Keyword:GETXS

GETXS libxs <ebins>

---

This keyword has two integer parameters. If the first parameter libxs is set to 0, then the second parameter should be omitted, and cross section data are read from the existing collapsed library (collapx file) specified in the files file. If libxs is 1, then the second parameter ebins gives the number of energy bins to be used in collapsing the cross section data from the ENDF library files and fluxes or arb_flux files specified in the files file. If libxs is -1, then the ENDF data are read from the compressed binary version of the ENDF data stored in the file specified by xs_endfb in the files file. Note that the value libxs = -1 is not valid for legacy EAF libraries. For information on the preparation of the compressed binary ENDF data files see this page.

The GETXS keyword may also be used in the initial conditions and inventory calculation phases to modify the cross sections, for example to handle time-dependent projectile spectra and temperature changes in cross-sections.

The number of energy groups ebins must be consistent with the number of groups in the supplied library file. The permitted numbers of groups for cross-section data are, for the most recent public distribution, the CCFE-709 for neutrons and CCFE-162 for charged particles. Legacy EAF libraries and their various group structures may also be used.

Example usage, where the cross sections are re-collapsed every 20 days during some irradiation simulation:

< -- Control phase -- >
...
GETXS 1 709
FISPACT
* Title of the simulation
< -- Initial phase -- > 
...
< -- Inventory phase -- > 
...
TIME 20.0 DAYS
GETXS 1 709
TIME 20.0 DAYS
GETXS 1 709
TIME 20.0 DAYS
GETXS 1 709
...