Keyword:PROBTABLE

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PROBTABLE multxs {0} userpar {1}


This keyword causes the probability tables to be read for the nuclides specified by the elements listed by the SSFCHOOSE keyword.

The self-shielding is applied to the existing cross section value as a multiplicative factor if multxs is set to 1. If it is set to 0, then the cross section values in the energy groups for which there are probability table data are replaced by values which are derived directly from the probability tables.

The second argument defines the way in which the self-shielding factors (SSF) are computed:

usepar = 0 -- use the total cross section to calculate one SSF for each nuclide and apply this factor to all relevant cross sections;
usepar = 1 -- use macro-partial cross sections to calculate a separate SSF for each macro-partial and apply it to relevant reactions contributing to that macro-partial.

If the 616-group infinitely-dilute cross sections in the EAF data library and the CALENDF probability table data were fully consistent, these two methods of calculation would give the same answers. However, the EAF data do not contain the elastic scattering cross sections, and so cannot give the correct total cross section. The CALENDF probability tables do give the correct total cross sections, but only provide cross sections for sets of macro-partials, and so have to use the EAF data to apportion the cross sections when they are used to replace EAF values when self-shielding is included. The replacement option is the recommended one, but both options are included so that the user can assess the uncertainty of the effective collapsed self-shielding factor. An expert mode that allows fine-tuning of the dilution factors is provided using the SSFDILUTION keyword.

See the probability table self-shielding page for a more detailed explanation of the alternative calculations performed and for an illustration of including self-shielding in the computation of the effective collapsed cross section data.

Example usage of macro-partial self-shielding factors applied as a multiplicative factor:

< -- Control phase -- >
...
GETXS 1 709
PROBTABLE 1 1
SSFCHOOSE ... 
...
FISPACT
* Title of the simulation
< -- Initial phase -- > 
...
< -- Inventory phase -- > 
...