Shift Reference Model for SEFOR Core I-E

The SEFOR core could accommodate a maximum of 109 hexagon fuel assemblies. A standard fuel assembly contained six fuel rods arranged around a central structure rod and reinforced with six steel side rods. These fuel rods contained ~18.7% fissile plutonium (Pu239 and Pu241) and were held in their positions by a hex sleeve surrounding a central rod. In addition to the Standard fuel Assemblies (SA), several variants were used in SEFOR core configuration I-E, including substitutions for standard fuel rods by Guinea Pig (GP) rods with higher fissile Pu concentration of 25.0% or by B4C rods (AFA). A “Drywell” channel was located at the center of the core, which was mostly empty and housed experimental devices such as the Fast Reactivity Excursion Device (FRED) during transient tests.

Inputs

The input for developing the Shift reference model Core I-E is listed in Listing 1 and Listing 2. The Shift simulation employed 500,000 neutron histories per cycle for a total of 500 cycles, of which 50 cycles were inactive. This calculation conditions produced a standard deviation in k-eff of approximately 4 pcm.

Listing 1: 

' --- SEFOR I-E at 450 K
' --- Author: Donny Hartanto, October 2024
' -----------------------------------------------------------------------------
' - Both axial and radial expansions are considered.
' - Length of the regions in the both Ni axial reflectors and core is expanded
'   according to the linear thermal expansion coefficient in the benchmark.
' - Fuel rod length followed the specification in Table 1. BeO and SS length 
'   followed the spec in Table 2, however the expansion of SS is limited only
'   to the fuel rod region. No SS expansion in Na-steel and Na-grid plate region.
' - Specifically, the radial and axial expansion coefficient is applied to fuel, BeO, 
'    SS, Ni. B4C is only expanded radially.
' - Nuclide density of the expanded region is reduced according to its volume
'   radio reduction to conserve the mass.

