YANI

Yet Another Nuclide Inventory. A material, an irradiation schedule and a neutron spectrum in; inventories, activities, decay heat, contact dose and decay photon spectra out.

Try it online 🌐 | Documentation 📝 | PyPI 🐍

The browser version needs no install and no account. It is the same Rust solver compiled to WebAssembly, against the same continuous-energy data, so it answers what the wheel answers rather than a reduced version of it. The solve runs on your machine; nothing is uploaded.

pip install yani

import yani

# flexible use of different libraries
yani.cross_section_data = "tendl-2025"
yani.transmutation_reactions = "tendl-2025"
yani.transmutation_branch_ratios = "tendl-2025"
yani.transmutation_decay_data = "endf-b8.1"
yani.transmutation_fission_yields = "endf-b8.1"

# make your own or use inbuilt material definitions
steel = yani.materials.pnnl.material(key="Steel, Stainless 316", volume=1000.0)

# define the neutron spectrum
spectrum = yani.NeutronSource(
    energy=yani.sources.Histogram(
        boundaries=[1e-5, 1e5, 1e6, 1.5e7], probabilities=[1e12, 1e13, 1e14]
    )
)

# define the irradiation and cooling schedule
schedule = yani.PulseSchedule(steps=[
    yani.Pulse(rate=1.11e14, duration=(1, "a"), source=spectrum),
    yani.Cooldown(duration=(1, "d")),
])

# perform the simulation
results = steel.transmute(schedule=schedule)

# access the last material in the time steps (id 0 when the material has none)
final = results.step_materials(material_id=steel.id or 0)[-1]

# convenient access to useful properties of the material
print(final.activity(), "Bq")
print(final.decay_heat(), "W")
print(final.contact_dose(), "Gy/h")

What it solves

The nuclide inventory under irradiation is the Bateman equations with reaction terms, dN/dt = A N, solved as a matrix exponential N(t) = exp(A t) N(0) by CRAM at order 48. The solver is Rust; the wheel needs no compiler and no external toolchain.