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Material

The nuclide inventory being assessed, and its five constructors.

Material 

Material(atoms: Mapping[str, float] | None = None, *, density: float | None = None, volume: float | None = None, name: str = '', decay_data: DecayData | None = None, _specific_activities: Mapping[str, float] | None = None, _atoms_absolute: bool = True)

A nuclide inventory to assess for clearance.

The primary input is a mapping of nuclide name to atom count, which is what an activation or depletion calculation produces:

>>> mat = Material({"Fe56": 8.4e22, "Co60": 1.2e12})

Specific activity in Bq/g is scale invariant, so atom counts, atom densities and atom fractions all give the same answer for the Bq/g limit sets and no density is needed. Volumetric limit sets (Ci/m3) do need one, supplied as density or derived from atom densities.

Warning

The Bq/g denominator is the mass of everything in the mapping, so stable isotopes must be included. Passing only the radioactive nuclides of an activated steel gives a mass thousands of times too small and a specific activity thousands of times too high.

Parameters:

  • atoms

    (Mapping[str, float] | None, default: None ) –

    Nuclide name to atom count. Names may be spelled in any form normalise accepts.

  • density

    (float | None, default: None ) –

    Mass density in g/cm3. Only needed for volumetric limit sets.

  • volume

    (float | None, default: None ) –

    Volume in cm3. Only needed for total activity in Bq or Ci.

  • name

    (str, default: '' ) –

    A label carried through to results, for reporting.

  • decay_data

    (DecayData | None, default: None ) –

    Half-life and mass tables. Defaults to the vendored ENDF/B-VIII.0 and AME2020 values.

Methods:

Attributes:

nuclides property 

nuclides: tuple[str, ...]

The nuclides present, in canonical form, sorted.

atoms property 

atoms: dict[str, float]

Atom amounts as supplied, keyed by canonical name.

mass property 

mass: float

Total mass in grams.

Raises:

  • InsufficientDataError –

    If the material carries only relative amounts, such as atom densities or mass fractions, with no volume to scale them by.

density property 

density: float

Mass density in g/cm3.

Raises:

  • InsufficientDataError –

    If no density was supplied and none can be derived, naming what to pass.

from_atom_counts classmethod 

from_atom_counts(atoms: Mapping[str, float], *, density: float | None = None, volume: float | None = None, **kwargs) -> 'Material'

Build from absolute atom counts. Identical to the constructor.

from_atom_densities classmethod 

from_atom_densities(densities: Mapping[str, float], *, volume: float | None = None, density: float | None = None, **kwargs) -> 'Material'

Build from atom densities in atoms per barn-cm, OpenMC's unit.

The mass density follows from the atom densities and the atomic masses, so no density argument is accepted or needed: supplying one could only contradict the inventory.

Parameters:

  • densities

    (Mapping[str, float]) –

    Nuclide name to atoms/barn-cm.

  • volume

    (float | None, default: None ) –

    Volume in cm3, only needed for total activity.

  • density

    (float | None, default: None ) –

    Not accepted. Present only so that passing it raises rather than being swallowed and ignored.

Raises:

from_masses classmethod 

from_masses(masses: Mapping[str, float], *, density: float | None = None, **kwargs) -> 'Material'

Build from a mass in grams per nuclide.

Parameters:

  • masses

    (Mapping[str, float]) –

    Nuclide name to mass in grams.

  • density

    (float | None, default: None ) –

    Mass density in g/cm3, only needed for volumetric sets.

from_mass_fractions classmethod 

from_mass_fractions(fractions: Mapping[str, float], *, density: float | None = None, **kwargs) -> 'Material'

Build from mass fractions, which need not sum to one.

Parameters:

  • fractions

    (Mapping[str, float]) –

    Nuclide name to mass fraction or weight percent.

  • density

    (float | None, default: None ) –

    Mass density in g/cm3, only needed for volumetric sets.

from_specific_activities classmethod 

from_specific_activities(activities: Mapping[str, float], *, density: float | None = None, **kwargs) -> 'Material'

Build from specific activities in Bq/g, as an assay reports them.

No half-life or atomic mass data is used, since the specific activity is the direct input to the index. Volumetric limit sets then need an explicit density, because activity alone does not imply a mass.

Parameters:

  • activities

    (Mapping[str, float]) –

    Nuclide name to specific activity in Bq/g.

  • density

    (float | None, default: None ) –

    Mass density in g/cm3, only needed for volumetric sets.

specific_activity 

specific_activity(by_nuclide: bool = False) -> 'float | dict[str, float]'

Specific activity in Bq/g.

Scale invariant, so this works from atom counts, atom densities or atom fractions alike.

Parameters:

  • by_nuclide

    (bool, default: False ) –

    Return a dict keyed by nuclide rather than the total.

Returns:

  • 'float | dict[str, float]' –

    Bq/g as a float, or a dict of them.

activity 

activity(units: str = 'Bq/g', by_nuclide: bool = False) -> 'float | dict[str, float]'

Activity in the requested units.

Parameters:

  • units

    (str, default: 'Bq/g' ) –

    One of ACTIVITY_UNITS.

  • by_nuclide

    (bool, default: False ) –

    Return a dict keyed by nuclide rather than the total.

Returns:

  • 'float | dict[str, float]' –

    The activity as a float, or a dict of them.

Raises:

  • ValueError –

    If the units are not recognised.

  • InsufficientDataError –

    If the units need a density or volume the material does not have.