yamc-core

Yet Another Monte Carlo: neutron and photon transport for fusion neutronics. Constructive solid and mesh geometry, coupled neutron-photon transport, CAD import, flexible tallies and transport-coupled transmutation, with the whole solver in Rust.

This is the compiled distribution, and it provides the yamc module itself, so the import name and the distribution name differ (as pillow provides PIL). Install yamc rather than this: it pins the matching version of this wheel and is where the documentation lives.

import yamc

# A point source inside a Li/Be sphere.
inner = yamc.Sphere(x0=0, y0=0, z0=0, radius=1.0)
outer = yamc.Sphere(x0=0, y0=0, z0=0, radius=200.0, boundary="vacuum")

breeder = yamc.Material(
    composition={"Li6": 0.035, "Li7": 0.465, "Be9": 0.5},
    density=2.0,
    temperature=294,
)
breeder.read_nuclear_data({
    "Be9": "tests/Be9.arrow",
    "Li6": "tests/Li6.arrow",
    "Li7": "tests/Li7.arrow",
})

void = yamc.Cell(name="void", region=inner.below)
blanket = yamc.Cell(name="blanket", region=inner.above & outer.below, material=breeder)
geometry = yamc.Geometry([void, blanket])

source = yamc.NeutronSource(
    energy=yamc.sources.fusion_neutron_spectrum(20000.0),
    position=(0, 0, 0),
)
tally = yamc.Tally(name="tbr", cells=blanket, scores=["H3-production"])

model = yamc.Model(geometry=geometry, tallies=[tally], source=source)
results = model.simulate_transport(total_particles=250_000, seed=1)
print(results[tally].mean)

Relationship to yani

yamc is a superset: it ships everything yani has (materials, decay data, irradiation schedules, inventories) plus neutron and photon transport, geometry, tallies and transport-coupled transmutation. The two are alternatives. Installing both puts two extension modules in one process, so yamc.Material and yani.Material are distinct types and the nuclear-data configuration (cross_section_data, the four transmutation_* sources) exists twice, once per package.

Pick yamc when the neutron spectrum should come from a transport solve; pick yani when you have a spectrum already and want none of the transport stack.

What it does not do

• Fixed-source transport only. No criticality or eigenvalue calculations.
• One transmutation stepper (ForwardEulerStepper, beginning-of-step rates). No predictor-corrector.
• Nuclear-data uncertainty reaches transmutation results only. simulate_transmutation(method="independent", data_uncertainty=...) gives a standard deviation on inventories, activity and decay heat from the tallied rates' statistics, MF=33 cross sections and the decay data. The flux is transported once, so it does not respond to a perturbed cross section, and the coupled method does not take data_uncertainty. Transport tallies carry their Monte Carlo error only.
• Pathways are reported per product (get_production_routes), but there is no automatic pathway search across the whole inventory.