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OpenMC/docs/source/io_formats/nuclear_data.rst
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.. _io_nuclear_data:
=========================
Nuclear Data File Formats
=========================
---------------------
Incident Neutron Data
---------------------
**/**
:Attributes: - **filetype** (*char[]*) -- String indicating the type of file
- **version** (*int[2]*) -- Major and minor version of the data
**/<nuclide name>/**
:Attributes: - **Z** (*int*) -- Atomic number
- **A** (*int*) -- Mass number. For a natural element, A=0 is given.
- **metastable** (*int*) -- Metastable state (0=ground, 1=first
excited, etc.)
- **atomic_weight_ratio** (*double*) -- Mass in units of neutron masses
- **n_reaction** (*int*) -- Number of reactions
:Datasets:
- **energy** (*double[]*) -- Energies in [eV] at which cross sections
are tabulated
**/<nuclide name>/kTs/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Datasets:
- **<TTT>K** (*double*) -- kT values in [eV] for each temperature
TTT (in Kelvin)
**/<nuclide name>/reactions/reaction_<mt>/**
:Attributes: - **mt** (*int*) -- ENDF MT reaction number
- **label** (*char[]*) -- Name of the reaction
- **Q_value** (*double*) -- Q value in eV
- **center_of_mass** (*int*) -- Whether the reference frame for
scattering is center-of-mass (1) or laboratory (0)
- **n_product** (*int*) -- Number of reaction products
- **redundant** (*int*) -- Whether reaction is redundant
**/<nuclide name>/reactions/reaction_<mt>/<TTT>K/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Datasets:
- **xs** (*double[]*) -- Cross section values tabulated against the
nuclide energy grid for temperature TTT (in Kelvin)
:Attributes:
- **threshold_idx** (*int*) -- Index on the energy
grid that the reaction threshold corresponds to for
temperature TTT (in Kelvin)
**/<nuclide name>/reactions/reaction_<mt>/product_<j>/**
Reaction product data is described in :ref:`product`.
**/<nuclide name>/urr/<TTT>K/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Attributes: - **interpolation** (*int*) -- interpolation scheme
- **inelastic** (*int*) -- flag indicating inelastic scattering
- **other_absorb** (*int*) -- flag indicating other absorption
- **factors** (*int*) -- flag indicating whether tables are
absolute or multipliers
:Datasets: - **energy** (*double[]*) -- Energy at which probability tables exist
- **table** (*double[][][]*) -- Probability tables
**/<nuclide name>/total_nu/**
This special product is used to define the total number of neutrons produced
from fission. It is formatted as a reaction product, described in
:ref:`product`.
**/<nuclide name>/fission_energy_release/**
:Datasets: - **fragments** (:ref:`function <1d_functions>`) -- Energy
released in the form of fragments as a function of incident
neutron energy.
- **prompt_neutrons** (:ref:`function <1d_functions>`) -- Energy
released in the form of prompt neutrons as a function of incident
neutron energy.
- **delayed_neutrons** (:ref:`function <1d_functions>`) -- Energy
released in the form of delayed neutrons as a function of incident
neutron energy.
- **prompt_photons** (:ref:`function <1d_functions>`) -- Energy
released in the form of prompt photons as a function of incident
neutron energy.
- **delayed_photons** (:ref:`function <1d_functions>`) -- Energy
released in the form of delayed photons as a function of incident
neutron energy.
- **betas** (:ref:`function <1d_functions>`) -- Energy released in
the form of betas as a function of incident neutron energy.
- **neutrinos** (:ref:`function <1d_functions>`) -- Energy released
in the form of neutrinos as a function of incident neutron energy.