=csas6-shift
SEFOR Core I-E at 450 K
ce_v7.1_endf

read comp
' Standard Fuel (18.7%)
 pu-239   1   0.0   4.08031E-03  449.8167  end
 pu-240   1   0.0   3.66406E-04  449.8167  end
  u-235   1   0.0   3.83521E-05  449.8167  end
  u-238   1   0.0   1.73945E-02  449.8167  end
  o-16    1   0.0   4.37142E-02  449.8167  end
' Guinea Pig Fuel (25.0%)
 pu-239   2   0.0   5.45489E-03  449.8167  end
 pu-240   2   0.0   4.89849E-04  449.8167  end
  u-235   2   0.0   3.50453E-05  449.8167  end
  u-238   2   0.0   1.58946E-02  449.8167  end
  o-16    2   0.0   4.36894E-02  449.8167  end
' UO2 insulator
  u-235   3   0.0   4.92079E-05  449.8167  end
  u-238   3   0.0   2.23181E-02  449.8167  end
  o-16    3   0.0   4.47347E-02  449.8167  end
' Coolant at 450 K
 na-23    11  0.0   2.39160E-02  449.8167  end
' SS-316
 cr-50    21  0.0   6.90859E-04  449.8167  end
 cr-52    21  0.0   1.33222E-02  449.8167  end
 cr-53    21  0.0   1.51071E-03  449.8167  end
 cr-54    21  0.0   3.76040E-04  449.8167  end
 fe-54    21  0.0   3.41037E-03  449.8167  end
 fe-56    21  0.0   5.35351E-02  449.8167  end
 fe-57    21  0.0   1.23633E-03  449.8167  end
 fe-58    21  0.0   1.64532E-04  449.8167  end
 mo-100   21  0.0   1.22044E-04  449.8167  end
 mo-92    21  0.0   1.88080E-04  449.8167  end
 mo-94    21  0.0   1.17230E-04  449.8167  end
 mo-95    21  0.0   2.01769E-04  449.8167  end
 mo-96    21  0.0   2.11398E-04  449.8167  end
 mo-97    21  0.0   1.21032E-04  449.8167  end
 mo-98    21  0.0   3.05815E-04  449.8167  end
 ni-58    21  0.0   7.61491E-03  449.8167  end
 ni-60    21  0.0   2.93327E-03  449.8167  end
 ni-61    21  0.0   1.27504E-04  449.8167  end
 ni-62    21  0.0   4.06546E-04  449.8167  end
 ni-64    21  0.0   1.03540E-04  449.8167  end
' SS-304
 cr-50    22  0.0   8.17351E-04  449.8167  end
 cr-52    22  0.0   1.57623E-02  449.8167  end
 cr-53    22  0.0   1.78728E-03  449.8167  end
 cr-54    22  0.0   4.44885E-04  449.8167  end
 fe-54    22  0.0   3.48075E-03  449.8167  end
 fe-56    22  0.0   5.46400E-02  449.8167  end
 fe-57    22  0.0   1.26184E-03  449.8167  end
 fe-58    22  0.0   1.67927E-04  449.8167  end
 ni-58    22  0.0   6.80694E-03  449.8167  end
 ni-60    22  0.0   2.62205E-03  449.8167  end
 ni-61    22  0.0   1.13973E-04  449.8167  end
 ni-62    22  0.0   3.63413E-04  449.8167  end
 ni-64    22  0.0   9.25497E-05  449.8167  end
' SS-304_abs
 cr-50    23  0.0   8.17447E-04  449.8167  end
 cr-52    23  0.0   1.57642E-02  449.8167  end
 cr-53    23  0.0   1.78749E-03  449.8167  end
 cr-54    23  0.0   4.44937E-04  449.8167  end
 fe-54    23  0.0   3.48116E-03  449.8167  end
 fe-56    23  0.0   5.46464E-02  449.8167  end
 fe-57    23  0.0   1.26199E-03  449.8167  end
 fe-58    23  0.0   1.67947E-04  449.8167  end
 ni-58    23  0.0   6.80774E-03  449.8167  end
 ni-60    23  0.0   2.62236E-03  449.8167  end
 ni-61    23  0.0   1.13987E-04  449.8167  end
 ni-62    23  0.0   3.63455E-04  449.8167  end
 ni-64    23  0.0   9.25606E-05  449.8167  end
' SS-304_FRED
 cr-50    24  0.0   8.17596E-04  449.8167  end
 cr-52    24  0.0   1.57670E-02  449.8167  end
 cr-53    24  0.0   1.78782E-03  449.8167  end
 cr-54    24  0.0   4.45018E-04  449.8167  end
 fe-54    24  0.0   3.48180E-03  449.8167  end
 fe-56    24  0.0   5.46564E-02  449.8167  end
 fe-57    24  0.0   1.26222E-03  449.8167  end
 fe-58    24  0.0   1.67978E-04  449.8167  end
 ni-58    24  0.0   6.80898E-03  449.8167  end
 ni-60    24  0.0   2.62284E-03  449.8167  end
 ni-61    24  0.0   1.14008E-04  449.8167  end
