Workflow & orchestration
FissionGeneral nuclearScientific computing

WATTS.

Workflow and Template Toolkit for Simulation

WATTS (Workflow and Template Toolkit for Simulation) is a small MIT-licensed Python library from Argonne for driving simulation codes from a script: it fills Jinja placeholders in a code's text input from a parameters mapping, runs the code in an isolated temporary directory, and files inputs, outputs and parameters into a local results database. Code-specific plugins add unit conversion and light post-processing.

Reference listingListedSources checked 2026-10-10
Engineering questions it helps answer
  • How does a result change when sweeping a geometry or material parameter across many runs without hand-editing input files?
  • How can temperatures from a systems code be handed to a Monte Carlo neutronics model and iterated in plain Python?
  • How can one physical quantity be kept in a single unit and converted correctly for codes that expect SI or CGS inputs?
Physics scope
  • Workflow orchestration around external codes (no physics of its own)
  • Jinja-templated input generation with strict undefined checking
  • Unit conversion to SI or CGS with astropy
  • Local results database of per-run inputs, outputs and parameters
  • Plugins for OpenMC, MCNP, Serpent, MOOSE applications, SAS, RELAP5, PyARC, Dakota and techno-economic tools

Limitations

Workflow logic is ordinary Python written by the user; there is no DAG engine, scheduler, remote execution or exit-code checking. The database is a directory of pickled Python objects rather than a shared store, several plugins target restricted codes, and the package is marked alpha with infrequent releases.

Fusion relevance

Not fusion-specific: bundled plugins and examples target fission systems. The OpenMC, MCNP and Serpent plugins and the generic text-template plugin can drive the transport codes used for fusion neutronics, and its unit handling and results database are code-agnostic.

Upstream examples

Published by the project itself. These are the project's own tutorials, not Morton Labs runs.

Reference workflows on this site

No reference workflow documents this tool yet. Its evidence status is “Listed”: A reviewed catalog entry with upstream links.

People
Editorial spotlight

Paul Romano

Computational scientist at Argonne National Laboratory; project lead of OpenMC; curator of Awesome Nuclear

Computational Scientist · Argonne National Laboratory

Awesome NuclearCardinalendf-pythonOpenMC
Paul RomanoAuthorHistorical · 2022–

First and corresponding author of the 2022 Journal of Open Source Software paper describing WATTS.

Evidence: joss.theoj.org · checked 2026-10-10
Paul RomanoMaintainerCurrent

Inferred from activity rather than a stated title: top committer, publisher of the v0.5.2 release (April 2025) and the account that merged the most recent change (July 2026). No official page names a maintainer.

Evidence: github.com · checked 2026-10-10

Roles name a specific relationship with evidence. Authorship of a paper is not maintainership, and a listed person is not a Morton Labs partner or endorser.

Source collections

This entry was written by Morton Labs from public sources and last checked on 2026-10-10. Spotted an error, or want something changed or removed? Email zach@mortonlabs.ai with the page address.

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