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

yani.cross_section_data = "tendl-2025"
yani.transmutation_reactions = "tendl-2025"
yani.transmutation_branch_ratios = "tendl-2025"
yani.transmutation_decay_data = "endf-b8.1"      # TENDL has no decay data
yani.transmutation_fission_yields = "endf-b8.1"  # nor fission yields

steel = yani.materials.pnnl.material(key="Steel, Stainless 316", volume=1000.0)
spectrum = yani.NeutronSource(
    energy=yani.sources.Histogram(
        boundaries=[1e-5, 1e5, 1e6, 1.5e7], probabilities=[1e12, 1e13, 1e14]
    )
)
schedule = yani.PulseSchedule(steps=[
    yani.Pulse(rate=1.11e14, duration=(1, "a"), source=spectrum),
    yani.Cooldown(duration=(1, "d")),
])

results = steel.transmute(schedule=schedule)
final = results.step_materials(material_id=steel.id or 0)[-1]
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.

What this repository contains

Documentation, packaging and release automation. The code lives in the yani-core wheel this package depends on, which provides the yani module itself, its type stubs and its docstrings. pip install yani pulls it in.

That arrangement is why there is no Python here: one source of truth for the API, and no re-export layer that can drift from it.