 ni-62    24  0.0   3.63522E-04  449.8167  end
 ni-64    24  0.0   9.25775E-05  449.8167  end
' SS-316_FRED
 cr-50    25  0.0   6.91067E-04  449.8167  end
 cr-52    25  0.0   1.33262E-02  449.8167  end
 cr-53    25  0.0   1.51117E-03  449.8167  end
 cr-54    25  0.0   3.76153E-04  449.8167  end
 fe-54    25  0.0   3.41139E-03  449.8167  end
 fe-56    25  0.0   5.35512E-02  449.8167  end
 fe-57    25  0.0   1.23670E-03  449.8167  end
 fe-58    25  0.0   1.64582E-04  449.8167  end
 mo-100   25  0.0   1.22081E-04  449.8167  end
 mo-92    25  0.0   1.88136E-04  449.8167  end
 mo-94    25  0.0   1.17265E-04  449.8167  end
 mo-95    25  0.0   2.01830E-04  449.8167  end
 mo-96    25  0.0   2.11462E-04  449.8167  end
 mo-97    25  0.0   1.21068E-04  449.8167  end
 mo-98    25  0.0   3.05907E-04  449.8167  end
 ni-58    25  0.0   7.61720E-03  449.8167  end
 ni-60    25  0.0   2.93415E-03  449.8167  end
 ni-61    25  0.0   1.27542E-04  449.8167  end
 ni-62    25  0.0   4.06668E-04  449.8167  end
 ni-64    25  0.0   1.03571E-04  449.8167  end
' BeO
 be-beo   26  0.0   6.84143E-02  449.8167  end
  o-16    26  0.0   6.84143E-02  449.8167  end
' B4C
  b-10    27  0.0   1.32047E-02  449.8167  end
  b-11    27  0.0   5.31509E-02  449.8167  end
  c-12    27  0.0   1.65886E-02  449.8167  end
' Ni Axial
 ni-58    28  0.0   5.93541E-02  449.8167  end
 ni-60    28  0.0   2.28635E-02  449.8167  end
 ni-61    28  0.0   9.93799E-04  449.8167  end
 ni-62    28  0.0   3.16883E-03  449.8167  end
 ni-64    28  0.0   8.07005E-04  449.8167  end
' Downcomer Inner Vessel
 na-23    31  0.0   1.48350E-02  449.8167  end
 cr-50    31  0.0   2.34745E-04  449.8167  end
 cr-52    31  0.0   4.52673E-03  449.8167  end
 cr-53    31  0.0   5.13299E-04  449.8167  end
 cr-54    31  0.0   1.27773E-04  449.8167  end
 fe-54    31  0.0   9.99616E-04  449.8167  end
 fe-56    31  0.0   1.56923E-02  449.8167  end
 fe-57    31  0.0   3.62408E-04  449.8167  end
 fe-58    31  0.0   4.82292E-05  449.8167  end
 ni-58    31  0.0   1.95489E-03  449.8167  end
 ni-60    31  0.0   7.53037E-04  449.8167  end
 ni-61    31  0.0   3.27337E-05  449.8167  end
 ni-62    31  0.0   1.04375E-04  449.8167  end
 ni-64    31  0.0   2.65802E-05  449.8167  end
' Downcomer Outer Vessel
 mg-24    32  0.0   4.12309E-04  449.8167  end
 mg-25    32  0.0   5.21977E-05  449.8167  end
 mg-26    32  0.0   5.74694E-05  449.8167  end
 al-27    32  0.0   1.12844E-02  449.8167  end
 cr-50    32  0.0   1.28512E-04  449.8167  end
 cr-52    32  0.0   2.47827E-03  449.8167  end
 cr-53    32  0.0   2.81011E-04  449.8167  end
 cr-54    32  0.0   6.99491E-05  449.8167  end
 fe-54    32  0.0   5.47272E-04  449.8167  end
 fe-56    32  0.0   8.59100E-03  449.8167  end
 fe-57    32  0.0   1.98405E-04  449.8167  end
 fe-58    32  0.0   2.64034E-05  449.8167  end
 ni-58    32  0.0   1.07022E-03  449.8167  end
 ni-60    32  0.0   4.12259E-04  449.8167  end
 ni-61    32  0.0   1.79202E-05  449.8167  end
 ni-62    32  0.0   5.71389E-05  449.8167  end
 ni-64    32  0.0   1.45518E-05  449.8167  end
' Reflector
 mg-24    33  0.0   7.44450E-05  449.8167  end
 mg-25    33  0.0   9.42463E-06  449.8167  end
 mg-26    33  0.0   1.03762E-05  449.8167  end
 al-27    33  0.0   2.03752E-03  449.8167  end
 cr-50    33  0.0   2.77734E-05  449.8167  end
 cr-52    33  0.0   5.35588E-04  449.8167  end
 cr-53    33  0.0   6.07314E-05  449.8167  end
 cr-54    33  0.0   1.51177E-05  449.8167  end
 fe-54    33  0.0   1.18273E-04  449.8167  end
 fe-56    33  0.0   1.85668E-03  449.8167  end
