2. Depletion Chain – chain.xml

A depletion chain file has a <depletion_chain> root element with one or more <nuclide> child elements. The decay, reaction, and fission product data for each nuclide appears as child elements of <nuclide>.

2.1. <nuclide> Element

The <nuclide> element contains information on the decay modes, reactions, and fission product yields for a given nuclide in the depletion chain. This element may have the following attributes:

name:

Name of the nuclide

half_life:

Half-life of the nuclide in [s]

decay_modes:

Number of decay modes present

decay_energy:

Decay energy released in [eV]

reactions:

Number of reactions present

For each decay mode, a <decay> Element appears as a child of <nuclide>. For each reaction present, a <source> Element appears as a child of <nuclide>. If the nuclide is fissionable, a <neutron_fission_yields> Element appears as well.

2.2. <decay> Element

The <decay> element represents a single decay mode and has the following attributes:

type:

The type of the decay, e.g. ‘ec/beta+’

target:

The daughter nuclide produced from the decay

branching_ratio:

The branching ratio for this decay mode

2.3. <source> Element

The <source> element represents photon and electron sources associated with the decay of a nuclide and contains information to construct an openmc.stats.Univariate object that represents this emission as an energy distribution. This element has the following attributes:

type:

The type of openmc.stats.Univariate source term.

particle:

The type of particle emitted, e.g., ‘photon’ or ‘electron’

parameters:

The parameters of the source term, e.g., for a openmc.stats.Discrete source, the energies (in [eV]) at which the particles are emitted and their relative intensities in [Bq/atom] (in other words, decay constants).

2.4. <reaction> Element

The <reaction> element represents a single transmutation reaction. This element has the following attributes:

type:

The type of the reaction, e.g., ‘(n,gamma)’

Q:

The Q value of the reaction in [eV]

target:

The nuclide produced in the reaction (absent if the type is ‘fission’)

branching_ratio:

The branching ratio for the reaction

2.5. <neutron_fission_yields> Element

The <neutron_fission_yields> element provides yields of fission products for fissionable nuclides. Normally, it has the follow sub-elements:

energies:

Energies in [eV] at which yields for products are tabulated

fission_yields:

Fission product yields for a single energy point. This element itself has a number of attributes/sub-elements:

energy:

Energy in [eV] at which yields are tabulated

products:

Names of fission products

data:

Independent yields for each fission product

In the event that a nuclide doesn’t have any known fission product yields, it is possible to have that nuclide borrow yields from another nuclide by indicating the other nuclide in a single parent attribute. For example:

<neutron_fission_yields parent="U235"/>