- **q_prompt** (:ref:`function <1d_functions>`) -- The prompt fission
Q-value (fragments + prompt neutrons + prompt photons - incident
energy)
- **q_recoverable** (:ref:`function <1d_functions>`) -- The
recoverable fission Q-value (Q_prompt + delayed neutrons + delayed
photons + betas)
--------------------
Incident Photon Data
--------------------
**/**
:Attributes: - **filetype** (*char[]*) -- String indicating the type of file
- **version** (*int[2]*) -- Major and minor version of the data
**/<element>/**
:Attributes: - **Z** (*int*) -- Atomic number
:Datasets:
- **energy** (*double[]*) -- Energies in [eV] at which cross sections
are tabulated
**/<element>/bremsstrahlung/**
:Attributes: - **I** (*double*) -- Mean excitation energy in [eV]
:Datasets: - **electron_energy** (*double[]*) -- Incident electron energy in [eV]
- **photon_energy** (*double[]*) -- Outgoing photon energy as
fraction of incident electron energy
- **dcs** (*double[][]*) -- Bremsstrahlung differential cross section
at each incident energy in [mb/eV]
- **ionization_energy** (*double[]*) -- Ionization potential of each
subshell in [eV]
- **num_electrons** (*int[]*) -- Number of electrons per subshell,
with conduction electrons indicated by a negative value
**/<element>/coherent/**
:Datasets: - **xs** (*double[]*) -- Coherent scattering cross section in [b]
- **integrated_scattering_factor** (:ref:`tabulated <1d_tabulated>`)
-- Integrated coherent scattering form factor
- **anomalous_real** (:ref:`tabulated <1d_tabulated>`) -- Real part
of the anomalous scattering factor
- **anomalous_imag** (:ref:`tabulated <1d_tabulated>`) -- Imaginary
part of the anomalous scattering factor
**/<element>/compton_profiles/**
:Datasets: - **binding_energy** (*double[]*) -- Binding energy for each subshell in [eV]
- **num_electrons** (*double[]*) -- Number of electrons in each subshell
- **pz** (*double[]*) -- Projection of the electron momentum on the
scattering vector in units of :math:`me^2 / \hbar` where :math:`m`
is the electron rest mass and :math:`e` is the electron charge
- **J** (*double[][]*) -- Compton profile for each subshell in units
of :math:`\hbar / (me^2)`
**/<element>/heating/**
:Datasets: - **xs** (*double[]*) -- Total heating cross section in [b-eV]
**/<element>/incoherent/**
:Datasets: - **xs** (*double[]*) -- Incoherent scattering cross section in [b]
- **scattering_factor** (:ref:`tabulated <1d_tabulated>`) --
**/<element>/pair_production_electron/**
:Datasets: - **xs** (*double[]*) -- Pair production (electron field) cross section in [b]
**/<element>/pair_production_nuclear/**
:Datasets: - **xs** (*double[]*) -- Pair production (nuclear field) cross section in [b]
**/<element>/photoelectric/**
:Datasets: - **xs** (*double[]*) -- Total photoionization cross section in [b]
**/<element>/subshells/**
:Attributes: - **designators** (*char[][]*) -- Designator for each shell, e.g. 'M2'
**/<element>/subshells/<designator>/**
:Attributes: - **binding_energy** (*double*) -- Binding energy of the subshell in [eV]
- **num_electrons** (*double*) -- Number of electrons in the subshell
:Datasets: - **transitions** (*double[][]*) -- Atomic relaxation data
- **xs** (*double[]*) -- Photoionization cross section for subshell
in [b] tabulated against the main energy grid
:Attributes:
- **threshold_idx** (*int*) -- Index on the energy
grid of the reaction threshold
-------------------------------
Thermal Neutron Scattering Data
-------------------------------
**/**
:Attributes:
- **version** (*int[2]*) -- Major and minor version of the data
**/<thermal name>/**
:Attributes: - **atomic_weight_ratio** (*double*) -- Mass in units of neutron masses
- **energy_max** (*double*) -- Maximum energy in [eV]
- **nuclides** (*char[][]*) -- Names of nuclides for which the
thermal scattering data applies to
**/<thermal name>/kTs/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Datasets:
- **<TTT>K** (*double*) -- kT values (in eV) for each temperature
TTT (in Kelvin)
**/<thermal name>/elastic/<TTT>K/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Datasets:
- **xs** (:ref:`function <1d_functions>`) -- Thermal elastic
scattering cross section for temperature TTT (in Kelvin)
:Groups:
- **distribution** -- Format for angle-energy distributions are
detailed in :ref:`angle_energy`.
**/<thermal name>/inelastic/<TTT>K/**
<TTT>K is the temperature in Kelvin, rounded to the nearest integer, of the
temperature-dependent data set. For example, the data set corresponding to
300 Kelvin would be located at `300K`.
:Datasets:
- **xs** (:ref:`function <1d_functions>`) -- Thermal inelastic
scattering cross section for temperature TTT (in Kelvin)
:Groups:
- **distribution** -- Format for angle-energy distributions are
detailed in :ref:`angle_energy`.
.. _product:
-----------------
Reaction Products
-----------------
:Object type: Group
:Attributes: - **particle** (*char[]*) -- Type of particle
- **emission_mode** (*char[]*) -- Emission mode (prompt, delayed,
total)
- **decay_rate** (*double*) -- Rate of decay in inverse seconds
- **n_distribution** (*int*) -- Number of angle/energy
distributions
:Datasets:
- **yield** (:ref:`function <1d_functions>`) -- Energy-dependent
yield of the product.