 fe-57    33  0.0   4.28782E-05  449.8167  end
 fe-58    33  0.0   5.70638E-06  449.8167  end
 ni-58    33  0.0   4.99710E-02  449.8167  end
 ni-60    33  0.0   1.92485E-02  449.8167  end
 ni-61    33  0.0   8.36735E-04  449.8167  end
 ni-62    33  0.0   2.66786E-03  449.8167  end
 ni-64    33  0.0   6.79430E-04  449.8167  end
' Radial shield
 mg-24    34  0.0   2.71254E-04  449.8167  end
 mg-25    34  0.0   3.43404E-05  449.8167  end
 mg-26    34  0.0   3.78086E-05  449.8167  end
 cr-50    34  0.0   9.86654E-05  449.8167  end
 cr-52    34  0.0   1.90267E-03  449.8167  end
 cr-53    34  0.0   2.15751E-04  449.8167  end
 cr-54    34  0.0   5.37036E-05  449.8167  end
 fe-54    34  0.0   4.20168E-04  449.8167  end
 fe-56    34  0.0   6.59577E-03  449.8167  end
 fe-57    34  0.0   1.52329E-04  449.8167  end
 fe-58    34  0.0   2.02719E-05  449.8167  end
 ni-58    34  0.0   8.21692E-04  449.8167  end
 ni-60    34  0.0   3.16512E-04  449.8167  end
 ni-61    34  0.0   1.37589E-05  449.8167  end
 ni-62    34  0.0   4.38683E-05  449.8167  end
 ni-64    34  0.0   1.11725E-05  449.8167  end
  b-10    34  0.0   5.40601E-03  449.8167  end
  b-11    34  0.0   2.17599E-02  449.8167  end
  c-12    34  0.0   6.79150E-03  449.8167  end
' Na Grid Plate
 na-23    35  0.0   1.68850E-02  449.8167  end
 cr-50    35  0.0   1.99835E-04  449.8167  end
 cr-52    35  0.0   3.85357E-03  449.8167  end
 cr-53    35  0.0   4.36962E-04  449.8167  end
 cr-54    35  0.0   1.08771E-04  449.8167  end
 fe-54    35  0.0   8.50997E-04  449.8167  end
 fe-56    35  0.0   1.33588E-02  449.8167  end
 fe-57    35  0.0   3.08517E-04  449.8167  end
 fe-58    35  0.0   4.10573E-05  449.8167  end
 ni-58    35  0.0   1.66423E-03  449.8167  end
 ni-60    35  0.0   6.41055E-04  449.8167  end
 ni-61    35  0.0   2.78666E-05  449.8167  end
 ni-62    35  0.0   8.88497E-05  449.8167  end
 ni-64    35  0.0   2.26275E-05  449.8167  end
  b-10    35  0.0   6.60243E-04  449.8167  end
  b-11    35  0.0   2.65754E-03  449.8167  end
  c-12    35  0.0   8.29451E-04  449.8167  end
' Na Steel
 na-23    36  0.0   1.35120E-02  449.8167  end
 cr-50    36  0.0   2.66172E-04  449.8167  end
 cr-52    36  0.0   5.13286E-03  449.8167  end
 cr-53    36  0.0   5.82020E-04  449.8167  end
 cr-54    36  0.0   1.44878E-04  449.8167  end
 fe-54    36  0.0   1.13346E-03  449.8167  end
 fe-56    36  0.0   1.77932E-02  449.8167  end
 fe-57    36  0.0   4.10931E-04  449.8167  end
 fe-58    36  0.0   5.46867E-05  449.8167  end
 ni-58    36  0.0   2.21669E-03  449.8167  end
 ni-60    36  0.0   8.53861E-04  449.8167  end
 ni-61    36  0.0   3.71173E-05  449.8167  end
 ni-62    36  0.0   1.18350E-04  449.8167  end
 ni-64    36  0.0   3.01385E-05  449.8167  end
  b-10    36  0.0   6.60243E-04  449.8167  end
  b-11    36  0.0   2.65754E-03  449.8167  end
  c-12    36  0.0   8.29451E-04  449.8167  end
' Steel void
 cr-50    37  0.0   1.23500E-04  449.8167  end
 cr-52    37  0.0   2.38160E-03  449.8167  end
 cr-53    37  0.0   2.70060E-04  449.8167  end
 cr-54    37  0.0   6.72230E-05  449.8167  end
 fe-54    37  0.0   5.25940E-04  449.8167  end
 fe-56    37  0.0   8.25610E-03  449.8167  end
 fe-57    37  0.0   1.90670E-04  449.8167  end
 fe-58    37  0.0   2.53750E-05  449.8167  end
 ni-58    37  0.0   1.02850E-03  449.8167  end
 ni-60    37  0.0   3.96190E-04  449.8167  end
 ni-61    37  0.0   1.72220E-05  449.8167  end
 ni-62    37  0.0   5.49120E-05  449.8167  end
 ni-64    37  0.0   1.39840E-05  449.8167  end
end comp

