NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROGRAM OR FUNCTION, METHOD OF SOLUTION, RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM, TYPICAL RUNNING TIME, UNUSUAL FEATURES OF THE PROGRAM, RELATED AND AUXILIARY PROGRAMS, STATUS, REFERENCES, REQUIREMENTS, LANGUAGE, OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED, OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHORS, MATERIAL, CATEGORIES

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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 |
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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.

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.

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.

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.

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.[ top ]

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.

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.)

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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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).

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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NEA-0900/03

File name | File description | Records |
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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 |

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