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NEA-0900 TPHEX

TPHEX, MultiGroup Neutron Flux in Homogeneous Hexagonal LWR Cells

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1. NAME OR DESIGNATION OF PROGRAM:  TPHEX
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2. COMPUTERS
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Program name Package id Status Status date
TPHEX NEA-0900/03 Tested 14-SEP-1993

Machines used:

Package ID Orig. computer Test computer
NEA-0900/03 CRAY X-MP CRAY-XMS
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3. DESCRIPTION OF PROGRAM OR FUNCTION

This program is intended to calculate the multigroup neutron flux distribution in an assembly of homogenized hexagonal cells using a transmission probability (interface current) method. It is primarily intended for calculations on hexagonal LWR fuel assemblies, with each cell corresponding to a pin cell, but can be used for other purposes, although its accuracy in other applications must be established separately. The flux at each cell interface is divided azimuthally into 60-degree sectors, with two components (an incomplete P1 expansion) in each sector. The interface fluxes are connected by transmission of uncollided neutrons through the cell. AN isotropic source (from fission or scattering) within the cell with a parabolic spatial distribution also contributes. The boundary conditions may correspond to full reflection at the midplanes of the peripheral cells or (approximately) to a diagonal albedo matrix. Periodic boundary conditions can easily be implemented. If the peripheral cells are not regular hexagons, an edge transport correction may be  applied to decrease the error from treating them as regular.
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4. METHOD OF SOLUTION

The flux in one group is solved in an inner iteration, which may be accelerated by successive overrelaxation and, optionally, renormalization. The fluxes in different groups, connected through scattering and fission, are solved by outer iteration.
The coefficients needed by the program (transmission coefficients etc.) are interpolated from precalculated values stored in a file.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The optical thickness of the cells must be in the range from 0.1 to 5. These limits can be expanded if the coefficient file is recalculated, but  the accuracy is best when the optical thickness is not too near the  ends of this range.
Variable dimensioning is used, so there are no fixed limits on the number of cells or groups. However, since 48 variables are needed to describe the flux and source in each cell and group, and since many  coefficients are also needed, large problems (more than about 225 cells) may require lots of memory, even though only data for one group at a time are held in memory.
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6. TYPICAL RUNNING TIME

Somewhat less than 1 minutes on a UNIVAC 1108 for 36 cells and 7 groups. As a rule of thumb, TPHEX takes about 5
times as long as a diffusion program but less than 1.10 of the time of a collision probability program.
NEA-0900/03
The four test cases included in this package have been  run by NEA-DB on a Cray-XMS computer in a total of 22 seconds of CPU time.
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7. UNUSUAL FEATURES OF THE PROGRAM

TPHEX was developed for use as a 2-D module in the assembly burnup program CASMO-HEX and was intended to be more accurate than a diffusion program and faster than a collision probability (CP) program in the calculation of the flux distribution within a fuel assembly. This aim was achieved, and in practice it also turned out to give more accurate results than the CP module in CASMO-HEX.
Since TPHEX was not intended for use as a stand-alone program, little attention was paid to user convenience in programming the input. Any user who intends to use TPHEX extensively as a stand-alone program would be well advised to reprogram the input.
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8. RELATED AND AUXILIARY PROGRAMS

SNOOPY snoops out relevant data from the TPHEX iteration debug output file.
TPHEXTR may be used to accelerate convergence through extrapolation  in cases where the convergence is very slow (such as large systems of optically thick cells). If this is needed often, it should be incorporated in TPHEX itself. We have not found this necessary for normal applications.
TPHXPND can be used to obtain pointwise rather than cell average fluxes from the parabolic expansion used within each cell. (This should be used critically, the resulting flux distributions are not  necessarily accurate, especially not if the cell is actually heterogeneous.)
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9. STATUS
Package ID Status date Status
NEA-0900/03 14-SEP-1993 Tested at NEADB
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10. REFERENCES

F. Wasastjerna: An Application of the Transmission
Probability Method to the Calculation of Neutron Flux Distributions
in Hexagonal Geometry. Nuclear Science and Engineering, 72, 9-18
(1979).
NEA-0900/03, included references:
- F. Wasastjerna:
  TPHEX User's Manual
  Nuclear Engineering Laboratory, Technical Research Centre of
  Finland, Helsinki
  Report 47 (March 1980).
- F. Wasastjerna:
  TPCURR-T, A Program for Printing Cell-to-Cell Partial Currents
  Calculated by the Stand-Alone Version of TPHEX
  REP-5/82 (March 1982).
- F. Wasastjerna:
  TPCURR-T2, A Program for Printing Cell-to-Cell Partial Currents
  Calculated by the Stand-Alone Version of TPHEX
  REP-17/85 (August 1985).
- F. Wasastjerna and I. Lux:
  TPHEX Programmer's Manual
  Nuclear Engineering Laboratory, Report 149 (October 1982).
- F. Wasastjerna:
  Validation of TPHEX
  REP-22/85 (November 1985).
- F. Wasastjerna:
  An Application of the Transmission Probability Method to the
  Calculation of Neutron Flux Distributions in Hexagonal Geometry
  Reprint Nuclear Science and Engineering 72, 9-18 (1979).
- F. Wasastjerna and I. Lux:
  A Transmission Probability Method for Calculation of Neutron Flux
  Distributions in Hexagonal Geometry
  Nuclear Engineering Laboratory, Report 46 (March 1980).
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11. HARDWARE REQUIREMENTS

MACHINE REQUIREMENTS: 64 K words or more of memory, back-up storage  on discs or other media and a line printer. Clock calls are present  in TPHEX but can be omitted if necessary.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0900/03 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED

NEA 0900/03: The test cases have been run on Cray-XMS under UNICOS-6.1. The source program was compiled using the CFT77 compiler.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHORS

     Frej WASASTJERNA
     Nuclear Engineering Laboratory
     Technical Research Centre of Finland
     P.O. Box 208
     F-02151 ESPOO, Finland
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16. MATERIAL AVAILABLE
NEA-0900/03
File name File description Records
NEA0900_03.001 Information file 69
NEA0900_03.002 JCL to compile, link and run TPHEX code 20
NEA0900_03.003 TPHEX.F - FORTRAN 77 source for TPHEX 3513
NEA0900_03.004 TABU - table of coefficients 4078
NEA0900_03.005 INP1 - TPHEX sample input 1 77
NEA0900_03.006 INP2 - TPHEX sample input 2 30
NEA0900_03.007 INP3 - TPHEX sample input 3 31
NEA0900_03.008 INP4 - TPHEX sample input 4 37
NEA0900_03.009 OUT1 - TPHEX sample output 1 297
NEA0900_03.010 OUT2 - TPHEX sample output 2 584
NEA0900_03.011 OUT3 - TPHEX sample output 3 151
NEA0900_03.012 OUT4 - TPHEX sample output 4 166
NEA0900_03.013 SNOOPY.F FORTRAN debugger source program 521
NEA0900_03.014 TPHEXTR.F FORTRAN source program 89
NEA0900_03.015 TPHEPND.F FORTRAN source program 231
NEA0900_03.016 TPCURR.F FORTRAN 77 source program 192
NEA0900_03.017 TPCURR.INP input to TPCURR 7
NEA0900_03.018 TPCURR.OUT output from TPCURR 71
NEA0900_03.019 FLUX - flux output from TPHEX 86
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17. CATEGORIES
  • C. Static Design Studies

Keywords: LWR reactors, flux distribution, hexagonal lattices, neutron flux.