read param
 gen=220
 nsk=20
 npg=100000
 htm=no
end param

read geometry
unit 1
  com="Central Pin with tightener"
  cylinder  10  0.98942   41.5320   30.7450  com="Lower Ni Reflector"
  cylinder  20  0.98942  134.4970   41.5320  com="BeO"
  cylinder  30  0.98942  145.2840  134.4970  com="Upper Ni Reflector"
  cylinder  40  1.01239  145.3628  145.2840  com="Na steel to fill the missing region"
  cylinder 100  1.01239  145.3628   30.7450  com="gap"
  cylinder 110  1.11426  145.3628   30.7450  com="SS316 clad"
  hexprism 120  1.22244  145.3628   30.7450  com="Na coolant"
  hexprism 130  1.31158  145.3628   30.7450  com="SS304 Duct"
     media  28  1  10
     media  26  1  20
     media  28  1  30
     media  36  1  40
     media   0  1 100 -40 -30 -20 -10
     media  21  1 110 -100
     media  11  1 120 -110
     media  22  1 130 -120
  boundary 130 

unit 2
  com="Fuel pin with standard fuel"
  cylinder  10  1.11426   41.5320   30.7450  com="Lower Ni Reflector"
  cylinder  20  1.11426   42.4845   41.5320  com="UO2 insulator"
  cylinder  30  1.11426   94.9136   42.4845  com="Pu fuel"
  cylinder  40  1.11426   95.8661   94.9136  com="UO2 insulator"
  cylinder  50  1.11426   99.1481   95.8661  com="Spring (void)"
  cylinder  60  1.11426  100.1006   99.1481  com="UO2 insulator"
  cylinder  70  1.11426  133.6233  100.1006  com="Pu fuel"
  cylinder  80  1.11426  134.5758  133.6233  com="UO2 insulator"
  cylinder  90  1.11426  145.3628  134.5758  com="Upper Ni Reflector"
  cylinder 100  1.13331  145.3628   30.7450  com="gap"
  cylinder 110  1.23518  145.3628   30.7450  com="SS316 clad"
     media  28  1  10
     media   3  1  20
     media   1  1  30
     media   3  1  40
     media   0  1  50
     media   3  1  60
     media   1  1  70
     media   3  1  80
     media  28  1  90
     media   0  1 100 -90 -80 -70 -60 -50
                      -40 -30 -20 -10
     media  21  1 110 -100
  boundary 110    

unit 3
  com="Fuel pin with guinea pig fuel"
  cylinder  10  1.11426   41.5320   30.7450  com="Lower Ni Reflector"
  cylinder  20  1.11426   42.4845   41.5320  com="UO2 insulator"
  cylinder  30  1.11426   94.9136   42.4845  com="Pu fuel"
  cylinder  40  1.11426   95.8661   94.9136  com="UO2 insulator"
  cylinder  50  1.11426   99.1481   95.8661  com="Spring (void)"
  cylinder  60  1.11426  100.1006   99.1481  com="UO2 insulator"
  cylinder  70  1.11426  133.6233  100.1006  com="Pu fuel"
  cylinder  80  1.11426  134.5758  133.6233  com="UO2 insulator"
  cylinder  90  1.11426  145.3628  134.5758  com="Upper Ni Reflector"
  cylinder 100  1.13331  145.3628   30.7450  com="gap"
  cylinder 110  1.23518  145.3628   30.7450  com="SS316 clad"
     media  28  1  10
     media   3  1  20
     media   2  1  30
     media   3  1  40
     media   0  1  50
     media   3  1  60
     media   2  1  70
     media   3  1  80
     media  28  1  90
     media   0  1 100 -90 -80 -70 -60 -50
                      -40 -30 -20 -10
     media  21  1 110 -100
  boundary 110 
      
unit 4
  com="Absorber pin"
  cylinder  10  1.11426   41.5320   30.7450  com="Lower Ni Reflector"
  cylinder  20  0.80133  134.5758   41.5320  com="SS304 central"
  cylinder  30  1.13331  134.4008   41.5320  com="B4C absorber"
  cylinder  40  1.11426  145.3628  134.5758  com="Upper Ni Reflector"
  cylinder 100  1.13331  145.3628   30.7450  com="gap"
  cylinder 110  1.23518  145.3628   30.7450  com="SS316 clad"
     media  28  1  10
     media  23  1  20
     media  27  1  30 -20
     media  28  1  40 -20
     media   0  1 100 -40 -30 -20 -10
     media  21  1 110 -100
  boundary 110 

unit 6
  com="Wire pin"
  cylinder 100  0.31834  145.3628   30.7450  com="wire pin"
     media  22  1 100
  boundary 100 

unit 10
  com="FRED"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
  cylinder  20  1.67444  165.6018   30.7450  com="Absorber for transient, now void"
  cylinder  30  1.75726  165.6018   30.7450  com="Gap"
  cylinder  40  2.11381  165.6018   30.7450  com="SS316 clad" 
 rhexprism  50  3.85834  165.6018   30.7450  com="Steel duct" 
 rhexprism  60  4.01114  165.6018   30.7450  com="Inside duct"
 rhexprism  70  4.02388  165.6018   30.7450  com="Sodium gap"
 rhexprism 100  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media   0  1  20
     media   0  1  30 -20
     media  25  1  40 -30
     media   0  1  50 -40
     media  24  1  60 -50
     media  11  1  70 -60
  boundary 100

