The SPARC neutronics and shielding papers are seven Transactions of the American Nuclear Society conference proceedings, published in 2022 and 2023, in which Commonwealth Fusion Systems engineers and their MPR Associates collaborators set out how the neutron environment around 📝SPARC is calculated and shielded against.
This memo exists because conference proceedings appear nowhere in CFS's own publication index, which lists journal articles only. An entire branch of the company's nuclear engineering record — the branch a regulator or a facility designer would want first — is therefore invisible from the company's own pages. The American Nuclear Society deposits no abstracts with its DOIs, so what follows describes each paper's scope from its title, volume and pages. No result from any of the seven is asserted here.
Five are method papers. 📝Andrea Saltos led an evaluation of variance reduction techniques for deep penetrations in fusion neutronics (127, 238–241, 2022) with Ethan Peterson of the 📝MIT Plasma Science and Fusion Center, Dominic Napolitano, Ryanne Kennedy and Andrew Hodgdon; deep penetration is the hard case for 📝Monte Carlo neutronics, because almost no simulated particles survive to the far side of a thick 📝shielding wall unless the sampling is biased toward the ones that do. Jackson Stanley led the implementation of temperature-dependent cross sections for flux and heat deposition analysis (129, 284–287, 2023). Austin Carter led a CAD-based approach to fusion neutronics simulation (129, 280–283, 2023), which is the geometry-handling problem: a tokamak's as-built CAD model must become a solvable transport geometry without hand translation. Michael Saitta of MPR Associates led a deterministic analysis of a deep shield with penetrations (129, 288–291, 2023), and Saltos led a benchmark of the Japanese FNS skyshine experiment using the Attila deterministic solver (129, 292–295, 2023) — skyshine being 📝neutron flux that leaves a facility, scatters off the atmosphere and returns to ground beyond the walls.
Two are SPARC-specific. Ian Miner led "Shielding Design of SPARC Diagnostic Ports: Practical Lessons" (128, 155–158, 2023), and Joshua Jones of MPR Associates led the neutronics models for evaluating shielding in the SPARC facility (129, 1051–1054, 2023). Ports are where shields are weakest — every diagnostic sightline is a hole through the biological shield, and the streaming paths it opens drive both 📝activation analysis of the surrounding structure and the 📝radiation hardening requirements on the instruments themselves. Ryanne Kennedy, of MPR Associates on all of these, is a co-author on six of the seven.
Four-page conference papers are where we put SPARC's neutronics methods in front of the nuclear engineering community rather than the plasma physics one.