Computer Programs

NAME OR DESIGNATION OF PROGRAM, COMPUTER, DESCRIPTION OF PROBLEM 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, MACHINE REQUIREMENTS, LANGUAGE, OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED, OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS, NAME AND ESTABLISHMENT OF AUTHOR, MATERIAL, CATEGORIES

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Program name | Package id | Status | Status date |
---|---|---|---|

KIM | NEA-0616/01 | Tested | 01-MAY-1980 |

Machines used:

Package ID | Orig. computer | Test computer |
---|---|---|

NEA-0616/01 | IBM 3033 |

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3. DESCRIPTION OF PROBLEM OR FUNCTION

KIM (K-infinite Monte Carlo) is a program which solves the steady-state linear transport equation for a fixed-source problem (or, by successive fixed-source runs, for the eigenvalue problem) in a two-dimensional infinite thermal reactor lattice. The main quantities computed in some broad energy groups are the following:

- Fluxes and cross sections averaged over the region (i.e. a space portion that can be unconnected but contains everywhere the same homogeneous material), grouping of regions, the whole element.

- Average absorption and fission rates per nuclide.

- Average flux, absorption and production distributions versus energy.

KIM (K-infinite Monte Carlo) is a program which solves the steady-state linear transport equation for a fixed-source problem (or, by successive fixed-source runs, for the eigenvalue problem) in a two-dimensional infinite thermal reactor lattice. The main quantities computed in some broad energy groups are the following:

- Fluxes and cross sections averaged over the region (i.e. a space portion that can be unconnected but contains everywhere the same homogeneous material), grouping of regions, the whole element.

- Average absorption and fission rates per nuclide.

- Average flux, absorption and production distributions versus energy.

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4. METHOD OF SOLUTION

Monte Carlo simulation is used by tracing particle histories from fission birth down through the resonance region until absorption in the thermal range. The program is organised in three sections for fast, epithermal and thermal simulation, respectively; each section implements a particular model for both numerical techniques and cross section representation (energy groups in the fast section, groups or resonance parameters in the epithermal section, points in the thermal section).

During slowing down (energy above 1 eV) nuclei are considered as stationary, with the exception of some resonance nuclei whose spacing between resonances is much greater than the resonance width. The Doppler broadening of s-wave resonances of these nuclides is taken into account by computing cross sections at the current neutron energy and at the temperature of the nucleus hit.

During thermalisation (energy below 1 eV) the thermal motion of some nuclides is also considered, by exploiting scattering kernels provided by the library for light water, heavy water and oxygen at several temperatures.

KIM includes splitting and Russian roulette.

A characteristic feature of the program is its approach to the lattice geometry. In fact, besides the usual continuous treatment of the geometry using the well-known "combinatorial" description (adapted to planar domains), the program allows complex configurations to be represented by a discrete set of points, whereby the calculation speed is greatly improved. In this second approach configurations are described as the result of successive overlays of elementary figures over a basic domain.

Monte Carlo simulation is used by tracing particle histories from fission birth down through the resonance region until absorption in the thermal range. The program is organised in three sections for fast, epithermal and thermal simulation, respectively; each section implements a particular model for both numerical techniques and cross section representation (energy groups in the fast section, groups or resonance parameters in the epithermal section, points in the thermal section).

During slowing down (energy above 1 eV) nuclei are considered as stationary, with the exception of some resonance nuclei whose spacing between resonances is much greater than the resonance width. The Doppler broadening of s-wave resonances of these nuclides is taken into account by computing cross sections at the current neutron energy and at the temperature of the nucleus hit.

During thermalisation (energy below 1 eV) the thermal motion of some nuclides is also considered, by exploiting scattering kernels provided by the library for light water, heavy water and oxygen at several temperatures.

KIM includes splitting and Russian roulette.

A characteristic feature of the program is its approach to the lattice geometry. In fact, besides the usual continuous treatment of the geometry using the well-known "combinatorial" description (adapted to planar domains), the program allows complex configurations to be represented by a discrete set of points, whereby the calculation speed is greatly improved. In this second approach configurations are described as the result of successive overlays of elementary figures over a basic domain.

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6. TYPICAL RUNNING TIME

The time needed on the IBM 370/168 to obtain the infinite multiplication factor with s.d. of about 0.3% for a typical 8 x 8 rod element of a BWR is about 40 min., corresponding to 40,000 histories. This time refers to a geometry treated in the discrete mode, while the continuous mode requires almost double the time.

The time needed on the IBM 370/168 to obtain the infinite multiplication factor with s.d. of about 0.3% for a typical 8 x 8 rod element of a BWR is about 40 min., corresponding to 40,000 histories. This time refers to a geometry treated in the discrete mode, while the continuous mode requires almost double the time.

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11. MACHINE REQUIREMENTS

Core storage is dependent on the complexity of the problem. Dynamic storage allocation at running time is used for the most critically-sized arrays, like thermalisation kernels and the map of the discretised domain. For complex cases about 1000 K bytes might be needed. As a minimum, one tape unit for the libraries and two scratch files are required. One more scratch file and one more permanent unit are needed to file and/or to restart a calculation. A CPU time clock is used.

Core storage is dependent on the complexity of the problem. Dynamic storage allocation at running time is used for the most critically-sized arrays, like thermalisation kernels and the map of the discretised domain. For complex cases about 1000 K bytes might be needed. As a minimum, one tape unit for the libraries and two scratch files are required. One more scratch file and one more permanent unit are needed to file and/or to restart a calculation. A CPU time clock is used.

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NEA-0616/01

File name | File description | Records |
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NEA0616_01.001 | FORTRAN SOURCE | 10684 |

NEA0616_01.002 | TIMING ASSEMBLER SOURCE | 656 |

NEA0616_01.003 | DYNAMIC STORAGE ALLOCATION ASS. SOURCE | 279 |

NEA0616_01.004 | TIMING ASSEMBLER SOURCE | 113 |

NEA0616_01.005 | LINK-EDIT OVERLAY CARDS | 23 |

NEA0616_01.006 | THERMAL LIBRARY | 60843 |

NEA0616_01.007 | EPITHERMAL LIBRARY | 3364 |

NEA0616_01.008 | FAST LIBRARY | 2319 |

NEA0616_01.009 | S. P. INPUT DATA | 596 |

NEA0616_01.010 | S. P. PRINTED OUTPUT | 5252 |

NEA0616_01.011 | JCL,CONTROL CARDS | 149 |

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- B. Spectrum Calculations, Generation of Group Constants and Cell Problems
- C. Static Design Studies

Keywords: Doppler broadening, Monte Carlo method, absorption, cross sections, epithermal neutrons, fast neutrons, fission, neutron flux, neutron transport equation, reactor lattices, steady-state conditions, thermal neutrons, thermal reactors, transport theory, two-dimensional.