unit 11
  com="Standard fuel assembly"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 12
  com="Standard fuel assembly with 2 GPs on top left"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    3  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    3  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 13
  com="Standard fuel assembly with 2 GPs on top right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    3  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    3  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 21
  com="Standard fuel assembly with 1 B4C rod at top right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    4  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 22
  com="Standard fuel assembly with 1 B4C rod at top left"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    4  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 23
  com="Standard fuel assembly with 1 B4C rod at left"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    4  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 24
  com="Standard fuel assembly with 1 B4C rod at bottom left"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    4  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 25
  com="Standard fuel assembly with 1 B4C rod at bottom right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    4  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 26
  com="Standard fuel assembly with 1 B4C rod at right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    4  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 41
  com="Standard fuel assembly with 1 B4C rod at top left and 1 GP rod at top right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    3  origin x= 1.39065  y= 2.40868
     hole    4  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 42
  com="Standard fuel assembly with 1 B4C rod at right and 1 GP rod at bottom right"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    3  origin x= 1.39065  y=-2.40868
     hole    2  origin x=-1.39065  y=-2.40868
     hole    4  origin x= 2.78130  y= 0.00000
     hole    2  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 43
  com="Standard fuel assembly with 1 B4C rod at bottom left and 1 GP rod at left"
 rhexprism  10  4.02388   30.7450    0.0000  com="Na-grid plate"
 rhexprism  20  3.85834  145.3628   30.7450  com="Steel duct"
 rhexprism  30  4.01114  145.3628   30.7450  com="Inside duct"
 rhexprism  40  4.02388  145.3628   30.7450  com="Sodium gap"
 rhexprism  50  4.02388  165.6018  145.3628  com="Na-steel"
 rhexprism  60  4.02388  165.6018    0.0000  com="Outer boundary"
     media  35  1  10
     media  11  1  20
     media  22  1  30 -20
     hole    1
     hole    2  origin x= 1.39065  y= 2.40868
     hole    2  origin x=-1.39065  y= 2.40868
     hole    2  origin x= 1.39065  y=-2.40868
     hole    4  origin x=-1.39065  y=-2.40868
     hole    2  origin x= 2.78130  y= 0.00000
     hole    3  origin x=-2.78130  y= 0.00000
     hole    6  origin x= 0.00000  y= 3.47540
     hole    6  origin x= 0.00000  y=-3.47540
     hole    6  origin y= 1.73770  x= 3.00978
     hole    6  origin y=-1.73770  x= 3.00978
     hole    6  origin y= 1.73770  x=-3.00978
     hole    6  origin y=-1.73770  x=-3.00978
     media  11  1  40 -30
     media  36  1  50
  boundary  60 

unit 31
  com="Downcomer Inner Vessel"
 rhexprism  10  4.02388  165.6018    0.0000  com="Outer boundary"
     media  31  1  10
  boundary  10

global unit 100
  cylinder   10            53.48600  165.6018    0.0000  com="Downcomer OV"
  cylinder   11            58.26300  165.6018    0.0000  com="Core radius"
      ring   20  58.26300  73.55300   30.7450    0.0000  com="Steel void"
      ring   30  58.26300  73.55300  145.3628   30.7450  com="Reflector"
      ring   40  58.26300  73.55300  165.6018  145.3628  com="Steel void"
     plane   31  xpl= 0.577350  ypl=-1.00000  zpl=0.00000  con=0.00000 
     plane   32  xpl= 2.246040  ypl=-1.00000  zpl=0.00000  con=0.00000
     plane   33  xpl=-4.704630  ypl=-1.00000  zpl=0.00000  con=0.00000
     plane   34  xpl=-0.900404  ypl=-1.00000  zpl=0.00000  con=0.00000
     plane   35  xpl=-0.105104  ypl=-1.00000  zpl=0.00000  con=0.00000
     plane   36  xpl= 0.000000  ypl= 1.00000  zpl=0.00000  con=0.00000
     plane   37  xpl= 1.000000  ypl= 0.00000  zpl=0.00000  con=0.00000
  cylinder   50  87.03400            165.6018    0.0000 
     array   10  10  place 10 10 1 0.0 0.0 0.0
     media   32  1   11 -10
     media   37  1   20 -32 -33
     media   37  1   20  33 -34
     media   37  1   20 -31  32
     media   37  1   20  31 -35
     media   37  1   20 -34  35
     media   37  1   20 -33  34
     media   37  1   20  32  33
     media   37  1   20  31 -32
     media   37  1   20 -31  35
     media   37  1   20  34 -35
     media   33  1   30 -32 -33
     media   33  1   30  33 -34
     media   33  1   30 -31  32
     media   33  1   30  31 -35
     media   33  1   30 -34  35
     media   33  1   30 -33  34
     media   33  1   30  32  33
     media   33  1   30  31 -32
     media   33  1   30 -31  35
     media   33  1   30  34 -35
     media   37  1   40 -32 -33
     media   37  1   40  33 -34
     media   37  1   40 -31  32
     media   37  1   40  31 -35
     media   37  1   40 -34  35
     media   37  1   40 -33  34
     media   37  1   40  32  33
     media   37  1   40  31 -32
     media   37  1   40 -31  35
     media   37  1   40  34 -35
     media   34  1   50 -40 -30 -20 -11
  boundary   50
end geometry

