Sandy

<p align="center"> <img src="./badges/python.svg" alt="Python version"> <a href="https://travis-ci.org/luca-fiorito-11/sandy"> <img src="https://travis-ci.org/luca-fiorito-11/sandy.svg?branch=master" alt="Build status"> </a> <a href="https://opensource.org/licenses/MIT"> <img src="https://img.shields.io/badge/License-MIT-yellow.svg" alt="License: MIT"> </a> <!--- <a href="http://hits.dwyl.io/luca-fiorito-11/sandy"> <img src="http://hits.dwyl.io/luca-fiorito-11/sandy.svg" alt="HitCount"> </a> --> <a href="https://coveralls.io/github/luca-fiorito-11/sandy"> <img src="https://coveralls.io/repos/github/luca-fiorito-11/sandy/badge.svg" alt="Coverage Status"> </a> </p> <h1 align="center" style="font-family:simplifica">SANDY</h1> <h5 align="center">Sampling tool for nuclear data</h5> <br>

SANDY is a python package that can read, write and perform a set of operations on nuclear data files in ENDF-6 format.

Stochastic sampling of nuclear data

The primary objective of the code, as it was originally conceived, is to produce perturbed files containing sampled parameters that represent the information stored in the evaluated nuclear data covariances. Such files can be ultimately used to propagate uncertainties through any given compatible system using a brute force technique.

Currently, SANDY can draw samples for:

• cross sections;
• energy distrbutions of outgoing particles;
• fission neutron multiplicities;
• fission yields;
• radioactive decay data.

API for ENDF-6 files

The recent development on SANDY extended the original goal and focused on providing a simple interface for nuclear data files in ENDF-6 format. Nuclear data such as cross sections, fission yields, radioactive decay constants and so on can be imported into tabulated dataframes (making extensive use of pandas) for further post-processing, analysis, plotting, ...

Examples are available here.

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:wrench: Installation

SANDY can be installed both on Linux (recommended) or Windows. The installation instructions are available here.

:exclamation: Try the installation procedure on a dedicated environment by clicking the badge below (see also this github repository).

<p align="center"> <a href="https://github.com/codespaces/new?hide_repo_select=true&ref=main&repo=luca-fiorito-11/sandy_install"> <img src="https://img.shields.io/badge/Start%20SANDY%20Install-Codespaces-green?logo=github"> </a> </p> <br>

:hourglass: Development history and releases

The latest and older releases of SANDY are available here.

For a detailed list of changes across versions, please refer to the CHANGELOG file.

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:computer: Try out the SANDY workshop

The materials for a hands‑on workshop given at PHYSOR2026 was collected in a github repository.

To try it out, click the badge below and launch the full environment in your browser — no installation needed.

<p align="center"> <a href="https://github.com/codespaces/new?hide_repo_select=true&ref=main&repo=luca-fiorito-11/sandy_workshop"> <img src="https://img.shields.io/badge/Open%20Workshop%20Environment-Codespaces-blue?logo=github" alt="Start SANDY Workshop in Codespaces"> </a> </p> <br>

:notebook_with_decorative_cover: Documentation and how to use SANDY

The official SANDY documentation can be found here.

The primary use for SANDY is to produce perturbed nuclear data files that statistically represent the covariance information found in evaluated libraries. This can be done using a command line interface.

Example for cross sections, nubar and pfns sampling

# Produce ENDF-6 / PENDF perturbed files
python -m sandy.sampling  U235.jeff33  --processes 20  --samples 200

# Produce ACE perturbed files
python -m sandy.sampling  U235.jeff33  --processes 20  --samples 200  --acer  --temperatures 900 

For a more advanced use, look at these notebooks:

• Direct sampling procedure: produce random ENDF-6 / ACE files
• 2-step sampling procedure

Example for radioactive decay data sampling

python -m sandy.sampling  decay_data.jeff33  --processes 20  --samples 200

Example for fission yield data sampling

# Only variance
python -m sandy.sampling nfy.jeff33 --processes 20 --samples 200

# With CEA covariance matrices for U235th and Pu239th 
python -m sandy.sampling nfy.jeff33 --processes 20 --samples 200  --fycov

For a more advanced use, look at these notebooks:

• FY Sampling: create perturbed FY files (only variance, all energies)
• FY sampling: create perturbed FY files with ad-hoc covariance matrix (all energies)
• FY sampling: create perturbed FY files using CEA conservative evaluation for U-235 thermal fission
• FY sampling: create perturbed FY files using CEA conservative evaluation for Pu-239 thermal fission

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:video_game: Jupyter notebooks

Here you can find some cool Jupyter notebooks that kind of give an idea of what one can do with SANDY.

