-userpy
cd endf-userpy
pip install -e .

Requires gfortran on PATH. Windows users who prefer to build with the Intel Fortran compiler (ifx) can opt in by setting ENDF_USERPY_USE_IFX=1 in the environment before pip install.

Quick start

import numpy as np
from endf_parserpy import EndfParserFactory
from endf_userpy.quantities import (
    get_available_reactions,
    get_reaction_xs,
)

parser = EndfParserFactory.create()
endf_dict = parser.parsefile("tests/data/n-004_Be_009.endf")

print(get_available_reactions(endf_dict))
# ['(n,total)', '(n,n_0)', '(n,nonelas)', '(n,2n)', '(n,g)', ...]

eincs = np.array([0.0253, 1e3, 1e6, 1.4e7])  # eV
print(get_reaction_xs(endf_dict, "(n,total)", eincs))
# [6.154 6.144 3.341 1.528]   barn

Public API

All user-facing functions live in endf_userpy.quantities and take an endf_dict (already parsed) plus user-friendly string identifiers.

Function	Returns	What it does
get_available_reactions(endf_dict)	list of reaction strings	introspect a file
get_incident_energies(endf_dict, reaction)	array	tabulated Einc mesh for a channel
get_emission_energies(endf_dict, reaction, particle)	array	tabulated Eout mesh
get_reaction_xs(endf_dict, reaction, eincs)	array	cross section of a named channel
get_residual_production_xs(endf_dict, residual, eincs)	array	production of a specific residual nucleus, isomer-resolved
get_particle_production_xs(endf_dict, reaction, particle, eincs)	array	ejectile production cross section
get_particle_production_dxs_dE(endf_dict, reaction, particle, eincs, eouts)	array	dσ/dE energy spectrum of emitted particle
get_particle_production_dxs_dmu(endf_dict, reaction, particle, eincs, mus)	array	dσ/dΩ angular distribution
get_particle_production_ddxs(endf_dict, reaction, particle, eincs, eouts, mus)	array	d²σ/dE/dΩ double-differential

Reaction strings: "(n,total)", "(n,n_0)" (elastic), "(n,2n)", "(n,g)" (capture), "(n,p)", "(n,a)", etc. Particles: "n", "p", "d", "t", "h" (helium-3), "a" (alpha), "g" (gamma). Residual nuclei: "Z-Sym-A" (e.g. "27-Co-60") or "Sym-A" (e.g. "Co-60"), with optional isomer suffix g, m, m1, m2, ... ("Co-60m" = first metastable).

Examples

Seven runnable examples in examples/:

File	What it shows
01_inspect_file.py	discover what is in a file
02_reaction_xs.py	cross sections of named channels with consistency check
03_particle_production_xs.py	secondary-particle production from Fe-56
04_residual_production_isomers.py	Co-58g/m and Co-60g/m via (n,2n) and (n,gamma)
05_emission_spectra_14mev.py	classic 14 MeV neutron emission spectrum from U-238
06_ddx_uranium_14mev.py	double-differential cross section heatmap
07_photonuclear_residuals.py	(g,Nn) cascade on Au-197

Examples 1-2 use a small file shipped under tests/data/. Examples 3-7 each include the wget command to fetch the JENDL-5 file they need.

Known limitations

• No resonance reconstruction. MF2 (resolved/unresolved resonance parameters) is not reconstructed. For evaluations whose MF3 is empty in the resonance region, pre-process the file with NJOY RECONR and pass the PENDF file in.
• DDX drops kinematic-delta channels. The double-differential API silently skips elastic and discrete-level inelastic channels because they cannot be represented on a continuous Eout grid. They appear in the 1D dσ/dE spectrum as sharp peaks instead.
• Stubs. endf_userpy/discrete_quantities.py and endf_userpy/translation.py are work-in-progress sketches; do not rely on them.

Filing issues

github.com/IAEA-NDS/endf-userpy/issues

License and copyright

endf-userpy is distributed under the MIT license, see the LICENSE file for details.

Nothing in this license shall be construed as a waiver, either express or implied, of any of the privileges and immunities accorded to the IAEA by its Member States.

Copyright (c) 2026 International Atomic Energy Agency