read array
  ara=10
  prt=yes
  typ=rhexagonal
  nux=19
  nuy=19
  nuz=1
  fill
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 11 31 11 31 11 31 31 31 31 31 31 31
    31 31 31 31 31 11 11 11 11 21 11 11 11 11 31 31 31 31 31
    31 31 31 31 31 11 11 11 11 11 11 12 11 11 31 31 31 31 31
    31 31 31 31 11 21 11 11 41 11 11 11 11 11 11 31 31 31 31
    31 31 31 11 11 11 11 11 11 11 11 23 11 11 11 11 31 31 31
    31 31 31 11 11 13 11 23 11 10 11 11 11 11 21 11 31 31 31
    31 31 31 11 25 11 11 11 11 11 11 11 43 11 11 11 31 31 31
    31 31 31 31 11 11 11 42 11 11 21 11 11 23 11 31 31 31 31
    31 31 31 31 11 11 11 11 11 11 11 11 11 11 11 31 31 31 31
    31 31 31 31 31 11 23 11 24 11 11 25 11 11 31 31 31 31 31
    31 31 31 31 31 31 11 11 11 11 11 11 11 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
    31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31
  end fill
end array

read volume
 type=trace nrays=1e8
end volume

end data
end
(sfr/sefor/Shift_Reference/Core_I-E_450K.inp)

Listing 2: 

################################################################################
## NEAMS Fast Reactor Application Driver                                      ##
## SEFOR SHIFT Model of SEFOR Core I-E at 450 K                               ##
## Please contact the authors for issues:                                     ##
## - Dr. Donny Hartanto (hartantod.at.ornl.gov)                               ##
################################################################################
[PROBLEM]
name          "SEFOR Core I-E"
mode           kcode

[MODEL=SCALE]
input          Core_I-E_450K.inp
volume_cells   1.1     1.2     1.3     1.4     1.5     1.6     1.7     1.8
               2.1     2.2     2.3     2.4     2.5     2.6     2.7     2.8     2.9     2.10    2.11
               3.1     3.2     3.3     3.4     3.5     3.6     3.7     3.8     3.9     3.10    3.11
               4.1     4.2     4.3     4.4     4.5     4.6
               6.1
              10.1    10.2    10.3    10.4    10.5    10.6    10.7
              11.1    11.2    11.3    11.4    11.5
              12.1    12.2    12.3    12.4    12.5
              13.1    13.2    13.3    13.4    13.5
              21.1    21.2    21.3    21.4    21.5
              23.1    23.2    23.3    23.4    23.5
              24.1    24.2    24.3    24.4    24.5
              25.1    25.2    25.3    25.4    25.5
              31.1
              41.1    41.2    41.3    41.4    41.5
              42.1    42.2    42.3    42.4    42.5
              43.1    43.2    43.3    43.4    43.5
             100.2   100.3   100.4   100.5   100.6   100.7   100.8   100.9   100.10  100.11  100.12
             100.13  100.14  100.15  100.16  100.17  100.18  100.19  100.20  100.21  100.22  100.23
             100.24  100.25  100.26  100.27  100.28  100.29  100.30  100.31  100.32  100.33
volumes      3.5828950225519e+03 3.0878378153855e+04 3.5829053477285e+03 2.7411240738209e+01 1.7869558937340e+03 8.4249673753689e+03 1.5796348930494e+04 9.6860998263045e+03
             2.6380982275299e+04 2.3294979273986e+03 1.2822206710442e+05 2.3295244725458e+03 8.0265409345498e+03 2.3294544207632e+03 8.1984110403084e+04 2.3294299564306e+03 2.6380988105418e+04 9.6666846508514e+03 5.4473729801149e+04
             2.9452441710709e+02 2.6006077937830e+01 1.4315070929718e+03 2.6006572841967e+01 8.9610274405256e+01 2.6006569484722e+01 9.1529223001235e+02 2.6007017573777e+01 2.9452386935820e+02 1.0792244953904e+02 6.0816117459177e+02
             5.8904931631605e+02 2.6277740396412e+03 2.6233706235081e+03 5.8905072184116e+02 4.5571274888238e+01 1.2163194044928e+03
             2.3646108526278e+04
             1.7244728342620e+03 1.1878503026230e+03 1.2041173816116e+02 5.8475517664651e+02 5.0614679161420e+03 5.6172290816059e+02 4.7820853965749e+01
             1.5865112040790e+05 1.5755904787598e+05 4.3923935794459e+04 3.7394014646951e+03 1.0443775706800e+05
             1.7244696831186e+03 1.7126077778396e+03 4.7742380078457e+02 4.0652711637750e+01 1.1351953968562e+03
             1.7244728342620e+03 1.7126078994259e+03 4.7742108094547e+02 4.0643617070885e+01 1.1351938859701e+03
             6.8978632119732e+03 6.8503705467868e+03 1.9097631915991e+03 1.6257756261247e+02 4.5407717172515e+03
             6.8978733836371e+03 6.8504033032108e+03 1.9097165557206e+03 1.6257271238408e+02 4.5407614992931e+03
             1.7244661100586e+03 1.7125946544092e+03 4.7743025751732e+02 4.0640943010731e+01 1.1351897564263e+03
             3.4489444508485e+03 3.4252031625646e+03 9.5486265130192e+02 8.1296688186553e+01 2.2703882404459e+03
             4.7586910511589e+05
             1.7244769539287e+03 1.7125968625397e+03 4.7743310743733e+02 4.0643252642359e+01 1.1351945483744e+03
             1.7244649990453e+03 1.7126059936046e+03 4.7743533053974e+02 4.0639067040454e+01 1.1351881740273e+03
             1.7244731566547e+03 1.7126027392463e+03 4.7743718060764e+02 4.0637283839378e+01 1.1351911549451e+03
             2.7772426466854e+05 1.9467034767384e+04 1.9467064471864e+04 1.9467084070947e+04 1.9467032596858e+04 1.9467038741360e+04 1.9467028633067e+04 1.9467015238275e+04 1.9467047870133e+04 1.9467028618410e+04 1.9467052644900e+04
             7.2573334009035e+04 7.2573389702765e+04 7.2573479896608e+04 7.2573365491694e+04 7.2573443214763e+04 7.2573417728414e+04 7.2573350663066e+04 7.2573506038618e+04 7.2573361723636e+04 7.2573443442201e+04 1.2814876407330e+04
             1.2814885290855e+04 1.2814896009576e+04 1.2814865617281e+04 1.2814890350548e+04 1.2814892987523e+04 1.2814879727438e+04 1.2814906775841e+04 1.2814873195253e+04 1.2814876301518e+04 1.1262827191230e+06