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:telephone_receiver: Contacts

Luca Fiorito

• lucafiorito.11@gmail.com
• luca.fiorito@sckcen.be

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:bookmark: Acknowledgments

SANDY was conceived and developed as a part of the PhD thesis on Nuclear data uncertainty propagation and uncertainty quantification in nuclear codes in the framework of a collaboration between SCK CEN and ULB.

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:clipboard: Reference

Among the publications about SANDY, please use the following as references for citation.

Burnup analysis

• L. Fiorito, L. Engelen, F. Grimaldi, P. Romojaro, Nuclear data uncertainty propagation in the ARIANE GU3 burnup model using SANDY: Comparison between a FA and a pincell model, Annals of Nuclear Energy, Volume 218, 2025, 111423, ISSN 0306-4549.

Criticality

• L. Fiorito, J. Dyrda and M. Fleming, JEFF-3.3 covariance application to ICSBEP using SANDY and NDAST, EPJ Web of Conferences 211, 07003 (2019)

Original publication

• L. Fiorito, G. Žerovnik, A. Stankovskiy, G. Van den Eynde, P.E. Labeau, Nuclear data uncertainty propagation to integral responses using SANDY, Annals of Nuclear Energy, Volume 101, 2017, Pages 359-366, ISSN 0306-4549.

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:earth_africa: Publications

This is a (incomplete) list of scientific studies citing SANDY.

• Ebiwonjumi, Bamidele. Uncertainty Analyses of Tritium Production and Gamma Heating Rates in. FUSION SCIENCE AND TECHNOLOGY, 2025. Article; Early Access, Vol. N/A. DOI
• Delipei, Gregory K.. Uncertainty Quantification Framework for High-Temperature Gas-Cooled. NUCLEAR SCIENCE AND ENGINEERING, 2025. Article; Early Access, Vol. N/A. DOI
• Yaseen, Mahmoud. Sensitivity and uncertainty analysis in pebble-bed reactors: A study. ANNALS OF NUCLEAR ENERGY, 2025. Article, Vol. 219. DOI
• Fiorito, Luca. Nuclear data uncertainty propagation in the ARIANE GU3 burnup model. ANNALS OF NUCLEAR ENERGY, 2025. Article, Vol. 218. DOI
• Ryzhkov, Alexander A.. A review of the current nuclear data performance assessments in advanced. ANNALS OF NUCLEAR ENERGY, 2025. Review, Vol. 212. DOI
• Lovecky, M.. OPOS-1000: Advancing the efficiency of VVER-1000 spent nuclear fuel cask. NUCLEAR ENGINEERING AND DESIGN, 2025. Article, Vol. 431. DOI
• Dagan, R.. Investigation of nuclide inventory of cladding material irradiated in. ANNALS OF NUCLEAR ENERGY, 2025. Article, Vol. 212. DOI
• Lovecky, M.. Optimizing spent nuclear fuel cask loading for VVER-440 fuel. NUCLEAR ENGINEERING AND TECHNOLOGY, 2024. Article, Vol. 56. DOI
• Osman, W.. AN INTEGRATED FRAMEWORK FOR UNCERTAINTY QUANTIFICATION IN HIGH. Arxiv, 2024. preprint, Vol. N/A. DOI
• Jo, YuGwon. Uncertainty quantification based on similarity analysis of reactor. NUCLEAR ENGINEERING AND TECHNOLOGY, 2024. Article, Vol. 56. DOI
• Zu, Tiejun. Development and Verification of Sampling Code NECP-SOUL for Evaluated. NUCLEAR SCIENCE