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NESC0510 VIM2/15.

VIM, 3-D Monte-Carlo Analysis of Fast Critical Assemblies Using Point Cross-Sections

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1. NAME OR DESIGNATION OF PROGRAM:  VIM2/15.
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2. COMPUTERS
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Program name Package id Status Status date
VIM-2/13 NESC0510/05 Tested 03-FEB-1984

Machines used:

Package ID Orig. computer Test computer
NESC0510/05 IBM 3081 IBM 3081
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3. DESCRIPTION OF PROBLEM OR FUNCTION

VIM solves the three- dimensional steady-state multiplication eigenvalue or fixed source neutron or photon (VIM2/15) transport problem using continuous energy-dependent nuclear data. It was designed for the analysis of fast critical experiments. In VIM2/15, the photon interactions i.e., pair production, coherent and incoherent scattering, and photoelectric events, and photon heating are tallied by group, region, and isotope.
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4. METHOD OF SOLUTION

VIM uses the Monte Carlo technique to estimate  eigenvalues by collision, track length, and analog methods. Geometry options include infinite medium, plate cell lattice, general combinatorial geometry, and repeating lattices of hexagonal or rectangular cells constructed using combinatorial geometry. ENDF/B cross section data are used, including thermal scattering law data.  Variance reduction options available include several splitting and Russian roulette techniques, any linear combination of analog and absorption neutron weighting, and combined eigenvalue estimators. An easy-to-use restart option is also available.
In VIM2/15, photon cross sections are defined by composition independent microscopic datasets in the energy range from 1 KeV to 100 MeV. Coherent and incoherent scattering, pair production, and photoelectric cross section data are described by pointwise values with log-log interpolation. Photon heating numbers are specified pointwise with linear-log interpolation. Pair production is simulated by creation of a double-weighted photon of energy 0.511008 MeV, and production by fluorescence is treated explicitly. The Klein-Nishina distribution is sampled exactly for secondary angle and energy during incoherent scattering events.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM:  Maximum of -, 40 isotopes
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6. TYPICAL RUNNING TIME

The running time of VIM varies widely with problem characteristics. It depends linearly on the number of isotopes and is also dependent on the number of geometrical zones and the desired statistics. A small problem may run in 10 seconds per batch of 1000 neutron histories on the IBM370/195. NESC executed the VIM2/15 sample problem in approximately 1.2 CPU hours on an IBM4331.
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7. UNUSUAL FEATURES OF THE PROGRAM

VIM uses continuous energy cross section data with very fine energy detail rather than multigroup cross sections. It has been extensively benchmarked on fast reactor  problems using both experimental measurements and analytical comparisons.
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8. RELATED AND AUXILIARY PROGRAMS

The original WIM system was developed at Atomic International by L.B. Levitt and R.C. Lewis. The package includes a number of auxiliary codes:
NESC0510/05
XSEDIT BCD-to-binary or binary-to-BCD cross section                     editing program
FILEONE             cross  section library preparation  code  for
                    variable dimensioning
BANDIT              selects the isotopes for a specific  set  of
                    problems and splits the cross section data into
                    energy bands to reduce memory requirements
RETALLY             reprocesses VIM history data, collapsing the
                    edit energy groups and homogenizing regions for
                    processing selected batches
KEFCODE             reedits the eigenvalue estimators for a subset
                    of batches
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9. STATUS
Package ID Status date Status
NESC0510/05 03-FEB-1984 Tested at NEADB
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10. REFERENCES

- L.J. Milton:
  VIM Users' Guide
  ANL Applied Physics Division Memorandum, June 24, 1981.
- VIM2/13. NESC No. 510.7600, VIM2/13 CDC Version Tape Description
  and Implementation Information,
  NESC Note 85-23, October 31, 1984, Rev August 21, 1986.
- R.N. Blomquist:
  VIM Users' Guide
  ANL Applied Physics Division Memorandum, November 14, 1986.
- R.E. Prael:
  Cross Section Preparation for the Continuous-Energy Monte Carlo
  Code VIM
  Proc. Conf. on Nuclear Cross Sections and Technology,
  March 3-7, 1975, NBS Special Publication 425, pp. 447-450.
- R.E. Prael and H. Henryson II:
  A Comparison of VIM and MC**2-2 - Two Detailed Solutions of the
  Neutron Slowing-Down Problem
  Proc. Conf. on Nuclear Cross Sections and Technology
  March 3-7, 1975, NBS Special Publication 425, pp. 451-454.
- L.B. Levitt, R.C. Lewis:
  VIM1, A Non-multigroup Monte Carlo Code for Analysis of Fast
  Critical Assemblies
  AI-AEC-12951, May 15, 1970.
- VIM2/15, NESC No. R510.3033B, VIM2/15 Edition B Tape Description,
  and Implementation Information
  NESC Note 90-130, September 28, 1990.
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11. MACHINE REQUIREMENTS

Variable dimensioning is used throughout VIM. A small problem requires 600 Kbytes on the IBM3033. Storage requirements depend linearly on the number of isotopes in the problem and also on the edit detail in space and energy. VIM2/15 requires at least 750 Kbytes of memory.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0510/05 FORTRAN+ASSEMBLER
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE 2.1.5 (CDC7600), VMS (IBM3033), VM/CMS (IBM4331).
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS:
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15. NAME AND ESTABLISHMENT OF AUTHOR

VIM2/13       R.E. Prael and L.J. Milton

VIM2/15       R.N. Blomquist
               Applied Physics Division
               Argonne National Laboratory
               9700 South Cass Avenue
               Argonne, Illinois, 60439, U. S. A.
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16. MATERIAL AVAILABLE
NESC0510/05
File name File description Records
NESC0510_05.003 VIM-2/13 INFORMATION FILE 81
NESC0510_05.004 VIM-2/13 JCL 1418
NESC0510_05.005 VIM-2/13 SOURCE PROGRAM (FTN-4 & ASSEMBLER) 24605
NESC0510_05.006 VIM LINKEDT INPUT (JOB4A) 38
NESC0510_05.007 BANDIT LINKEDT INPUT (JOB9) 9
NESC0510_05.008 RETALLY LINKEDIT INPUT (JOB12) 18
NESC0510_05.009 FILEONE INPUT (JOB8) 110
NESC0510_05.010 XSEDIT INPUT FOR BCD-BIN CONVERSION 10
NESC0510_05.011 BANDIT INPUT FOR TEST CASE (JOB10) 2
NESC0510_05.012 VIM INPUT FOR TEST CASE (JOB11) 51
NESC0510_05.013 FILEONE OUTPUT OF TEST CASE (JOB8) 457
NESC0510_05.014 BANDIT OUTPUT OF TEST CASE (JOB10) 1354
NESC0510_05.015 VIM OUTPUT OF TEST CASE (JOB11) 8939
NESC0510_05.016 RETALLY OUTPUT OF TEST CASE (JOB13) 652
NESC0510_05.017 KEFCODE OUTPUT OF TEST CASE (JOB15) 119
NESC0510_05.018 USER'S GUIDE 9941
NESC0510_05.019 ENDF/B-4 X-SEC FOR 100 MATERIALS 274645
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17. CATEGORIES
  • C. Static Design Studies

Keywords: ENDF/B, Monte Carlo method, ZPPR reactors, ZPR-3 reactors, cell calculation, criticality, hexagonal lattices, neutron transport theory, photon transport, reactor lattices, shielding, slowing-down, zebra reactors.