TEST 8 -- ZPR-6/7 SPH. HETERO MODEL 0 3 0 1 1 1 0 3 0 0 80 2 50 0 0 2 7 50 1 0 CORE BLANKT END 300 .2223 6 2R1.09/ U203 300 .6350 -6/ NA 300 1.270 -6/ FE203 300 .3175 -6/ CLAD 300 .0381 -6/ FUEL 300 .2794 -6/ BLANKT/ 0 1 MONAT 5.0E-5/ 0 1 FE56 4.474E-2/ 0 1 CR52 1.257E-2/ 0 1 NI58 5.479E-3/ 0 1 MN55 1.01E-3/ 0 2 U235 3.36E-5/ 0 2 U238 1.572E-2/ 0 2 016 4.724E-2/ 0 3 NA23 2.235E-2/ 0 4 016 4.724E-2/ 0 4 FE56 3.215E-2/ 0 4 MONAT 6.3E-5/ 0 5 FE56 5.706E-2/ 0 5 CR52 1.639E-2/ 0 5 NI58 8.118E-3/ 0 5 MN55 1.41E-4/ 0 6 PU239 9.8506E-3/ 0 6 PU240 1.308E-3/ 0 6 PU241 1.473E-4/ 0 6 U235 6.17E-5/ 0 6 U238 2.7584E-2/ 0 6 MONAT 2.498E-3/ 1 6 PU239 8.8672E-4 CC/ 1 6 PU240 1.1944E-4 CC/ 1 6 PU241 1.33E-5 CC/ 1 6 U235 7.14E-6 CC/ 1 2 U235 5.46E-6 CC/ 1 6 U238 2.5203E-3 CC/ 1 2 U238 3.2601E-3 CC/ 1 6 MONAT 2.357E-4 CC/ 1 3 NA23 9.290E-3 CC/ 1 4 016 8.947E-3 CC/ 1 2 016 5.033E-3 CC/ 1 5 FE56 1.26E-3 CC/ 1 4 FE56 5.929E-3 CC/ 1 1 FE56 5.778E-3 CC/ 1 5 CR52 4.96E-4 CC/ 1 1 CR52 2.213E-3 CC/ 1 5 NI58 2.27E-4 CC/ 1 1 NI58 1.013E-3 CC/ 1 5 MN55 3.9E-5 CC/ 1 1 MN55 1.73E-4 CC/ 2 7 U235 8.56E-5/ 2 7 U238 3.96179E-2/ 2 7 MONAT 3.8E-6/ 2 7 016 2.4E-5/ 2 7 FE56 4.637E-3/ 2 7 CR52 1.295E-3/ 2 7 NI58 5.635E-4/ 2 7 MN55 9.98E-5/ CHI STOPThis run is similar to problem 7 except that additional regions are defined for the infinite slab model of the core cell. These regions have
IMIX=0 so that their cross-sections are not written
onto the output file. However, the macroscopic cross-section for
each region is calculated and used during the self-shielding
iteration. To compute the Dancoff correction, the code sums up
the optical path to the left from one region containing a
particular material to the next region containing the same
material, and then it does the same thing to the right. In either
case, if the sum gets to the cell edge before the ``black''
region is found, the optical path is doubled to account for the
reflective boundary condition. If the left optical path is zero,
it is set equal to the right path; the complementary procedure is
used if the right optical path vanishes. Therefore, both
symmetric and asymmetric two-region equivalent cells are formed.
It is clear from the way the multiregion cell was constructed
that the homogenized core cross sections cannot be computed by
homogenizing regions 1 through 5 directly. In addition, the
material loadings varied from cell to cell in the actual
assembly; and other structure, instrumentation, and control
regions also contributed to the net densities for the assembly.
TRANSX handles this problem by defining the core mix using the
constituent cross sections from regions 1-5 but using the homogenized
densities from the homogeneous model. When a particular isotope
occurs in several different regions, the homogenized density is
apportioned between them (e.g., 81.7% of the 304 stainless steel
is in region 1, and 18.3% is in region 5 with different
background cross sections). The CC command is used to
request constituent cross sections because these densities are
cell-averaged densities.
The model used in this example accounts for the heterogeneous self-shielding effect, but not for the advantage and disadvantage effects. They can be obtained by using a flux solution by regions to do a flux and volume weighting of each cross section in the assembly. This can be done using two TRANSX runs and an SN code as shown in Sample Problems 10 and 11. These examples also illustrate how to use thermal upscatter cross sections.
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