[PHYSICS=ce]
ce_lib_path   "../ce_7.1_hdf.h5"
kappa_library "../kappa.h5"
mode           n
dbrc           off

[COMP]
output         true
sclib_path    "../scale.rev40.sclib"

[PHYSICS][BROADEN]
kinematics     true

[SOURCE=separable global_fission]
[SOURCE][SHAPE=global]

[SHIFT]
[SHIFT][TRANSPORTER]
verbosity      none

[SHIFT][KCODE]
num_histories_per_cycle  500000
num_cycles               500
num_inactive_cycles      50
initial_keff             1.0
entropy_mesh             automatic

[RUN=mpi]
np   64
(sfr/sefor/Shift_Reference/Core_I-E_450K_ENDF71.omn)

Geometry

Figure 1 (a) shows the horizontal cut view of a Shift model for Core I-E. The 10 radial reflector sectors were sandwiched between the outside radial shield and an inner homogenized cylindrical region representing part of the downcomer outside its reactor vessel (DC_OV). The center hexagonal lattice contains 109 fuel assemblies. The space between the fuel lattice and the DC_OV was a homogenized region representing the reactor downcomer within the reactor vessel (DC_IV).

Shift Monte Carlo model of SEFOR Core I-E with (a) X-Y view (b) X-Z view

Figure 1: Shift Monte Carlo model of SEFOR Core I-E with (a) X-Y view (b) X-Z view

Figure 2 (a) to (d) depict the detail geometry of a normal SA, a SA with 1 GP rod and 1 B4C rod, a SA with 2 GP rods or a SA with 1 BC rod (AFA) used in Core I-E.

Shift Monte Carlo model of SEFOR Core I-E fuel assemblies: (a) Standard Assembly (SA), (b) SA with a GP rod and a B$_4$C rod, (c) SA with 2 GP rods, and (d) AFA

Figure 2: Shift Monte Carlo model of SEFOR Core I-E fuel assemblies: (a) Standard Assembly (SA), (b) SA with a GP rod and a BC rod, (c) SA with 2 GP rods, and (d) AFA

Figure 1 (b) illustrates the unique segmented design of a standard SEFOR fuel rod in SEFOR. Each rod incorporated nickel reflectors at both ends, depleted UO2 insulation layers separating the MOX fuel into segments. To mitigate reactivity feedback from fuel axial expansion, all standard fuel rods including GP rods included a central spring to create an expansion gap. This design feature was essential for reducing reactivity feedback from fuel axial expansion and accurately measuring reactivity feedback from the fuel Doppler effect. Neutronic models (Shift and Griffin) used a VOID region to describe the spring region.