:Groups:
- **distribution_<k>** -- Formats for angle-energy distributions are
detailed in :ref:`angle_energy`. When multiple angle-energy
distributions occur, one dataset also may appear for each
distribution:
:Datasets:
- **applicability** (:ref:`function <1d_functions>`) --
Probability of selecting this distribution as a function
of incident energy
.. _1d_functions:
-------------------------
One-dimensional Functions
-------------------------
Scalar
------
:Object type: Dataset
:Datatype: *double*
:Attributes: - **type** (*char[]*) -- 'constant'
.. _1d_tabulated:
Tabulated
---------
:Object type: Dataset
:Datatype: *double[2][]*
:Description: x-values are listed first followed by corresponding y-values
:Attributes: - **type** (*char[]*) -- 'Tabulated1D'
- **breakpoints** (*int[]*) -- Region breakpoints
- **interpolation** (*int[]*) -- Region interpolation codes
.. _1d_polynomial:
Polynomial
----------
:Object type: Dataset
:Datatype: *double[]*
:Description: Polynomial coefficients listed in order of increasing power
:Attributes: - **type** (*char[]*) -- 'Polynomial'
Coherent elastic scattering
---------------------------
:Object type: Dataset
:Datatype: *double[2][]*
:Description: The first row lists Bragg edges and the second row lists structure
factor cumulative sums.
:Attributes: - **type** (*char[]*) -- 'CoherentElastic'
Incoherent elastic scattering
-----------------------------
:Object type: Dataset
:Datatype: *double[2]*
:Description: The first value is the characteristic bound cross section in [b]
and the second value is the Debye-Waller integral in
[eV\ :math:`^{-1}`].
:Attributes: - **type** (*char[]*) -- 'IncoherentElastic'
.. _angle_energy:
--------------------------
Angle-Energy Distributions
--------------------------
Uncorrelated Angle-Energy
-------------------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'uncorrelated'
:Datasets: - **angle/energy** (*double[]*) -- energies at which angle distributions exist
- **angle/mu** (*double[3][]*) -- tabulated angular distributions for
each energy. The first row gives :math:`\mu` values, the second row
gives the probability density, and the third row gives the
cumulative distribution.
:Attributes: - **offsets** (*int[]*) -- indices indicating where
each angular distribution starts
- **interpolation** (*int[]*) -- interpolation code
for each angular distribution
:Groups: - **energy/** (:ref:`energy distribution <energy_distribution>`)
.. _correlated_angle_energy:
Correlated Angle-Energy
-----------------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'correlated'
:Datasets: - **energy** (*double[]*) -- Incoming energies at which distributions exist
:Attributes:
- **interpolation** (*double[2][]*) -- Breakpoints and
interpolation codes for incoming energy regions
- **energy_out** (*double[5][]*) -- Distribution of outgoing energies
corresponding to each incoming energy. The distributions are
flattened into a single array; the start of a given distribution
can be determined using the ``offsets`` attribute. The first row
gives outgoing energies, the second row gives the probability
density, the third row gives the cumulative distribution, the
fourth row gives interpolation codes for angular distributions, and
the fifth row gives offsets for angular distributions.
:Attributes: - **offsets** (*double[]*) -- Offset for each
distribution
- **interpolation** (*int[]*) -- Interpolation code
for each distribution
- **n_discrete_lines** (*int[]*) -- Number of discrete
lines in each distribution
- **mu** (*double[3][]*) -- Distribution of angular cosines
corresponding to each pair of incoming and outgoing energies. The
distributions are flattened into a single array; the start of a
given distribution can be determined using offsets in the fifth row
of the ``energy_out`` dataset. The first row gives angular cosines,
the second row gives the probability density, and the third row
gives the cumulative distribution.
Kalbach-Mann
------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'kalbach-mann'
:Datasets: - **energy** (*double[]*) -- Incoming energies at which distributions exist
:Attributes:
- **interpolation** (*double[2][]*) -- Breakpoints and
interpolation codes for incoming energy regions
- **distribution** (*double[5][]*) -- Distribution of outgoing
energies and angles corresponding to each incoming energy. The
distributions are flattened into a single array; the start of a
given distribution can be determined using the ``offsets``
attribute. The first row gives outgoing energies, the second row
gives the probability density, the third row gives the cumulative
distribution, the fourth row gives Kalbach-Mann precompound
factors, and the fifth row gives Kalbach-Mann angular distribution
slopes.
:Attributes: - **offsets** (*double[]*) -- Offset for each
distribution
- **interpolation** (*int[]*) -- Interpolation code
for each distribution
- **n_discrete_lines** (*int[]*) -- Number of discrete
lines in each distribution
N-Body Phase Space
------------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'nbody'
- **total_mass** (*double*) -- Total mass of product particles
- **n_particles** (*int*) -- Number of product particles
- **atomic_weight_ratio** (*double*) -- Atomic weight ratio of the
target nuclide in neutron masses
- **q_value** (*double*) -- Q value for the reaction in eV
Coherent Elastic
----------------
This angle-energy distribution is used specifically for coherent elastic thermal
neutron scattering.
