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2.6 TWOTRAN ; Two-dimensional S N Transport Calculation
This section describes the input requirements of the two-dimensional S N routine TWOTRAN
required when IC2=3 or IC12=3 is specified in Sect.2.2. This code can be used either in cell
calculation or core calculation. In the SRAC, the original TWOTRAN 5) is split into two steps. In the
first step reading the input and their check and storage into the arrays are executed. In the second step,
the iterative procedure to obtain spectrum is executed. If IC2=3 is specified, the calculation is divided
into the fast energy range and the thermal energy range with the fixed source fed by the SRAC. When
IC12=3 is specified, the whole energy calculation with or without the external fixed source is executed.
However, note that the external source is read in the second step. Therefore input data for the external
source have to be given at the last of all input for a case.
Some functions permitted in the original TWOTRAN are suppressed in the SRAC. As the
macroscopic cross-sections are provided by the SRAC before executing the second step, the control
integers relating to the cross-sections are internally set. As there is no essential change from the
original TWOTRAN, see the references 5) of the TWOTRAN for details.
The input format of the original TWOTRAN is replaced by the free format of SRAC described
in Sect.2.1, however, the original array names and their orders are still kept to facilitate the reference
to the original manual.
Block-1 /1/
NTITLE Number of comment cards
Block-2
TITLE
Job title or job description.
(NTITLE)*/A72/
Block-3 Control integers /42/
1 ITH Type of flux calculation to be performed
= 0 Forward solution
= 1 Adjoint solution
2 ISCT Order of scattering calculation.
There are NM=(ISCT+1)(ISCT+2)/2 spherical harmonic scattering source
components computed. There are not used to compute a scattering source unless
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