3. Nuclear Data File Formats¶
3.1. 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 Reaction Products.
/<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 Reaction Products.
/<nuclide name>/fission_energy_release/
- Datasets
fragments (function) – Energy released in the form of fragments as a function of incident neutron energy.
prompt_neutrons (function) – Energy released in the form of prompt neutrons as a function of incident neutron energy.
delayed_neutrons (function) – Energy released in the form of delayed neutrons as a function of incident neutron energy.
prompt_photons (function) – Energy released in the form of prompt photons as a function of incident neutron energy.
delayed_photons (function) – Energy released in the form of delayed photons as a function of incident neutron energy.
betas (function) – Energy released in the form of betas as a function of incident neutron energy.
neutrinos (function) – Energy released in the form of neutrinos as a function of incident neutron energy.
q_prompt (function) – The prompt fission Q-value (fragments + prompt neutrons + prompt photons - incident energy)
q_recoverable (function) – The recoverable fission Q-value (Q_prompt + delayed neutrons + delayed photons + betas)
3.2. 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
/<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 \(me^2 / \hbar\) where \(m\) is the electron rest mass and \(e\) is the electron charge
J (double[][]) – Compton profile for each subshell in units of \(\hbar / (me^2)\)
/<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 (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
3.3. 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 (function) – Thermal elastic scattering cross section for temperature TTT (in Kelvin)
- Groups
distribution – Format for angle-energy distributions are detailed in Angle-Energy Distributions.
/<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 (function) – Thermal inelastic scattering cross section for temperature TTT (in Kelvin)
- Groups
distribution – Format for angle-energy distributions are detailed in Angle-Energy Distributions.
3.4. 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 (function) – Energy-dependent yield of the product.
- Groups
distribution_<k> – Formats for angle-energy distributions are detailed in Angle-Energy Distributions. When multiple angle-energy distributions occur, one dataset also may appear for each distribution:
- Datasets
applicability (function) – Probability of selecting this distribution as a function of incident energy
3.5. One-dimensional Functions¶
3.5.1. Scalar¶
- Object type
Dataset
- Datatype
double
- Attributes
type (char[]) – ‘constant’
3.5.2. 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
3.5.3. Polynomial¶
- Object type
Dataset
- Datatype
double[]
- Description
Polynomial coefficients listed in order of increasing power
- Attributes
type (char[]) – ‘Polynomial’
3.5.4. 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’
3.5.5. 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\(^{-1}\)].
- Attributes
type (char[]) – ‘IncoherentElastic’
3.5.6. Sum of functions¶
- Object type
Group
- Attributes
type (char[]) – “Sum”
n (int) – Number of functions
- Datasets
*func_<i> (function) – Dataset for the i-th function (indexing starts at 1)
3.6. Angle-Energy Distributions¶
3.6.3. 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
offsetsattribute. 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
3.6.4. 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
3.6.5. 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
3.6.6. 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\(^{-1}\)]
3.6.7. 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
3.6.8. 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 correlated angle-energy distributions.
3.6.9. 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).
3.6.10. Mixed Elastic¶
This angle-energy distribution is used when an evaluation specifies both coherent and incoherent elastic thermal neutron scattering.
- Object type
Group
- Attributes
type (char[]) – “mixed_elastic”
- Groups
coherent – Distribution for coherent elastic scattering. The format is given in Angle-Energy Distributions.
incoherent – Distribution for incoherent elastic scattering. The format is given in Angle-Energy Distributions.
3.7. Energy Distributions¶
3.7.1. Maxwell¶
- Object type
Group
- Attributes
type (char[]) – ‘maxwell’
u (double) – Restriction energy in eV
- Datasets
theta (tabulated) – Maxwellian temperature as a function of energy
3.7.2. Evaporation¶
- Object type
Group
- Attributes
type (char[]) – ‘evaporation’
u (double) – Restriction energy in eV
- Datasets
theta (tabulated) – Evaporation temperature as a function of energy
3.7.3. Watt Fission Spectrum¶
3.7.4. 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
3.7.5. 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
3.7.6. Level Inelastic¶
- Object type
Group
- Attributes
type (char[]) – ‘level’
threshold (double) – Energy threshold in the laboratory system in eV
mass_ratio (double) – \((A/(A + 1))^2\)
3.7.7. 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
offsetsattribute. 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