CCCC Formats

The CCCC module contains a number of classes for reading various cross section, flux, geometry, and data files with specifications given by the Committee for Computer Code Coordination. The following types of files can be read using classes from this module: ISOTXS, DLAYXS, BRKOXS, RTFLUX, ATFLUX, RZFLUX, MATXS, and SPECTR.

The ISOTXS reader was originally derived from Professor James Holloway’s open-source C++ classes from the University of Michigan and later expanded by Nick Touran for work on his PhD thesis. DLAYXS was later added by Paul Romano. RTFLUX was done by Elliott Biondo.

A description of several CCCC formats are available online for ISOTXS, MATXS, RTFLUX, and RZFLUX. Other format specifications can be found in Los Alamos Report LA-5324-MS.

For a complete specification for the classes in the cccc module, please refer to the Library Reference entry for CCCC Formats – pyne.cccc.

Example Use of Isotxs Class

To load data from an ISOTXS file, one needs to simply initialize an instance of the Isotxs class specifying the path to the ISOTXS file.

In [1]: from pyne import cccc

In [2]: isoFile = cccc.Isotxs('ISOTXS')

In [3]:

After the file has been read, the data from the ISOTXS is now accessible through the attributes of the isoFile object. Some of the attributes are as follows:


Normalized fission spectrum, giving the fraction of neutrons emitted in each energy group.


Maximum energies for each of the energy groups in units of eV.


Minimum energy for the lowest (thermal) energy group, typically somewhere around 0.00001 eV.


Dictionary containing several important parameters. For example isofile.fc['niso'] tells you the number of nuclides in the file and isoFile.fc['ngroup'] tells you the number of energy groups.


Identification label describing the data in the file.


A list of the labels for each nuclide.


A list of nuclides present in the file. Each nuclide is an instance of the Nuclide class which contains data on cross-sections.


Mean neutron velocity in each energy group.