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Use the desktop

The desktop edits a single-material problem, runs the shared ACTINV solver in the background, and displays inventories, activity, heat, photon spectra, and pathways.

Install it from the download page. Published preview packages and current source builds can expose different features; see Versions and releases.

Learn without downloading nuclear data

In Overview & data, choose Try offline results tutorial. It shows a fictional one-hour decay example for learning the interface. Use the iron problem with verified data for an evaluated calculation.

Run a problem

  1. In Overview & data, keep the iron example or choose Open problem.
  2. Choose your installed activation and decay files, or download the standard neutron data and apply the installed paths.
  3. Check Input base. Relative file paths use this folder. Opening a JSON problem sets the base to its directory; older repository examples may need the repository root.
  4. Review Material, Irradiation & cooling, and Spectrum. A zero schedule multiplier means cooling. Spectrum values are integrated group fluxes, with explicit ordering and normalization.
  5. Choose optional outputs in Calculation options & requested outputs. Apply or discard advanced JSON edits before returning to structured editing.
  6. Choose Validate, then Run. The background task reports preparation and solving. In current builds, cancelling a calculation stops its isolated worker without publishing a partial result.

The current desktop uses a private prepared-data cache for each calculation, so setup time can recur between runs. CLI cache behavior is described in Data setup.

Explore and save results

In Results, choose activity, heat, or inventory, then select a computed time step. Filter and select a nuclide to follow its history. Heat remains the whole-material response. Add another result for a comparison; check both files’ physical times and normalizations.

Open Spectra & pathways for optional source information and Ledger & certificate for incomplete inputs and calculation details. Export the full result JSON to preserve the complete calculation. Inventory CSV contains the selected time step; saving the problem or exporting CSV does not save the full result.

Guided help

Choose Help or press F1 for setup and result walkthroughs. Use Back, Next, or Exit, and press Escape to close a tour. Ctrl/Cmd+O opens a problem and Ctrl/Cmd+S saves it.

Mesh runs, bulk library building, and transport-source exports use the CLI. Read Results for interpretation and Troubleshooting for input problems.