5. Fission Energy Release File FormatΒΆ

This file is a compact HDF5 representation of the ENDF MT=1, MF=458 data (see ENDF-102 for details). It gives the information needed to compute the energy carried away from fission reactions by each reaction product (e.g. fragment nuclei, neutrons) which depends on the incident neutron energy. OpenMC is distributed with one of these files under data/fission_Q_data_endfb71.h5. More files of this format can be created from ENDF files with the openmc.data.write_compact_458_library function. They can be read with the openmc.data.FissionEnergyRelease.from_compact_hdf5 class method.

Attributes:
  • comment (char[]) – An optional text comment
  • component order (char[][]) – An array of strings specifying the order each reaction product occurs in the data arrays. The components use the 2-3 letter abbreviations specified in ENDF-102 e.g. EFR for fission fragments and ENP for prompt neutrons.
/<nuclide name>/
Nuclides are named by concatenating their atomic symbol and mass number. For example, ‘U235’ or ‘Pu239’. Metastable nuclides are appended with an ‘_m’ and their metastable number. For example, ‘Am242_m1’
Datasets:
  • data (double[][][]) – The energy release coefficients. The

    first axis indexes the component type. The second axis specifies values or uncertainties. The third axis indexes the polynomial order. If the data uses the Sher-Beck format, then the last axis will have a length of one and ENDF-102 should be consulted for energy dependence. Otherwise, the data uses the Madland format which is a polynomial of incident energy.

    For example, if ‘EFR’ is given first in the component order attribute and the data uses the Madland format, then the energy released in the form of fission fragments at an incident energy \(E\) is given by

    \[\text{data}[0, 0, 0] + \text{data}[0, 0, 1] \cdot E + \text{data}[0, 0, 2] \cdot E^2 + \ldots\]

    And its uncertainty is

    \[\text{data}[0, 1, 0] + \text{data}[0, 1, 1] \cdot E + \text{data}[0, 1, 2] \cdot E^2 + \ldots\]