Andrea Saltos is a nuclear 🏷️#engineer whose neutronics work is published under a 📝Commonwealth Fusion Systems affiliation. The problem is counting the neutrons that get through — through meters of 📝shielding, through the penetrations cut in that shielding to admit diagnostics, and out of the building. Saltos is first author of two Transactions of the American Nuclear Society papers, on variance reduction for deep-penetration 📝Monte Carlo neutronics and on benchmarking the FNS skyshine experiment with the Attila deterministic solver.

Deep penetration is where the standard method fails. A Monte Carlo particle launched at a 📝14 MeV neutron source almost never survives to score a tally on the far side of a thick shield, so the estimator starves and the answer carries no useful statistics; variance reduction techniques bias the transport to feed it, and deterministic solvers such as Attila avoid the sampling problem entirely by solving the transport equation on a mesh. Benchmarking that machinery against an experiment whose answer was measured is how it earns the right to size real walls. Saltos has applied it to 📝SPARC — shielding models for the fusion facility, deterministic analysis of a deep shield with penetrations, and the neutronics behind the placement and calibration of SPARC's neutron flux monitors, part of the machine's 📝neutron diagnostics suite. These are design calculations for a tokamak that has not yet operated; the measurements that will test them do not exist yet.