:Object type: Group
:Attributes: - **type** (*char[]*) -- "coherent_elastic"
:Hard link: - **xs** -- Link to the coherent elastic scattering cross section
Incoherent Elastic
------------------
This angle-energy distribution is used specifically for incoherent elastic
thermal neutron scattering (derived from an ENDF file directly).
:Object type: Group
:Attributes: - **type** (*char[]*) -- "incoherent_elastic"
:Datasets:
- **debye_waller** (*double*) -- Debye-Waller integral in
[eV\ :math:`^{-1}`]
Incoherent Elastic (Discrete)
-----------------------------
This angle-energy distribution is used for discretized incoherent elastic
thermal neutron scattering distributions that are present in ACE files.
:Object type: Group
:Attributes: - **type** (*char[]*) -- "incoherent_elastic_discrete"
:Datasets:
- **mu_out** (*double[][]*) -- Equiprobable discrete outgoing
angles for each incident neutron energy tabulated
Incoherent Inelastic
--------------------
This angle-energy distribution is used specifically for (continuous) incoherent
inelastic thermal neutron scattering.
:Object type: Group
:Attributes: - **type** (*char[]*) -- "incoherent_inelastic"
:Datasets: The datasets for this angle-energy distribution are the same as for
:ref:`correlated angle-energy distributions
<correlated_angle_energy>`.
Incoherent Inelastic (Discrete)
-------------------------------
This angle-energy distribution is used specifically for incoherent inelastic
thermal neutron scattering where the distributions have been discretized into
equiprobable bins.
:Object type: Group
:Attributes: - **type** (*char[]*) -- "incoherent_inelastic_discrete"
:Datasets: - **energy_out** (*double[][]*) -- Distribution of outgoing
energies for each incoming energy.
- **mu_out** (*double[][][]*) -- Distribution of scattering cosines
for each pair of incoming and outgoing energies.
- **skewed** (*int8_t*) -- Whether discrete angles are equi-probable
(0) or have a skewed distribution (1).
.. _energy_distribution:
--------------------
Energy Distributions
--------------------
Maxwell
-------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'maxwell'
- **u** (*double*) -- Restriction energy in eV
:Datasets:
- **theta** (:ref:`tabulated <1d_tabulated>`) -- Maxwellian
temperature as a function of energy
Evaporation
-----------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'evaporation'
- **u** (*double*) -- Restriction energy in eV
:Datasets:
- **theta** (:ref:`tabulated <1d_tabulated>`) -- Evaporation
temperature as a function of energy
Watt Fission Spectrum
---------------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'watt'
- **u** (*double*) -- Restriction energy in eV
:Datasets: - **a** (:ref:`tabulated <1d_tabulated>`) -- Watt parameter :math:`a`
as a function of incident energy
- **b** (:ref:`tabulated <1d_tabulated>`) -- Watt parameter :math:`b`
as a function of incident energy
Madland-Nix
-----------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'watt'
- **efl** (*double*) -- Average energy of light fragment in eV
- **efh** (*double*) -- Average energy of heavy fragment in eV
Discrete Photon
---------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'discrete_photon'
- **primary_flag** (*int*) -- Whether photon is a primary
- **energy** (*double*) -- Photon energy in eV
- **atomic_weight_ratio** (*double*) -- Atomic weight ratio of
target nuclide in neutron masses
Level Inelastic
---------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'level'
- **threshold** (*double*) -- Energy threshold in the laboratory
system in eV
- **mass_ratio** (*double*) -- :math:`(A/(A + 1))^2`
Continuous Tabular
------------------
:Object type: Group
:Attributes: - **type** (*char[]*) -- 'continuous'
:Datasets: - **energy** (*double[]*) -- Incoming energies at which distributions exist
:Attributes:
- **interpolation** (*double[2][]*) -- Breakpoints and
interpolation codes for incoming energy regions
- **distribution** (*double[3][]*) -- Distribution of outgoing
energies corresponding to each incoming energy. The distributions
are flattened into a single array; the start of a given
distribution can be determined using the ``offsets`` attribute. The
first row gives outgoing energies, the second row gives the
probability density, and the third row gives the cumulative
distribution.
:Attributes: - **offsets** (*double[]*) -- Offset for each
distribution
- **interpolation** (*int[]*) -- Interpolation code
for each distribution
- **n_discrete_lines** (*int[]*) -- Number of discrete
lines in each distribution
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