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NEA-0616 KIM.

KIM, Steady-State Transport for Fixed Source in 2-D Thermal Reactor by Monte-Carlo

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1. NAME OR DESIGNATION OF PROGRAM:  KIM.
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2. COMPUTERS
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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.
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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.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

Not more than 50 regions. Maximum number of materials 12, with no more than 10 nuclides each. The total number of nuclides in the whole assembly cannot exceed 20, with 8 fissile nuclides.
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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.
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7. UNUSUAL FEATURES OF THE PROGRAM:  A special geometry treatment.
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8. RELATED AND AUXILIARY PROGRAMS

The libraries distributed together  with the code are generated by using evaluated nuclear data file processing codes. These libraries contain data processed from UKNDL and ENDF/B-IV (the specific data origin is printed by each run of the code).
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9. STATUS
Package ID Status date Status
NEA-0616/01 01-MAY-1980 Tested at NEADB
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10. REFERENCES

- "KIM, A Two-Dimensional Monte Carlo Program for Thermal Reactors"
  CNEN RT/FIMA... (1980) (to be published).
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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.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-0616/01 FORTRAN+ASSEMBLER
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  IBM 370 MVS or MVT.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

Exploitation of the half-word addressability can be easily eliminated at the only expense of an increase of memory requirement.
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15. NAME AND ESTABLISHMENT OF AUTHOR

          E. Cupini, A. De Matteis, R. Simonini
          CNEN, Centro Calcolo
          Via Mazzini 2
          Bologna, Italy.
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16. MATERIAL AVAILABLE
NEA-0616/01
File name File description Records
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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17. CATEGORIES
  • 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.