CHOPS.rst 6.41 KB
 Batson Iii committed Nov 17, 2020 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 .. _7-6: CHOPS: Module to Compute Pointwise Disadvantage Factors and Produce a Cell-Homogenized CENTRM Library ===================================================================================================== *M. L. Williams and L. M. Petrie* .. _7-6-1: Introduction ------------ CHOPS (**C**\ ompute **HO**\ mogenized **P**\ ointwise **S**\ tuff) computes pointwise (PW) disadvantage factors from the PW zone fluxes on a CENTRM output file, and then multiples the disadvantage factors by continuous-energy (CE) cross section data in a CENTRM library to generate a new cell-homogenized CENTRM CE library. The PW disadvantage factor for zone “Z”, as a function of energy E, is calculated from the expression, .. math:: :label: eq7-6-1 D_{Z}(E)=\frac{\Phi_{Z}(E)}{\Phi_{C}(E)} where :math:\Phi_{Z}(E) is the CENTRM PW flux spectrum averaged over the volume of zone Z in the cell, and :math:\Phi_{C}(E) is the PW flux averaged over the entire cell volume. The cell-homogenized CE cross section for a nuclide “j” is equal to .. math:: :label: eq7-6-2 \sigma_{C}^{(j)}(E)=\sum_{Z} F_{Z}^{(j)} D_{Z}(E) \sigma_{Z}^{(j)}(E) where :math:F_{Z}^{(j)} is the fraction of all nuclide–j atoms contained in zone Z, and :math:\sigma_{Z}^{(j)}(E) is the CE cross section for nuclide-j at the temperature of zone Z. When multiplied by the cell-homogenized number density of nuclide-j and by the cell-average flux, the cross section expression in :eq:eq7-6-1 gives the correct average reaction rate at energy E. .. equation in here says 8.5.1 CHOPS is used in the automated double heterogeneity sequence in SCALE, in which a low-level heterogeneity, such as microspheres in a granular fuel element, are smeared into a homogenized absorber region appearing in the second level heterogeneity, such as fuel pellet or pebble appearing in a lattice. The disadvantage factors provide for flux weighting of the PW XS data so that the spatial self-shielding is treated correctly in the homogenized geometry. A second CENTRM PW transport calculation is performed with the cell-averaged PW library output by CHOPS in order to account for the additional self-shielding of the absorber pellets/pebbles in the lattice. CHOPS is called automatically by the XSProc module for double-heterogeneous unit cells, or it can run as a standalone code. .. _7-6-2: CHOPS Input Data ---------------- **DATA BLOCK 1** **0$$LOGICAL UNIT ASSIGNMENTS** (10 entries. Default values given in parentheses) 1. lold -- logical unit number of input CENTRM XS library (1) 2. lnew -- logical unit number of output CENTRM homogenized XS library (2) 3. lflx -- logical unit number of input CENTRM PW flux library (3) 4. ldis -- logical unit number for edit of PW disadvantage factors (0) 5. n15 -- logical unit number for scratch (15) 6. n16 -- logical unit number for scratch (16) 7. n17 -- logical unit number for scratch (17) 8. n18 -- logical unit number for scratch (18) 9. n19 -- logical unit number for scratch (19) 10. nsq -- sequence number used in filename on unit “lnew” (1) [Example: if *lnew=11* and *nsq=3*: output filename of homogenized library\ *= ft11f003]* **1$$ INTEGER PARAMETERS** (5 entries ) 1. idtap -- identifier for the new library (55555) [for macro library, the value of *idtap* is made negative] 2. nprt -- output print option: 0 = > min print; 1 = > normal; 2 = > max print (0) 3. iden -- if=0 = > define homogenized XS id = id on CENTRM flux file (0) if>0 = > define homogenized XS id to be, (*iden*\ \*10\ :sup:6 + ZA) 4. macr -- type of XS output: 0 = > microscopic ; 1 = > macroscopic (0) 5. icorr -- not used (0) **2*\* REAL PARAMETERS** (3 entries ) 1. tole -- tolerance used to thin pointwise cross-sections (0.0025) ( 0.0 means no thinning is done ) 2. cleth -- maximum lethargy between thinned pointwise cross-sections points that allow a point to be discarded (0.25) 3. vfrac -- multiplier applied to all output XS’s [eg, grain fraction] (1.0) T [ TERMINATE DATA BLOCK 1 ] .. _7-6-3: CHOPS I/O units --------------- :numref:tab7-6-1 shows default logical unit numbers used by CHOPS. These values may be changed in the 0array of input. .. _tab7-6-1: .. table:: Default I/O unit assignments for CHOPS. :align: center +-------------+-------------------------------------------+ | Unit number | Description | +-------------+-------------------------------------------+ | 1 | Input CENTRM CE data library | | | | | 2 | Output homogenized CENTRM CE data library | | | | | 3 | Input pointwise CENTRM flux file | | | | | 15 | Scratch file | | | | | 16 | Scratch file | | | | | 17 | Scratch file | | | | | 18 | Scratch file | | | | | 19 | Scratch file | +-------------+-------------------------------------------+ .. _7-6-4: CHOPS Sample Input ------------------ The sample case in :numref:list7-6-1 first executes a CENTRM unit cell geometry calculation using the CSAS-MG sequence, which by default generates the PW flux file on unit 15, as well as the CE nuclear data library on unit 81 for input to CHOPS. The standalone CHOPS code then computes a cell-homogenized CE library for the unit cell. The new homogenized CENTRM CE library is output on unit 91with filename: *ft91f001* .. code-block:: scale :caption: CHOPS sample input. :name: list7-6-1 =CSAS-MG parm=centrm test case for CHOPS v7-252n READ COMP ' Fuel pellet o 1 0 4.59675e-2 900.0 end u-235 1 0 4.88385e-4 900.0 end u-238 1 0 2.24804e-2 900.0 end ' Clad zr 2 0 4.99789e-2 600.0 end ' Coolant h 3 0 4.76619e-2 600.0 end o 3 0 2.38310e-2 600.0 end END COMP READ CELLDATA latticecell squarepitch pitch=1.6 3 fueld=1.262 1 cladd=1.350 2 end END CELLDATA END =CHOPS 0 81 91 15 93 92 e 1 a2 1 e 2** a3 1.0 e t END