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Setting up GROUPR runs can be daunting, because it has many possibilities
for giving the user complete control over which reactions and data types
are processed. However, for many applications, the user can use
automatic modes that greatly simplify the input. Here is a simple
example of a deck that computes infinitely dilute cross sections for
carbon using a built-in group structure and weight function.
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groupr
20 21 0 22 / ENDF on tape20, PENDF on tape21, GENDF on tape22
1306 3 3 3 3 1 1 1 / 30 groups, CLAW weight, P3
'carbon from ENDF/B-V'/
300 / one temperature
1.e10 / infinite dilution only
3/ process all cross sections on PENDF
6/ process all matrices
16/ process all photon production reactions
0/ end of this temperature
0/ end of groupr input
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A clearer understanding of this input lines can be obtained by studying
the GROUPR input specifications in the online version, a printed NJOY
manual, or the files in the NJOY distribution. The notes after the
"slash" terminator explain most of the features of this input deck.
Because not all user need all possible reactions, the automatic input
process skips over thermal data (MT=221--250) and delayed neutron data
(MT=455). If you need thermal data to be group averaged, include
something like this in your deck:
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3/ all reactions but thermal
3 229 'graphite inelastic'/
3 230 'graphite elastic'/
6/ all matrices but thermal
6 229 'graphite inelastic'/
6 230 'graphite elastic'/
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Similarly, if you need delayed-neutron production and spectra, include
something like this in your deck:
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3 455/ delayed nubar
5 455/ delayed spectra
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The code will automatically provide spectra for all the six time groups
of delayed neutrons. As discussed in the previous subsection, it is
the responsibility of a subsequent code to merge the delayed neutron
data with the prompt data for the calculation of a proper fission source.
As a final example, to obtain self-shielded cross sections and scattering
matrices, you have to ask for several temperatures and several
σ0 values. It is not necessary
to reprocess all the reactions at the higher temperatures; just include
the reactions that occur at resonance energies:
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groupr
20 21 0 22
1050 3 0 3 3 2 3 1
'94-pu-238 from ENDF/B-IV'/
300 900
1e10 1e4 1000 100 10 1
3/ all reactions at 300K
6/ all matrices at 300K
0/ end of first temperature (300K)
3 1 'total'/ only resonance reactions at 900K
3 2 'elastic'/
3 18 'fission'/
3 102 'capture'/
6 2 'elastic'/ yes, you can self shield the elastic matrix
0/ end of second temperature (900K)
0/ end of groupr deck
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GROUPR has other capabilities, including custom group structures, custom
weight functions, the flux calculator, charged particle transfer
matrices, and activation cross section processing, that can be explored
in the detailed documentation
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