Introduction to SCONE

What is SCONE?

SCONE (Stochastic Calculator Of Neutron Transport Equation) is a Monte Carlo code from the University of Cambridge for neutron transport in nuclear systems. It samples neutron histories from birth through collision, absorption, or escape—continuous-energy cross sections, CSG geometry, eigenvalue and fixed-source workflows, and OpenMP via OMP_NUM_THREADS.

The codebase is Fortran 2008+ with a modular layout: good for graduate coursework, thesis work, and extending physics or tallies in source. It is MIT-licensed with no export-control restrictions on obtaining the code.

Contributors & acknowledgments

SCONE was developed at the University of Cambridge under the supervision of Dr. Eugene Shwageraus. Core development has been led by Dr. Mikolaj Kowalski and Dr. Valeria Raffuzzi, with Dr. Paul Cosgrove and others extending physics, geometry, and methods. Alex Bland and the wider Cambridge Nuclear Energy group continue to maintain and apply SCONE in research and teaching.

Repositories and files for these tutorials

Two different GitHub repos matter: the SCONE program you build and run, and the example inputs this guide displays (and mirrors for download).

• SCONE source code — github.com/CambridgeNuclear/SCONE. Fortran/CMake tree; clone here, compile, then execute scone.out (or your build name) against .inp-style dictionary inputs. This repo does not hold the ReactorMC tutorial decks.
• Public examples mirror — github.com/caalh/ReactorMC. Same scone-examples/ layout as in the ReactorMC website repository: runnable SCONE inputs you can copy or clone, plus OpenMC scripts in a sibling folder.

Layout under caalh/ReactorMC (SCONE parts relevant to this guide)

ReactorMC/                    ← org repo root
├── scone-examples/
│   ├── verify/                 ← testLib decks; run via run_all.ps1 (see verify/README.md)
│   │   ├── tutorial_*          ← individual inputs (no file extension)
│   │   ├── run_all.ps1
│   │   └── VERIFICATION_SUMMARY.md
│   ├── scone_beavrs_clean.inp  ← full BEAVRS-style deck (needs full ACE, not testLib)
│   └── README_BEAVRS_PARITY.md
└── openmc-examples/            ← Python; separate from SCONE inputs

On this site, many pages pull verified listings straight from scone-examples/verify/ so the text cannot drift from the file that was run. Each code block has a footer linking to the matching path on caalh/ReactorMC and stating whether it is in the testLib harness, an excerpt, production-style, or a tutorial-only snippet.

Topic pages map loosely to those files: e.g. assembly geometry and the hub deck appear under Reactor Examples and Examples; shielding slabs under Shielding Examples; BEAVRS under BEAVRS. The exact filename for a block is always given in the footer when it exists on the mirror.

Using this guide

If you are new to SCONE, follow the sidebar in order: Installation, Basics (walk-through deck), Geometry, Materials, and Simple Examples. Then open Tallies, Settings, and any other topic pages as you need them.

Decks use dictionary-style input: semicolon-terminated keys and nested { } blocks. The upstream manual explains the rules under Dictionary Input.

On this site, “replay” means reproducibility (not video). For examples we identify as verified, we ran the full input in SCONE using the compact ACE library that ships with SCONE for integration tests—point SCONE_ACE at that library the same way SCONE’s own test workflow does. The listings on those pages are the decks we executed. Anything that is not meant to be run that way—production evaluated libraries, excerpts, or illustrations—is called out in the page text so we do not imply every code block went through the same check. See Repositories and files for these tutorials above for where those decks live on GitHub and how they map to this guide.

The BEAVRS chapter is reviewed so it stays aligned with our reference SCONE deck; you only need SCONE and the official BEAVRS documentation to follow along, not any private source tree.

Next steps

SCONE is used for pin and assembly eigenvalue problems, lattice physics, and method development—including BMP-style geometry checks via viz. For licensing-scale production work, established codes such as MCNP or Serpent remain the common choice.